User Manual

User Manual
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User Manual
FieldForce TCM
High Accuracy Electronic Compass Module
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Table of Contents
1 COPYRIGHT & WARRANTY INFORMATION ................................................. 1
2 INTRODUCTION ......................................................................................... 2
3 SPECIFICATIONS ......................................................................................... 3
3.1
Performance Specifications .................................................................. 3
3.2
Operating Characteristics ..................................................................... 4
3.3
Mechanical Drawing ............................................................................. 5
4 SET-UP ....................................................................................................... 7
4.1
Electrical Connections ........................................................................... 7
4.2
Installation Location.............................................................................. 8
4.2.1
Operate within sensors’ linear regime ........................................ 8
4.2.2
Locate away from changing magnetic fields ............................... 8
4.2.3
Mount in a physically stable location .......................................... 8
4.2.4
Location-verification testing ........................................................ 8
4.3
Mechanical Mounting ........................................................................... 9
5 OPERATION WITH TCM STUDIO ............................................................... 10
5.1
Installation onto a Windows or Mac System ...................................... 10
5.2
Connection Tab ................................................................................... 11
5.2.1
Initial Connection ....................................................................... 11
5.2.2
Changing Baud Rate ................................................................... 11
5.2.3
Changing Modules ..................................................................... 12
5.3
Configuration Tab ............................................................................... 12
5.3.1
Mounting Options ...................................................................... 12
5.3.2
North Reference......................................................................... 13
5.3.3
Endianess ................................................................................... 13
5.3.4
Output ........................................................................................ 13
5.3.5
Enable 3D Model ........................................................................ 14
5.3.6
Filter Setting (Taps) .................................................................... 14
5.3.7
Acquisition Settings.................................................................... 14
5.3.8
HPR During Calibration .............................................................. 15
5.3.9
Calibration Settings .................................................................... 15
5.3.10 Default........................................................................................ 16
5.3.11 Retrieve ...................................................................................... 16
5.4
Calibration Tab .................................................................................... 17
5.4.1
Samples ...................................................................................... 17
5.4.2
Calibration Results ..................................................................... 18
5.4.3
Current Configuration ................................................................ 19
5.4.4
Options ....................................................................................... 19
5.4.5
Clear ........................................................................................... 19
5.5
Test Tab ............................................................................................... 20
5.5.1
Current Reading ......................................................................... 20
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5.5.2
3D Model.................................................................................... 20
5.5.3
Acquisition Settings.................................................................... 20
5.5.4
Sync Mode.................................................................................. 21
5.6
Data Logger Tab .................................................................................. 22
5.7
System Log Tab ................................................................................... 23
5.8
Graph Tab............................................................................................ 24
6 FIELD CALIBRATION ................................................................................. 25
6.1
Magnetic Field Calibration Theory...................................................... 26
6.1.1
Hard and Soft Iron Effects .......................................................... 26
6.1.2
Pitch and Roll ............................................................................. 26
6.2
Field Calibration Procedures ............................................................... 27
6.2.1
Full Range Calibration ................................................................ 28
6.2.2
2D Calibration ............................................................................ 31
6.2.3
Limited Tilt Range Calibration .................................................... 32
6.2.4
Hard Iron Only Calibration ......................................................... 33
6.2.5
Accelerometer Only Calibration ................................................ 33
6.2.6
Mag and Accel Calibration ......................................................... 35
6.3
Declination Value ................................................................................ 35
6.4
Other Considerations .......................................................................... 35
7 OPERATION WITH PNI BINARY PROTOCOL ............................................... 36
7.1
Datagram Structure ............................................................................ 36
7.2
Parameter Formats ............................................................................. 37
7.3
Commands & Communication Frames ............................................... 39
7.4
kGetModInfo (frame ID 1d) ................................................................ 40
7.4.1
kModInfoResp (frame ID 2d) ..................................................... 40
7.4.2
kSetDataComponents (frame ID 3d) .......................................... 40
7.4.3
kGetData (frame ID 4d) .............................................................. 42
7.4.4
kDataResp (frame ID 5d) ............................................................ 42
7.4.5
kSetConfig (frame ID 6d) ............................................................ 43
7.4.6
kGetConfig (frame ID 7d) ............................................................ 46
7.4.7
kConfigResp (frame ID 8d) .......................................................... 46
7.4.8
kSave (frame ID 9d) .................................................................... 46
7.4.9
kStartCal (frame ID 10d) ............................................................ 47
7.4.10 kStopCal (frame ID 11d) ............................................................. 48
7.4.11 kSetParam (frame ID 12d) .......................................................... 48
7.4.12 kGetParam (frame ID 13d).......................................................... 50
7.4.13 kParamResp (frame ID 14 d) ....................................................... 50
7.4.14 kPowerDown (frame ID 15 d) ..................................................... 50
7.4.15 kSaveDone (frame ID 16 d) ......................................................... 50
7.4.16 kUserCalSampCount (frame ID 17 d) .......................................... 51
7.4.17 kUserCalScore (frame ID 18 d) .................................................... 51
7.4.18 kSetConfigDone (frame ID 19 d) ................................................. 52
7.4.19 kSetParamDone (frame ID 20 d) ................................................. 52
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7.4.20 kStartIntervalMode (frame ID 21 d) ........................................... 52
7.4.21 kStopIntervalMode (frame ID 22 d) ............................................ 52
7.4.22 kPowerUp (frame ID 23 d) .......................................................... 52
7.4.23 kSetAcqParams (frame ID 24 d) .................................................. 52
7.4.24 kGetAcqParams (frame ID 25 d) ................................................. 53
7.4.25 kAcqParamsDone (frame ID 26 d) .............................................. 54
7.4.26 kAcqParamsResp (frame ID 27 d) ............................................... 54
7.4.27 kPowerDownDone (frame ID 28 d) ............................................. 54
7.4.28 kFactoryUserCal (frame ID 29 d) ................................................. 54
7.4.29 kFactoryUserCalDone (frame ID 30 d) ........................................ 54
7.4.30 kTakeUserCalSample (frame ID 31 d) ......................................... 54
7.4.31 kFactoryInclCal (frame ID 36 d)................................................... 54
7.4.32 kFactoryInclCalDone (frame ID 37 d) .......................................... 54
7.4.33 kSetMode (frame ID 46 d)........................................................... 55
7.4.34 kSetModeResps (frame ID 47 d) ................................................. 55
7.4.35 kSyncRead (frame ID 49 d) .......................................................... 56
7.5
Code Examples .................................................................................... 57
7.5.1
Header File & CRC-16 Function .................................................. 57
7.5.2
CommProtocol.h File ................................................................. 60
7.5.3
CommProtocol.cpp File .............................................................. 62
7.5.4
TCM.h File .................................................................................. 66
7.5.5
TCM.cpp File............................................................................... 67
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List of Tables
Table 3-1:
Table 3-2:
Table 3-3:
Table 3-4:
Table 3-5:
Table 4-1:
Table 5-1:
Table 6-1:
Table 6-2:
Table 6-3:
Table 6-4:
Table 6-5:
Table 6-6:
Table 6-7:
Table 7-1:
Table 7-2:
Table 7-3:
Table 7-4:
Table 7-5:
Table 7-6:
Performance Specifications
I/O Characteristics
Power Requirements
Environmental Requirements
Mechanical Characteristics
TCM Pin Descriptions
Mounting Orientations
Calibration Mode Summary
12 Point North-Unaware Calibration Pattern
18 Point North-Aware Calibration Pattern
12 Point 2D Calibration Pattern
12 Point Limited Tilt Calibration Pattern
6 Point Hard Iron Only Calibration Pattern
18 Point Accelerometer Calibration Pattern
UART Configuration
Command Set
Component Identifiers
Configuration Identifiers
Sample Points
Recommended FIR Filter Tap Values
3
4
4
4
5
7
13
27
30
31
32
32
33
34
36
39
41
43
45
49
List of Figures
Figure 3-1:
Figure 3-2:
Figure 3-3:
Figure 4-1:
Figure 6-1:
Figure 6-2:
Figure 6-3:
Figure 6-4:
Figure 7-1:
TCM XB Mechanical Drawing
TCM MB Mechanical Drawing
PNI Pigtailed Cable Drawing
Mounting Orientations
Positive & Negative Roll and Pitch Definition
Full Range Calibration with 12 Point North-Unaware Cal. Pattern
Full Range Calibration with 18 Point North-Aware Cal. Pattern
Accelerometer Calibration Starting Orientations
Datagram Structure
5
6
6
9
27
29
30
34
36
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1
Copyright & Warranty Information
© Copyright PNI Sensor Corporation 2009
All Rights Reserved. Reproduction, adaptation, or translation without prior written permission is prohibited, except
as allowed under copyright laws.
Revised May 2011. For most recent version visit our website at www.pnicorp.com
PNI Sensor Corporation
133 Aviation Blvd, Suite 101
Santa Rosa, CA 95403, USA
Tel: (707) 566-2260
Fax: (707) 566-2261
Warranty and Limitation of Liability. PNI Sensor Corporation ("PNI") manufactures its TCM products (“Products”)
from parts and components that are new or equivalent to new in performance. PNI warrants that each Product to be
delivered hereunder, if properly used, will, for one year following the date of shipment unless a different warranty
time period for such Product is specified: (i) in PNI’s Price List in effect at time of order acceptance; or (ii) on PNI’s
web site (www.pnicorp.com) at time of order acceptance, be free from defects in material and workmanship and will
operate in accordance with PNI’s published specifications and documentation for the Product in effect at time of
order. PNI will make no changes to the specifications or manufacturing processes that affect form, fit, or function of
the Product without written notice to the OEM, however, PNI may at any time, without such notice, make minor
changes to specifications or manufacturing processes that do not affect the form, fit, or function of the Product. This
warranty will be void if the Products’ serial number, or other identification marks have been defaced, damaged, or
removed. This warranty does not cover wear and tear due to normal use, or damage to the Product as the result of
improper usage, neglect of care, alteration, accident, or unauthorized repair.
THE ABOVE WARRANTY IS IN LIEU OF ANY OTHER WARRANTY, WHETHER EXPRESS, IMPLIED, OR
STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY OF MERCHANTABILITY,
FITNESS FOR ANY PARTICULAR PURPOSE, OR ANY WARRANTY OTHERWISE ARISING OUT OF ANY
PROPOSAL, SPECIFICATION, OR SAMPLE. PNI NEITHER ASSUMES NOR AUTHORIZES ANY PERSON
TO ASSUME FOR IT ANY OTHER LIABILITY.
If any Product furnished hereunder fails to conform to the above warranty, OEM’s sole and exclusive remedy and
PNI’s sole and exclusive liability will be, at PNI’s option, to repair, replace, or credit OEM’s account with an
amount equal to the price paid for any such Product which fails during the applicable warranty period provided that
(i) OEM promptly notifies PNI in writing that such Product is defective and furnishes an explanation of the
deficiency; (ii) such Product is returned to PNI’s service facility at OEM’s risk and expense; and (iii) PNI is satisfied
that claimed deficiencies exist and were not caused by accident, misuse, neglect, alteration, repair, improper
installation, or improper testing. If a Product is defective, transportation charges for the return of the Product to
OEM within the United States and Canada will be paid by PNI. For all other locations, the warranty excludes all
costs of shipping, customs clearance, and other related charges. PNI will have a reasonable time to make repairs or
to replace the Product or to credit OEM’s account. PNI warrants any such repaired or replacement Product to be
free from defects in material and workmanship on the same terms as the Product originally purchased.
Except for the breach of warranty remedies set forth herein, or for personal injury, PNI shall have no liability for any
indirect or speculative damages (including, but not limited to, consequential, incidental, punitive and special
damages) relating to the use of or inability to use this Product, whether arising out of contract, negligence, tort, or
under any warranty theory, or for infringement of any other party’s intellectual property rights, irrespective of
whether PNI had advance notice of the possibility of any such damages, including, but not limited to, loss of use,
revenue or profit. In no event shall PNI’s total liability for all claims regarding a Product exceed the price paid for
the Product. PNI neither assumes nor authorizes any person to assume for it any other liabilities.
Some states and provinces do not allow limitations on how long an implied warranty lasts or the exclusion or
limitation of incidental or consequential damages, so the above limitations or exclusions may not apply to you. This
warranty gives you specific legal rights and you may have other rights that vary by state or province.
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2
Introduction
Thank you for purchasing PNI Sensor Corporation’s FieldForce TCM XB (pn 12810) or
FieldForce TCM MB (pn 13095) tilt-compensated 3-axis digital compass. The TCM is a highperformance, low-power consumption, tilt-compensated electronic compass module that
incorporates PNI’s advanced magnetic distortion compensation and calibration scoring
algorithms to provide industry-leading heading accuracy. The TCM combines PNI’s patented
magneto-inductive sensors and measurement circuit technology with a 3-axis MEMS
accelerometer for unparalleled cost effectiveness and performance.
PNI recognizes not all applications allow for significant tilt during calibration, so multiple
calibration methods are available to ensure optimized performance can be obtained in the real
world. These include Full Range Calibration, when ≥45° of tilt is possible during calibration, 2D
Calibration when constrained to calibration in a horizontal or near-horizontal plane, and Limited
Tilt Calibration when tilt is constrained to <45° but >5° of tilt is possible.
PNI also recognizes conditions may change over time, and to maintain superior heading accuracy
it may be necessary to recalibrate the compass. So the TCM incorporates Hard Iron Only
Calibration to easily account for gradual changes in the local magnetic distorting components.
And the accelerometers can be recalibrated in the field if desired.
These advantages make PNI’s TCM the choice for applications that require the highest accuracy
and performance anywhere in the world under a wide range of conditions. Applications for the
TCM include:




Unmanned vehicles – underwater (UUV), ground (UGV), & aerial (UAV)
Far target locaters and laser range finders
Dead reckoning systems
Systems in which the tilt angles used for calibration are physically constrained
With its many applications, the TCM incorporates a flexible and adaptable command set. Many
parameters are user-programmable, including reporting units, a wide range of sampling
configurations, output damping, and more.
We’re sure the TCM will help you to achieve the greatest performance from your system. Thank
you for selecting the TCM.
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3
Specifications
3.1
Performance Specifications
Table 3-1: Performance Specifications1
Parameter
Value
Accuracy
Heading
<0.3° rms
≤80° of tilt after full range calibration
<0.5° rms
≤5° of tilt after 2D calibration
<2.0° rms
≤2 times the calibration tilt angle
when using limited-tilt calibration2
<2.0° rms
Resolution
0.1°
Repeatability
0.05° rms
Range
Tilt
(Pitch & Roll)
≤65° of tilt after full range calibration
Accuracy
Pitch
± 90°
Roll
± 180°
Pitch
0.2° rms
Roll
≤65° of pitch
0.2° rms
≤80° of pitch
0.4° rms
≤86° of pitch
1.0° rms
Resolution
0.01°
Repeatability
Maximum Operational Dip Angle
Magnetometers
0.05° rms
3
85°
Calibrated Field Range
± 125 µT
Resolution
0.05 µT
Repeatability
± 0.1 µT
Footnotes:
1. Specifications are subject to change. Assumes the TCM is motionless and the local magnetic
field is clean relative to the calibration.
2. For example, if the calibration was performed over ±10° of tilt, then the TCM would provide <2°
rms accuracy over ±20° of tilt.
3. Performance at maximum operational dip angle will be somewhat degraded.
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3.2
Operating Characteristics
Table 3-2: I/O Characteristics
Parameter
Value
TCM XB
Communication
Interface
TCM MB
Communication Rate
Maximum Sample Rate1
Initial power up
Time to Initial
2
Good Data
Sleep mode recovery
Binary RS232 UART
Binary CMOS/TTL UART
300 to 115200 baud
≈30 samples/sec
<210 ms
<80 ms
Footnotes:
1. The maximum sample rate is dependent on the strength of the magnetic
field, and typically will be from 25 to 32 samples/sec.
2. FIR taps set to “0”.
Table 3-3: Power Requirements
Parameter
Supply Voltage
Value
TCM XB
TCM MB
@ max. sample rate
@ 8 Hz sample rate
Average Current Draw
@ max. sample rate
TCM MB
@ 8 Hz sample rate
During application of external
power
Peak Current Draw
During logical power up/down or
Sync Trigger
Sleep Mode Current Draw
TCM XB
3.6 to 5 VDC (unregulated)
3.3 to 5 VDC (unregulated)
20 mA typical
16 mA typical
17 mA typical
13 mA typical
120 mA pk, 60 mA avg
over 2 ms
100 mA pk, 60 mA avg
over 4 ms
0.3 mA typical
Table 3-4: Environmental Requirements
Parameter
Operating Temperature
Storage Temperature
Value
1
-40C to +85C
-40C to +85C
Footnote:
1. To meet performance specifications, recalibration may be
necessary as temperature varies.
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Table 3-5: Mechanical Characteristics
Parameter
Dimensions
(l x w x h)
Weight
Connector
Mounting Options
3.3
Value
TCM XB
TCM MB
TCM XB
TCM MB
TCM XB
TCM MB
3.5 x 4.3 x 1.3 cm
3.3 x 3.1 x 1.3 cm
6.8 gm
5.3 gm
9-pin Molex, pn 53780-0970
4-pin MIL-MAX, pn 850-10-004-10-001000
Screw mounts/standoffs, horizontal or vertical
Mechanical Drawing
The default orientation for the TCM is for the silk-screened arrow to point in the “forward” direction.
Figure 3-1: TCM XB Mechanical Drawing
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The default orientation for the TCM is for the silk-screened arrow to point in the “forward” direction.
Figure 3-2: TCM MB Mechanical Drawing
Figure 3-3: PNI Pigtailed Cable Drawing
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4
Set-Up
This section describes how to configure the TCM in your host system. To install the TCM into
your system, follow these steps:





Make electrical connections to the TCM
Evaluate the TCM using TCM Studio (TCM XB only) or a terminal emulation program,
such as HyperTerminal, to ensure the compass generally works correctly
Choose a mounting location
Mechanically mount the TCM in the host system
Perform a field calibration
4.1
Electrical Connections
The TCM XB incorporates a 9 pin Molex connector, part number 53780-0970, which mates
with Molex part 51146-0900 or equivalent. The TCM MB incorporates a 4 pin Mil-Max
connector, part number 850-10-004-10-001000, which mates with Mill-Max part 851-XX004-10-001000 or equivalent. The pin-out is given below in Table 4-1.
Table 4-1: TCM Pin Descriptions
Pin
Number1
1
2
3
4
5
6
7
8
9
TCM XB
TCM MB
9 Pin
Connector
Pigtailed Cable
Wire Color
4 Pin
Connector*
GND
GND
GND
NC
NC
NC
UART Tx
UART Rx
+5 VDC
Black
Gray
Green
Orange
Violet
Brown
Yellow
Blue
Red
GND
+5 VDC
UART Tx
UART Rx
Footnote:
1. For the TCM XB, pin #1 is indicated on Figure 3-1. For the TCM MB, pin #1
is the pin closest to the corner.
After making the electrical connections, it is a good idea to perform some simple tests to
ensure the TCM is working as expected. See Section 5 for how to operate the TCM XB with
TCM Studio or Section 7 for how to operate the TCM XB or TCM MB via the UART and
PNI binary protocol.
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4.2
Installation Location
The TCM’s wide dynamic range and sophisticated calibration algorithms allow it to operate
in many environments. For optimal performance however, you should mount the TCM with
the following considerations in mind:
4.2.1
Operate within sensors’ linear regime
The TCM can be field calibrated to correct for large static magnetic fields created by the
host system. However, each axis of the TCM has a maximum calibrated dynamic range
of ±125 µT: if the total field exceeds this value for any axis, the TCM may not give
accurate heading information. When mounting the TCM, consider the effect of any
sources of magnetic fields in the host environment that, when added to the earth’s field,
may take the sensors out of their linear regime. For example, large masses of ferrous
metals such as transformers and vehicle chassis, large electric currents, permanent
magnets such as electric motors, and so on.
4.2.2
Locate away from changing magnetic fields
It is not possible to calibrate for changing magnetic anomalies. Thus, for greatest
accuracy, keep the TCM away from sources of local magnetic distortion that will change
with time; such as electrical equipment that will be turned on and off, or ferrous bodies
that will move. Make sure the TCM is not mounted close to cargo or payload areas that
may be loaded with large sources of local magnetic fields.
4.2.3
Mount in a physically stable location
Choose a location that is isolated from excessive shock, oscillation, and vibration. The
TCM works best when stationary. Any non-gravitational acceleration results in a
distorted reading of Earth’s gravitational vector, which affects the heading measurement.
4.2.4
Location-verification testing
Location-verification testing should be performed at an early stage of development to
understand and accommodate the magnetic distortion contributors in a host system.
Determine the distance range of field distortion.
Place the compass in a fixed position, then move or energize suspect components
while observing the output to determine when they are an influence.
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Determine if the maximum field is within the linear range of the compass.
With the compass mounted, rotate and tilt the system in as many positions as
possible. While doing so, monitor the magnetometer outputs, observing if the
maximum linear range is exceeded.
4.3
Mechanical Mounting
Refer to Section 3.3 for dimensions, hole locations, and the reference frame orientation.
The TCM is factory calibrated with respect to its mounting holes. It must be aligned within
the host system with respect to these mounting holes. Ensure any stand-offs or screws used
to mount the module are non-magnetic.
The TCM can be mounted in various orientations, as shown in Figure 4-1. All reference
points are based on the white silk-screened arrow on the top side of the board. The
orientation should be programmed in the TCM using the kSetConfig command and the
kMountingRef setting, as described in Section 7.4.5
Note that the Z axis sensor and Molex connector are on the top surface of the module.
Figure 4-1: Mounting Orientations
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5
Operation with TCM Studio
The TCM Studio evaluation software communicates with the TCM XB through the RS232 serial
port of a computer. The TCM MB is not compatible with TCM Studio because it is not
compatible with an RS232-protocol serial port.
TCM Studio puts an easy-to-use, graphical-user interface (GUI) onto the binary command
language used by the TCM. Instead of manually issuing command codes, the user can use
buttons, check boxes, and dialog boxes to control the TCM and obtain data. It reads the binary
responses of the TCM output and formats this into labeled and easy-to-read data fields. TCM
Studio also includes the ability to log and save the outputs of the TCM to a file. All of this
allows you to begin understanding the capabilities of the TCM while using the TCM Studio
program’s friendly interface. Anything that can be performed using TCM Studio can also be
performed using the RS232 interface and associated protocol. Check the PNI website for the
latest TCM Studio updates at www.pnicorp.com.
Note: TCM Studio version 3.X is compatible with the TCM XB and the legacy TCM 6, but not other legacy
TCM models. Conversely, legacy TCM Studio programs will not function properly with the TCM XB. The
TCM XB model is the current RS232-version TCM with PNI’s binary communication protocol. The version
number of TCM Studio is identified in the upper left corner of the GUI.
5.1
Installation onto a Windows or Mac System
TCM Studio is provided as an executable program which can be downloaded from PNI’s
website. It will work with Windows XP, Windows Vista, Windows 7, and Mac OS X
operating systems. Check the PNI web page at www.pnicorp.com for the latest version.
For Windows computers, copy the TCMStudio.msi file onto your computer. Then, open the
file and step through the Setup Wizard.
For Mac computers, copy the TCMStudio.zip file onto your computer. This automatically
places the application in the working directory of your computer. The Quesa plug-in, also in
the .zip file, needs to be moved to /Library/CFMSupport, if it is not already there.
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5.2
Connection Tab
5.2.1
Initial Connection
If using the PNI dual-connectorized cable, ensure the batteries are well-charged.



Select the serial port the module is plugged into, which is generally COM 1.
Select 38400 as the baud rate.
Click the <Connect> button if the connection is not automatic.
Once a connection is made the “Connected” light will turn green and the module’s
firmware version, serial number, and PCA version will be displayed in the upper left next
to the PNI logo.
5.2.2
Changing Baud Rate
To change the baud rate:




In the Module window, select the new baud rate for the module.
Click the <Power Down> button. The button will change to read <Power Up>.
In the Computer window, select same baud rate for the computer.
Click the <Power Up> button. The button will revert back to <Power Down>.
Note: While it is possible to select a baud rate of 230400, the serial port will not operate this fast.
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5.2.3
Changing Modules
Once a connection has been made, TCM Studio will recall the last settings. If a different
module is used, click the <Connect> button once the new module is attached. This will
reestablish a connection, assuming the module baud rate is unchanged.
5.3
Configuration Tab
Note: No settings will be changed in the module until the <SAVE> button has been selected.
5.3.1
Mounting Options
TCM Studio supports 16 mounting orientations, as illustrated previously in Figure 4-1.
The descriptions in TCM Studio are slightly different from those shown in Figure 4-1,
and the relationship between the two sets of descriptions is given below.
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Table 5-1: Mounting Orientations
TCM Studio
Description
Figure 4-1
Description
TCM Studio
Description
Figure 4-1
Description
Standard
Standard 90
Degrees
Standard 180
Degrees
Standard 270
Degrees
X Sensor Up
X Sensor Up Plus
90 Degrees
X Sensor Up Plus
180 Degrees
X Sensor Up Plus
270 Degrees
STD 0°
Y Sensor Up
Y Sensor Up Plus
90 Degrees
Y Sensor Up Plus
180 Degrees
Y Sensor Up Plus
270 Degrees
Z Sensor Down
Z Sensor Down
Plus 90 Degrees
Z Sensor Down
Plus 180 Degrees
Z Sensor Up Plus
270 Degrees
“Y” Up 0°
5.3.2
STD 90°
STD 180°
STD 270°
“X” Up 0°
“X” Up 90°
“X” Up 180°
“X” Up 270°
“Y” Up 90°
“Y” Up 180°
“Y” Up 270°
“Z” Down 0°
“Z” Down 90°
“Z” Down 180°
“Z” Down 270°
North Reference
Magnetic
When the <Magnetic> button is selected, heading will be relative to magnetic north.
True
When the <True> button is selected, heading will be relative to true north. In this
case, the declination needs to be set in the “Declination” window. Refer to Section
6.3 for more information.
5.3.3
Endianess
Select either the <Big> or <Little> Endian button. The default setting is <Big>. See
Sections 7.2 and 7.3 for additional information.
5.3.4
Output
The TCM module can output heading, pitch, and roll in either degrees or mils. Click
either the <Degrees> or <Mils> button. The default is <Degrees>. (There are 6400 mils
in a circle, such that 1 degree = 17.7778 mils and 1 mil = 0.05625 degree.)
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5.3.5
Enable 3D Model
TCM Studio’s Test tab includes a live-action 3-D rendering of a helicopter. Some
computer systems may not have the graphics capability to render the 3D Model, for this
reason it may be necessary to turn off this feature.
5.3.6
Filter Setting (Taps)
The TCM incorporates a finite impulse response (FIR) filter to effectively provide a more
stable heading reading. The number of taps (or samples) represents the amount of
filtering to be performed. The user should select either 0, 4, 8, 16, or 32 taps, with zero
taps representing no filtering. Note that selecting a larger number of taps can
significantly slow the time for the initial sample reading and, if “Flush Filters” is
selected, the rate at which data is output. The default setting is 32.
5.3.7
Acquisition Settings
Mode
“Poll” mode should be selected when the host system will poll the TCM for data.
TCM Studio allows the user to simulate this on their PC. In this case, TCM Studio
requests data from the TCM module at a relatively fixed basis.
“Push” mode should be selected if the user will have the TCM output data at a
relatively fixed rate to the host system. In this case the TCM module is pushing data
out to TCM Studio at a relatively fixed rate.
Poll Delay
The Poll Delay is relevant when Poll Mode is selected, and is the time delay, in
seconds, between the completion of TCM Studio receiving one set of sampled data
and requesting the next sample set. If the time is set to “0”, then TCM Studio
requests new data as soon as the previous request has been fulfilled. Note that the
inverse of the Poll Delay is somewhat greater than the sample rate, since the Poll
Delay does not include actual acquisition time.
Interval Delay
The Interval Delay is relevant when Push Mode is selected, and is the time delay, in
seconds, between completion of the TCM module sending one set of sampled data
and the start of sending the next sample set. If the time is set to 0 then the TCM will
begin sending new data as soon as the previous data set has been sent. Note that the
inverse of the Interval Delay is somewhat greater than the sample rate, since the
Interval Delay does not include actual acquisition time.
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Acquire Delay
The Acquire Delay sets the time between samples taken by the module, in seconds.
This is an internal setting that is NOT tied to the time with which the module
transmits data to TCM Studio or the host system. Generally speaking, the Acquire
Delay is either set to 0, in which case the TCM is constantly sampling or set to equal
either the Poll Delay or Interval Delay values. The advantage of running with an
Acquire Delay of 0 is that the FIR filter can run with a relatively high Tap value to
provide stable and timely data. The advantage of using a greater Acquire Delay is
that power consumption can be reduced, assuming the Interval or Poll Delay are no
less than the Acquire Delay.
Flush Filters
The filtering is set to only update the filter with the last sample taken, for example
once the initial 32 samples are taken (assuming Taps is set to the default value of 32)
any new sample is added to the end with the first sample being dropped. In the case
where the “Acquire Time” is set to a value it would be prudent to set the module to
flush the filter prior to calculating the heading. This flushing will require the module
to take 32 new samples to use for the calculation.
Note: If the “Flush Filters” checkbox is checked, it will take longer for the module to output
updated data.
5.3.8
HPR During Calibration
When the <On> button is selected, heading, pitch, and roll will be output on the
Calibration tab during a calibration.
5.3.9
Calibration Settings
Automatic Sampling
When selected the module will take a sample point once minimum change and
stability requirements have been satisfied. If the user wants to have more control
over when the point will be taken then Auto Sampling should be deselected. Once
deselected, the <Take Sample> button on the Calibration tab will be active. Selecting
the <Take Sample> button will indicate to the module to take a sample once the
minimum requirements are met.
Calibration Points
The user can select the number of points to take during a calibration. The minimum
number of points needed for an initial calibration is 10, although a hard-iron only
(re)calibration can be performed with only 4 samples. The module will need to be
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rotated through at least 180 degrees in the horizontal plane with a minimum of at least
1 positive and 1 negative Pitch and at least 1 positive and 1 negative Roll as part of
the 12 points.
Calibration Method Buttons
Full Range Calibration - recommended calibration method when >45° of tilt is
possible. The minimum recommended number of calibration points is 12.
Hard Iron Only Calibration - serves as a hard iron recalibration to a prior
calibration. If the hard iron distortion around the module has changed, this
calibration can bring the module back into specification.
The minimum
recommended number of calibration points is 6.
Limited Tilt Range Calibration - recommended calibration method when >5° of tilt
calibration is available, but tilt is restricted to <45°. (i.e. full range calibration is not
possible.) The minimum recommended number of calibration points is 12.
2D Calibration - recommended when the available tilt range is limited to ≤5°. The
minimum recommended number of calibration points is 12.
Accel Calibration Only – The user should select this when accelerometer calibration
will be performed. The minimum recommended number of calibration points is 18.
Accel Calibration w/Mag – The user should select this when magnetometer and
accelerometer calibration will be performed simultaneously. The minimum
recommended number of calibration points is 18.
5.3.10
Default
Clicking this button reverts TCM Studio program to the factory default settings.
5.3.11
Retrieve
Clicking on this button causes TCM Studio to read the settings from the module and
display them on the screen.
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5.4
Calibration Tab
Note: The default settings of the module are recommended for the highest accuracy and quality of
calibration.
5.4.1
Samples
Before proceeding, refer to Section 6.2 for the recommended calibration procedure
corresponding to the calibration method selected on the Configuration tab.
Clicking the <Start> button begins the calibration process.
If “Automatic Sampling” is not checked on the Configuration tab, it is necessary to click
the <Take Sample> button to take a calibration sample point. This should be repeated
until the total number of samples (as set on the Configuration tab) is taken, changing the
orientation of the module between samples as discussed in Section 6.2.
If “Automatic Sampling” is checked, the module will need to be held steady for a short
time and then a sample automatically will be taken. Once the window indicates the next
number, the module’s orientation should be changed and held steady for the next sample.
Once the pre-set number of samples has been taken (as set on the Configuration tab) the
calibration is complete.
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5.4.2
Calibration Results
Once the calibration is complete the “Calibration Results” window will indicate the
quality of the calibration. This may take a few seconds. The primary purpose of these
scores is to demonstrate that the field calibration was successful, as demonstrated by a
low CalScore. The other parameters provide information that may assist in improving the
CalScore should it be unacceptably high.
Mag CalScore
Represents the over-riding indicator of the quality of the magnetometer calibration.
Acceptable scores will be <1 for Full Range Calibration, <2 for other methods. Note
that it is possible to get acceptable scores for Dist Error and Tilt Error and still have a
rather high Mag CalScore value. The most likely reason for this is the TCM is close
to a source of local magnetic distortion that is not fixed with respect to the module.
Dist Error
Indicates the quality of the sample point distribution, primarily looking for an even
yaw distribution. Significant clumping or a lack of sample points in a particular
section can result in a poor score. The score should be <1 and close to 0.
Tilt Error
Indicates the contribution to the CalScore caused by tilt or lack thereof, and takes into
account the calibration method. The score should be <1 and close to 0.
Tilt Range
This reports the larger of either half the full pitch range or half the full roll range of
sample points. For example, if the module is pitched +10° to -20º, and rolled +25º to
-15º, the Tilt Range value would be 20º (as derived from [+25º - {-15º}]/2). For Full
Range Calibration and Hard Iron Only Calibration, this should be ≥45°. For 2D
Calibration, this ideally should be ≈2°. For Limited Tilt Range Calibration the value
should be as large a possible given the user’s constraints.
Accel CalScore
Represents the over-riding indicator of the quality of the accelerometer calibration.
Acceptable scores will be <1.
If either CalScore is too high, click the <Start> button to begin a new calibration. If the
calibration is acceptable, then click the <Save> button in the “Calibration Results”
window to save the calibration to the module’s flash. If this button is not selected then
the module will need to be recalibrated after a power cycle.
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Note: If a calibration is aborted, all the score’s will read “179.80”, and the calibration coefficients
will not be changed. (Clicking the <Save> button will not change the calibration coefficients.)
5.4.3
Current Configuration
These indicators mimic the pertinent selections made on the Configuration tab.
5.4.4
Options
This window indicates how many samples are to be taken and provides real time heading,
pitch, and roll information if “HPR During Calibration” is set to <On>, both as defined
on the Configuration tab.
Audible Feedback
If selected TCM Studio will give an audible signal once a calibration point has been
taken. Note that an audible signal also will occur when the <Start> button is clicked,
but no data will be taken.
5.4.5
Clear
Clear Mag Cal to Factory
This button clears the user’s calibration of the magnetometers. Once selected, the
module reverts to its factory magnetometer calibration. To save this action in
nonvolatile memory, click the <Save> button. It is not necessary to clear the current
calibration in order to perform a new calibration.
Clear Accel Cal to Factory
This button clears the user’s calibration of the accelerometers. Once selected, the
module reverts back to its factory accelerometer calibration. To save this action in
non-volatile memory, click the <Save> button. It is not necessary to clear the current
calibration in order to perform a new calibration.
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5.5
Test Tab
5.5.1
Current Reading
Once the <Go> button is selected the module will begin outputting heading, pitch and roll
information. Selecting the <Stop> button or changing tabs will halt the output of the
module.
Contrast
Selecting this box sets the “Current Readings” window to have yellow lettering on a
black background, rather than black lettering on a white background.
5.5.2
3D Model
The helicopter will follow the movement of the TCM and give a visual representation of
the module’s orientation, assuming the “Enable 3D Model Display” box is selected on the
Configuration tab.
5.5.3
Acquisition Settings
These indicators mimic the pertinent selections made on the Configuration tab.
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5.5.4
Sync Mode
Sync Mode enables the module to stay in sleep mode until the user’s system sends a
trigger to report data. When so triggered, the TCM will wake up, report data once, then
return to sleep mode. One application of this is to lower power consumption. Another
use of the Sync Mode is to trigger a reading during an interval when local magnetic
sources are well understood. For instance, if a system has considerable magnetic noise
due to nearby motors, the Synch Mode can be used to take measurements when the
motors are turned off.
Enter Sync Mode
On the Test tab, above the tabs and 3D model, click the “Sync Mode” check box to
enter Sync Mode.
Sync Mode Output
To retrieve the first reading, click the <Sync Read> button. Heading, pitch and roll
information will be displayed on Current Reading window. If the “Enable 3D Model
Display” box is selected on the Configuration tab, then the helicopter will follow the
movement as well. The module will enter sleep mode after outputting the heading,
pitch, and roll information. To obtain subsequent readings, the user should first click
on the <Sync Trigger> button to wake up the module and then click on the <Sync
Read> button to get the readings, after which the module will return to sleep.
Exit Sync Mode
Click on the <Sync Trigger> button and then uncheck the “Sync Mode” check box to
exit Sync Mode.
Note that <Sync Trigger> sends a 0xFF signal as an external interrupt to wake up the
module. This is not done for the first reading as the module is already awake.
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5.6
Data Logger Tab
TCM Studio can capture measurement data and then export it to a text file. To acquire data
and export it, follow the procedure below:





Select the parameters you wish to log in the “Data” window. Use Shift-Ctrl-Click
and Ctrl-Click to select multiple items. (In the screen shot above, “Heading”, “MX
(kXAligned)”, “MY (kYAligned)”, and “MZ (kZAligned)” were selected.)
Click the <Go> button to start logging. The <Go> button changes to a <Stop> button
after data logging begins.
Click the <Stop> button to stop logging data.
Click the <Export> button to save the data to a file.
Click the <Clear> button to clear the data from the window.
Note: The data logger use ticks for time reference. A tick is 1/60 second.
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5.7
System Log Tab
The System Log tab shows all communication between TCM Studio and the TCM module
since TCM Studio was opened. Closing TCM Studio will erase the system log.
Select the <Export> button, at the bottom right of the screen, to save the system log to a text
file.
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5.8
Graph Tab
The graph provides a 2-axis (X,Y) plot of the measured field strength. The graph can be
used to visually see hard and soft iron effects within the environment measured by the TCM
module as well as corrected output after a user calibration has been performed. (The screen
shot shows the MX and MY readings as the module was held horizontally and rotated
through 360º in the horizontal plane, then held in a vertical orientation and rotated 360º in the
vertical plane.)
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6
Field Calibration
The magnetic sensors and accelerometers in the TCM are calibrated at PNI’s factory. However,
this is done in a magnetically controlled environment. Consequently, sources of magnetic
distortion positioned near the TCM in the user’s system will distort Earth’s magnetic field and
should be compensated for in the host system. Examples of such sources include ferrous metals
and alloys (ex. iron, nickel, non-stainless steel, etc.), batteries, audio speakers, current-carrying
wires, and electric motors. Compensation is accomplished by calibrating the module while
mounted in the user’s system. It is expected that the sources of magnetic distortion will remain
fixed relative to the module’s position within the user’s system. By performing a field
calibration, the TCM identifies the local sources of magnetic distortion and negates their effects
from the overall reading to provide an accurate compass heading.
Additionally, the TCM’s MEMS accelerometers gradually may change over time, and it may be
desirable to recalibrate the accelerometers from time-to-time. The accelerometer calibration
procedure corrects for changes in accelerometer gain and offset. Unlike the magnetometers, the
accelerometers may be calibrated outside the host system. Accelerometer calibration is more
sensitive to noise or hand jitter than magnetometer calibration, especially for subsequent use at
high tilt angles. Because of this, a stabilized fixture is recommended for accelerometer
calibration, although resting the unit against a stable surface often is sufficient. Alternatively,
the TCM can be returned to PNI for accelerometer recalibration.
Key Points:

Accelerometer calibration requires rotating the TCM through a full sphere of coverage.
But the TCM does need to be incorporated into the user’s system during calibration.

Magnetometer calibration requires incorporating the module into the user’s system such
that the magnetic components of the user’s system can be compensated for.

Magnetometer and accelerometer calibrations can be performed simultaneously. But it
may be easier to perform them separately since the requirements of each calibration are
significantly different. (Magnetometer calibration requires the module be incorporated in
the user’s system, while accelerometer calibration requires full sphere coverage.)

Full Range (magnetometer) Calibration provides the highest heading accuracy, but often
performing a Full Range Calibration is not practical. 2D and Limited Tilt Calibration
allow for good calibration when the range of allowable motion is limited. Hard Iron Only
Calibration relatively easily updates the hard-iron compensation coefficients.

The number of calibration sample points and the calibration pattern is dependent on the
calibration method, and these are discussed in Section 6.2.

Pay attention to the calibration scores. See Section 5.4.2 or Section 7.4.17.
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6.1
Magnetic Field Calibration Theory
The main objective of a magnetic field calibration is to compensate for distortions to the
magnetic field caused by the host system. To that end, the TCM needs to be mounted within
the host system and the entire host system needs to be moved as a single unit during the
calibration. The TCM allows the user to perform a calibration only in a 2D plane (2D
Calibration Method) or with limited tilt, but provides the greatest accuracy if the user can
rotate through a full sphere.
6.1.1
Hard and Soft Iron Effects
Hard iron distortions are caused by permanent magnets and magnetized steel or iron
objects within close proximity to the sensors. This type of distortion remains constant
and in a fixed location relative to the sensors for all heading orientations. Hard-iron
distortions add a constant magnitude field component along each axis of sensor output.
Soft-iron distortions are the result of interactions between the Earth’s magnetic field and
any magnetically “soft” material within close proximity to the sensors. In technical
terms, soft materials have a high permeability. The permeability of a given material is a
measure of how well it serves as a path for magnetic lines of force, relative to air, which
has an assigned permeability of one. Unlike hard-iron distortion, soft-iron distortion
changes as the host system’s orientation changes, making it more difficult to compensate.
The TCM 3-axis digital compass features both soft-iron and hard-iron correction.
6.1.2
Pitch and Roll
The TCM uses MEMS accelerometers to measure the tilt angle of the compass. This data
is output as pitch and roll data, and is also used in conjunction with the magnetometers to
provide a tilt-compensated heading reading.
The TCM utilizes Euler angles as the method for determining accurate orientation. This
method is the same used in aircraft orientation where the outputs are Heading (Yaw),
Pitch and Roll. When using Euler angles, roll is defined as the angle rotated around an
axis through the center of the fuselage while pitch is rotation around an axis through the
center of the wings. These two rotations are independent of each other since the rotation
axes rotate with the plane body.
For the TCM a positive pitch is when the front edge of the board is rotated upward and a
positive roll is when the right edge of the board is rotated downward.
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Figure 6-1: Positive & Negative Roll and Pitch Definition
6.2
Field Calibration Procedures
Below are instructions for performing both magnetic and accelerometer field calibrations of
the TCM module. Calibration of the TCM XB may be performed using TCM Studio or
using the PNI binary protocol, while the calibration of the TCM MB must be performed
using the PNI binary protocol. The calibration sequences described in the following sections
demonstrate a good distribution of the recommended minimum sample points. Note that
during calibration it is recommended that the location of the module remains fairly constant
while the orientation is changed.
Table 6-1: Calibration Mode Summary
Calibration
Mode
Sensors
Calibrated
Accuracy
Tilt Range during
Calibration
Number of
Samples
Full Range
2D Calibration
Limited Tilt Range
Hard Iron Only
Accelerometer
Only
Magnetic Sensors
Magnetic Sensors
Magnetic Sensors
Magnetic Sensors
0.3° rms
<2°
<2° over 2x tilt range
Restores prior accuracy
>±45°
<±5°
±5° to ±45°
>±3°
10 to 32
10 to 32
10 to 32
4 to 32
Accelerometers
Restores prior accuracy
±180°
12 to 32
Magnetic Sensors
& Accelerometers
0.3° rms
±180°
12 to 32
Accel and Mag
Before proceeding with a calibration, ensure the TCM module is properly installed in the
host system. The module should be properly installed, as discussed in Section 4, and the
software should be properly configured with respect to the mounting orientation, Endianness,
magnetic vs. true north, etc.
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Sections 5.3 and 5.4 outline how to perform a calibration using TCM Studio. To perform a
calibration using the PNI binary protocol, follow the steps listed below. Refer to Section 7
for information on how to implement the commands listed.

Using the kSetParam command, set the number of tap filters to 32.

Using the kSetConfig command, set kUserCalAutoSampling. “False” is generally
recommended, but “True” may be more convenient.

Using the kSetConfig command, set kCoeffCopySet (magnetometer calibration)
and/or kAccelCoeffCopySet (accelerometer calibration). These fields allow the user
to save multiple sets of calibration coefficients. “0” is the default.

Using the kSetConfig command again, set kUserCalNumPoints to the appropriate
number of calibration points. The number of calibration points should be at least 12
for Full Range Calibration, Limited Tilt Range Calibration and 2D Calibration; at
least 6 for Hard Iron Only Calibration; and at least 18 for Accel Only Calibration and
Accel and Mag Calibration.

Initiate a calibration using the kStartCal command. Note that this command requires
indentifying the type of calibration procedure (i.e. Full Range, 2D, etc.).

Follow the appropriate calibration procedure discussed in Sections 6.2.1 to 6.2.6. If
kUserCalAutoSampling was set to “False”, then send a kTakeUserCalSample
command when ready to take a calibration point. If kUserCalAutoSampling was set
to “True”, then look for kUserCalSampCount to confirm when a calibration point has
been taken. During the calibration process, heading, pitch, and roll information will
be output from the module, and this can be monitored using kDataResp.

When the final calibration point is taken, the module will present the calibration score
using kUserCalScore.

If the calibration is acceptable (see Section 7.4.17), save the calibration coefficients
using kSave.
6.2.1
Full Range Calibration
This calibration method is appropriate when the module can be tilted ±45° or more. The
Full Range Calibration option calibrates out hard and soft iron effects in three
dimensions, and allows for the highest accuracy readings. Two calibration patterns are
discussed below.
The 12 Point North-Unaware Calibration Pattern is a series of 3 circles of evenly spaced
points, with as much tilt variation as expected during use. This calibration pattern does
not require knowing which direction the module is facing nor does it require turning the
module upside down. The 18 Point North-Aware Calibration Pattern can provide
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superior results, especially at high dip angles (associated with high latitudes), but is more
complicated and requires: 1) knowing the direction of north prior to calibration,
2) turning the module upside down, and 3) 18 calibration points.
12 Point North-Unaware Calibration Pattern
Move the module to the following positions noting that these are not absolute heading
directions but rather relative heading changes referenced to your first heading sample.
You do not need to know actual true or magnetic north. While Figure 6-2 shows the
location of the module changing, this is for illustration purposes and it is best for the
location of the module to remain fairly constant while only the orientation is changed.
Figure 6-2: Full Range Calibration with 12 Point North-Unaware Cal. Pattern
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Table 6-2: 12 Point North-Unaware Calibration Pattern
Sample #
Yaw
Pitch
Roll
0°
90°
180°
270°
±5°
±5°
±5°
±5°
30° to 40°
-30° to -40°
30° to 40°
-30° to -40°
30°
120°
210°
300°
> +45°
> +45°
> +45°
> +45°
30° to 40°
-30° to -40°
30° to 40°
-30° to -40°
60°
150°
240°
330°
< -45°
< -45°
< -45°
< -45°
30° to 40°
-30° to -40°
30° to 40°
-30° to -40°
First Circle
1
2
3
4
Second Circle
5
6
7
8
Third Circle
9
10
11
12
18 Point North-Aware Calibration Pattern
The pattern consists of three rotations of the module, with 6 calibration points taken
for each rotation. The first rotation starts with the module horizontal and pointing
north, then rotating about the module’s y axis. The second rotation starts with the
module horizontal and pointing east, then rotating about the module’s x axis. The
third rotation starts with the module vertical and pointing north, then rotating about
the module’s z axis.
Figure 6-3: Full Range Calibration with 18 Point North-Aware Cal. Pattern
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Table 6-3: 18 Point North-Aware Calibration Pattern
Sample #
Heading
Pitch
Roll
0°
0°
180°
180°
180°
0°
0°
-60°
-60°
0°
60°
60°
0°
0°
180°
180°
180°
0°
90°
90°
90°
90°
90°
90°
0°
0°
0°
0°
0°
0°
0°
60°
120°
180°
-120°
-60°
0°
0°
180°
180°
180°
0°
0°
-60°
-60°
0°
60°
60°
-90°
-90°
90°
90°
90°
-90°
First Rotation
1
2
3
4
5
6
Second Rotation
7
8
9
10
11
12
Third Rotation
13
14
15
16
17
18
6.2.2
2D Calibration
This calibration procedure is used for very low tilt operation (< 5°) where calibrating the
module with greater tilt is not practical.
The 2D Calibration procedure calibrates for hard and soft iron effects in only two
dimensions, and in general is effective for operation and calibration in the tilt range of -5°
to +5°. The recommended calibration pattern is a circle of evenly spaced points. Results
will be optimized if the tilt in the calibration procedure can match the actual tilt
experienced when in service. For example, if the TCM will be restrained to a level plane
in service, best results are obtained if calibration is exclusively in a plane, where
“maximum…tilt” below would be 0°. PNI recommends 12 to 32 calibration points for
2D Calibration, although 10 points are acceptable but less likely to yield good results.
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Table 6-4: 12 Point 2D Calibration Pattern
6.2.3
Sample #
Yaw
Pitch
Roll
1
2
3
4
5
6
7
8
9
10
11
12
0°
30°
60°
90°
120°
150°
180°
210°
240°
270°
300°
330°
0°
max. negative
0°
max. positive
0°
max. negative
0°
max. positive
0°
max. negative
0°
max. positive
0°
max. negative
0°
max. positive
0°
max. negative
0°
max. positive
0°
max. negative
0°
max. positive
Limited Tilt Range Calibration
This procedure is recommended when 45° of tilt isn’t feasible, but >5° of tilt is possible.
It provides both hard iron and soft iron distortion correction. The recommended
calibration pattern is a series of 3 circles of evenly spaced points, with as much tilt
variation as expected during use. PNI recommends 12 to 32 calibration points for a
Limited Tilt Range Calibration, although 10 calibration points is acceptable but less
likely to yield good results.
Table 6-5: 12 Point Limited Tilt Calibration Pattern
Sample #
First Circle
1
2
3
6
Second Circle
7
8
11
12
Third Circle
13
14
17
18
Yaw
Pitch
Roll
0°
90°
180°
270°
0°
0°
0°
0°
0°
0°
0°
0°
45°
135°
225°
315°
> +5°
> +5°
> +5°
> +5°
> +5°
> +5°
> +5°
> +5°
45°
135°
225°
315°
< -5°
< -5°
< -5°
< -5°
< -5°
< -5°
< -5°
< -5°
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Note that a similar and acceptable alternative pattern would be to follow the
recommended 12 point North-Unaware Full Range Calibration pattern, but substituting
the >±45° of pitch with whatever pitch can be achieved and the ±10° to ±20° or roll with
whatever roll can be achieved up to these limits. (See Section 6.2.1)
6.2.4
Hard Iron Only Calibration
Over time the magnetic distortions around the TCM may change for a variety of reasons.
The Hard Iron Only Calibration allows for quick recalibration of the module for hard iron
effects, and generally is effective for operation and calibration in the tilt range of 3° or
more (≥45° is preferred). The recommended calibration pattern is a circle of alternately
tilted, evenly spaced points, with as much tilt as expected during use. PNI recommends
≥6 calibration points for a Hard Iron Only Calibration, although 4 points is acceptable.
Table 6-6: 6 Point Hard Iron Only Calibration Pattern
6.2.5
Sample #
Yaw
Pitch
Roll
1
2
3
4
5
6
0°
60°
120°
180°
240°
300°
-45°
+45°
-45°
+45°
-45°
+45°
-45°
+45°
-45°
+45°
-45°
+45°
Accelerometer Only Calibration
The requirements for a good accelerometer calibration differ from the requirements for a
good magnetometer calibration. For instance, a level yaw sweep, no matter how many
points are acquired, is effectively only 1 accelerometer calibration point. PNI
recommends 18 to 32 calibration points for accelerometer calibration, although 12
calibration points is acceptable.
Figure 6-4 shows the two basic starting positions for the Accelerometer Only Calibration.
Calibration can occur within the user’s system or with the module alone. It is not
necessary to place the TCM on a hard surface as shown, but the it must be held very still
during calibration, and holding it against a hard surface is one method to help ensure this.
Starting with the module as shown on the left in Figure 6-4, rotate the module such that it
sits on each of its 6 faces. Take a calibration point on each face. Starting with the
module as shown on the right, take a calibration point with it being vertical (0°). Now tilt
the module back 45° and take another calibration point (+45°), then tilt the module
forward 45° and take another calibration point (-45°). Repeat this 3 point calibration
process for the module with it resting on each of its 4 corners.
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Figure 6-4: Accelerometer Calibration Starting Orientations
Table 6-7: 18 Point Accelerometer Calibration Pattern
Sample #
Yaw
Pitch
Roll
0°
0°
180°
0°
0°
0°
0°
90°
0°
-90°
0°
0°
90°
90°
-90°
90°
0°
180°
0°
90°
180°
±5°
±5°
±5°
10° to 20°
-10° to -20°
10° to 20°
270°
30°
120°
±5°
> +45°
> +45°
-10° to -20°
10° to 20°
-10° to -20°
210°
300°
60°
> +45°
> +45°
< -45°
10° to 20°
-10° to -20°
10° to 20°
150°
240°
330°
< -45°
< -45°
< -45°
-10° to -20°
10° to 20°
-10° to -20°
Sides
1
2
3
4
5
6
First Corner
7
8
9
Second Corner
10
11
12
Third Corner
13
14
15
Fourth Corner
16
17
18
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6.2.6
Mag and Accel Calibration
The TCM allows for a simultaneous magnetometer and accelerometer calibration. This
requires a good calibration pattern, stable measurements (not handheld), and installation
in the user’s system such that the appropriate local magnetic environment is present. PNI
recommends 18 to 32 calibration points for a Mag and Accel Calibration, although 12
points is acceptable but less likely to yield good results. The Accelerometer Only
Calibration pattern discussed in Section 6.2.5 will work for a Mag and Accel Calibration.
Optimal performance is obtained when all rotations of the cube are performed towards
magnetic north to achieve the widest possible magnetic field distribution.
Note that combining calibrations only makes sense if all the host system’s magnetic
distortions (steel structures or batteries, for instance) are present and fixed relative to the
module when calibrating. If the Accelerometer Only Calibration is performed, the user’s
system distortions are not relevant, which allows the TCM to be removed from the host
system in order to perform the Accelerometer Only Calibration.
6.3
Declination Value
Declination, also called magnetic variation, is the difference between true and magnetic
north. It is measured in degrees east or west of true north. Correcting for declination is
accomplished by storing the correct declination angle, and then changing the heading
reference from magnetic north to true north. Declination angles vary throughout the world,
and change very slowly over time. For the greatest possible accuracy, go to the National
Geophysical Data Center web page below to get the declination angle based on your latitude
and longitude: http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp
6.4
Other Considerations
The TCM measures the total magnetic field within its vicinity, and this is a combination of
Earth’s magnetic field and local magnetic sources. The TCM can compensate for local static
magnetic sources. However, a magnetic source which is not static can create errors (such as
a motor which turns on/off), and it is not possible to compensate for such a dynamic nature.
In such cases, moving the TCM away from dynamic magnetic fields is recommended, or
taking measurements only when the state of the magnetic field is know (ex. only take
measurements when a nearby motor is turned off).
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7
Operation with PNI Binary Protocol
The TCM utilizes a binary protocol that is transmitted over an RS232 UART (TCM XB) or a
TTL UART (TCM MB). The parameters should be set as follows:
Table 7-1: UART Configuration
7.1
Parameter
Value
Number of Data Bits
Start Bits
Stop Bits
Parity
8
1
1
none
Datagram Structure
The data structure is shown below:
ByteCount
(UInt16)
Packet Frame
(1 - 4092 UInt8)
Frame
ID
(UInt8)
CRC-16
(UInt16)
Payload
(1 - 4091 UInt8)
Figure 7-1: Datagram Structure
The ByteCount is the total number of bytes in the packet including the CRC-16 (checksum).
CRC-16 is calculated starting from the ByteCount to the last byte of the Packet Frame. The
ByteCount and CRC-16 are always transmitted in big Endian. Two examples follow.
Example: The complete packet for the kGetModInfo command, which has no payload is:
00 05
01
EF D4
ByteCount
Frame ID
Checksum
Example: Below is a complete sample packet to start a 2D Calibration (kStartCal):
00 09
0A
00 00
00 14
5C F9
ByteCount
Frame ID
CalOption
CalOption
(2D Calibration)
Checksum
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7.2
Parameter Formats
Note: Floating-point based parameters conform to ANSI/IEEE Std 754-1985. Please refer to the
Standard for more information. PNI also recommends the user refer to the compiler’s instructions to
understand how the compiler implements floating-point format.
64 Bit Floating Point (Float64)
Below is the 64 bit float format in big Endian. In little Endian, the bytes are in
reverse order in 4 byte groups. (eg. big Endian: ABCD EFGH; little Endian:
DCBA HGFE).
63 62
S
52 51
0
Exponent
Mantissa
The value (v) is determined as (if and only if 0 < Exponent < 2047): v = (-1)S *
2(Exponent-1023) * 1.Mantissa
32 Bit Floating Point (Float32)
Shown below is the 32 bit float format in big Endian. In little Endian format, the 4
bytes are in reverse order (LSB first).
3130
S
23 22
0
Exponent
Mantissa
The value (v) is determined as (if and only if 0 < Exponent < 255): v = (-1)S *
2(Exponent-127) * 1.Mantissa
Signed 32 Bit Integer (SInt32)
SInt32-based parameters are signed 32 bit numbers (2’s compliment).
represents the sign of the value (0=positive, 1=negative)
31
24 23
16 15
8 7
msb
Bit 31
0
lsb
Big Endian
7
0 15
8 23
lsb
16 31
24
msb
Little Endian
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Signed 16 Bit Integer (SInt16)
SInt16-based parameters are signed 16 bit numbers (2’s compliment).
represents the sign of the value (0=positive, 1=negative)
15
8 7
msb
0
7
0 15
8
lsb
lsb
Bit 15
msb
Little Endian
Big Endian
Signed 8 Bit Integer (SInt8)
UInt8-based parameters are unsigned 8-bit numbers. Bit 7 represents the sign of the
value (0=positive, 1=negative)
7
0
byte
Unsigned 32 Bit Integer (UInt32)
UInt32-based parameters are unsigned 32 bit numbers.
31
24 23
16 15
8 7
msb
0
lsb
Big Endian
7
0 15
8 23
16 31
lsb
24
msb
Little Endian
Unsigned 16 Bit Integer (UInt16)
UInt16-based parameters are unsigned 16 bit numbers.
15
8 7
msb
0
lsb
7
0 15
lsb
Big Endian
8
msb
Little Endian
Unsigned 8 Bit Integer (UInt8)
UInt8-based parameters are unsigned 8-bit numbers.
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7
0
byte
Boolean
Boolean is a 1-byte parameter that MUST have the value 0 (FALSE) or 1 (TRUE).
7
0
byte
7.3
Commands & Communication Frames
Table 7-2: Command Set
Frame
Command
IDd
1
2
3
4
5
6
7
8
9
10
11
kGetModInfo
kModInfoResp
kSetDataComponents
kGetData
kDataResp
kSetConfig
kGetConfig
kConfigResp
kSave
kStartCal
kStopCal
12
kSetParam
13
kGetParam
14
kParamResp
15
16
17
18
19
20
21
22
23
24
kPowerDown
kSaveDone
kUserCalSampCount
kUserCalScore
kSetConfigDone
kSetParamDone
kStartIntervalMode
kStopIntervalMode
kPowerUp
kSetAcqParams
Description
Queries the modules type and firmware revision number.
Response to kGetModInfo
Sets the data components to be output.
Queries the module for data
Response to kGetData
Sets internal configurations in the module
Queries the module for the current internal configuration value
Response to kGetConfig
Commands the module to save internal and user calibration
Commands the module to start user calibration
Commands the module to stop user calibration
Sets the FIR filter settings for the magnetometer &
accelerometer sensors.
Queries for the FIR filter settings for the magnetometer &
accelerometer sensors.
Contains the FIR filter settings for the magnetometer &
accelerometer sensors.
Used to completely power-down the module
Response to kSave
Sent from the module after taking a calibration sample point
Contains the calibration score
Response to kSetConfig
Response to kSetParam
Commands the module to output data at a fixed interval
Commands the module to stop data output at a fixed interval
Sent after wake up from power down mode
Sets the sensor acquisition parameters
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25
26
27
28
29
30
kGetAcqParams
kAcqParamsDone
kAcqParamsResp
kPowerDownDone
kFactoryUserCal
kFactorUserCalDone
31
kTakeUserCalSample
36
37
46
47
49
kFactoryInclCal
kFactoryInclCalDone
kSetMode
kSetModeResp
kSyncRead
7.4
Queries for the sensor acquisition parameters
Response to kSetAcqParams
Response to kGetAcqParams
Response to kPowerDown
Clears user magnetometer calibration coefficients
Response to kFactoryUserCal
Commands the module to take a sample during user
calibration
Clears user accelerometer calibration coefficients
Respond to kFactoryInclCal
Sets the mode of operation of the system
Response to kSetMode
Queries the module for data in Sync Mode
kGetModInfo (frame ID 1d)
This frame queries the module's type and firmware revision number. The frame has no
payload.
7.4.1
kModInfoResp (frame ID 2d)
This frame is the response to kGetModInfo frame. The payload contains the module type
identifier followed by the firmware revision number.
Payload
Type
Revision
UInt32
UInt32
Note that the Type and Revision can be decoded from the binary format to character
format using the ASCII standard. For example, the hex string “00 0D 02 54 43 4D 35 31
32 30 38 C7 87” can be decoded to read “TCM5 1208”. Also, the TCM XB is referenced
as Type “TCM6” since the number of Type characters is limited to 4.
7.4.2
kSetDataComponents (frame ID 3d)
This frame sets the data components in the module's data output. This is not a query for
the module's data (see kGetModInfo). The first byte of the payload indicates the number
of data components followed by the data component IDs.
Payload
Count
ID1
ID2
ID3
IDCount
UInt8
UInt8
UInt8
UInt8
UInt8
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Example: To query the heading and pitch, the payload should contain
Payload
3
2
5
24
Frame ID
ID Count
Heading ID
Pitch ID
When querying for data (kGetData frame), the sequence of the data component output
follows the sequence of the data component IDs as set in this frame.
Table 7-3: Component Identifiers
Component
Component
Format
IDd
Units
Range
0.0˚ to 359.9˚
kHeading
5
Float32
kTemperature
7
Float32
degrees (default)
or mils
˚ Celsius
kDistortion
8
Boolean
True or False
kCalStatus
9
Boolean
True or False
kPAligned
KRAligned
kIZAligned
kPAngle
21
22
23
24
Float32
Float32
Float32
Float32
G
G
G
degrees
kRAngle
25
Float32
degrees
KXAligned
KYAligned
KZAligned
27
28
29
Float32
Float32
Float32
T
T
T
-40˚ to 85˚
False (Default)
= no distortion
False (Default)
= not calibrated
-1.0 to 1.0
-1.0 to 1.0
-1.0 to 1.0
-90.0˚ to 90.0˚
-180.0˚ to
180.0˚
Component types are listed below. All are read-only values.
kHeading (Component ID 5d)
Provides compass heading (i.e. yaw or azimuth) output. The units default to degrees,
but can be set to mils using kMilOutput
kTemperature (Component ID 7d)
This value is provided by the module’s internal temperature sensor. Its value is in °
Celsius and has an accuracy of ±3° C.
kDistortion (Component ID 8d)
This flag indicates at least one magnetometer axis reading is beyond ±125 µT.
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kCalStatus (Component ID 9d)
This flag indicates the user calibration status. False (default) = not calibrated.
kPAligned, kRAligned & kIZAligned (Component IDs 21d, 22d, 23d)
These values represent Earth’s calibrated acceleration vector (G) components. The
default values are the factory calibrated values. Up to three (3) sets of values can be
stored using kAccelCoeffCopySet (see Section 7.4.5), and this command references
whichever set currently is being used.
kPAngle, kRAngle (Component IDs 24d, 25d)
These outputs provide pitch and roll angles. The pitch range is -90.0˚ to +90.0˚, and
the roll range is to -180.0˚ to +180.0˚.
kXAligned, kYAligned, kZAligned (Component IDs 27d, 28d, 29d)
These values represent Earth’s calibrated magnetic field (M) vector components. The
default values are the factory-calibrated values. Note that up to eight (8) sets of
values can be stored using kCoeffCopySet (see Section 7.4.5), and this command
references whichever set currently is being used.
7.4.3
kGetData (frame ID 4d)
This frame queries the module for data, as established in kSetDataComponents. The
frame has no payload. The complete packet for the kGetData command is:
00 05
04
BF71
Where “00 05” is the byte count, “04” is the kGetData command, and “BF 71” is the
CRC-16 checksum.
7.4.4
kDataResp (frame ID 5d)
This frame is the response to the kGetData frame. The first byte of the payload indicates
the number of data components, followed by the data component ID-value pairs. The
sequence of component IDs follows the sequence set in the kSetDataComponents frame.
Payload
Count
ID1
ValueID1
ID2
ValueID2
IDCount
ValueIDCount
UInt8
UInt8
ID
Specific
UInt8
ID
Specific
UInt8
ID
Specific
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Example: If the response contains heading and pitch, the payload would look like:
2
5
359.9
24
10.5
ID Count
Heading ID
Heading
Output
(Float32)
Pitch ID
Pitch
Output
(Float32)
7.4.5
kSetConfig (frame ID 6d)
This frame sets internal configurations in the module. The first byte of the payload is the
configuration ID followed by a format-specific value. These configurations can only be
set one at time.
Payload
Config ID
Value
UInt8
ID
Specific
Example: To configure the declination, the payload would look like:
1
10.0
Declination ID
Declination
Angle
(Float32)
Table 7-4: Configuration Identifiers
Settings
Config. IDd
Format
Values / Range
Default
kDeclination
kTrueNorth
kBigEndian
1
2
6
Float32
Boolean
Boolean
0˚
False
True
kMountingRef*
10
UInt8
kUserCalNumPoints
12
UInt32
-180˚ to +180˚
True or False
True or False
1 = STD 0°
2 = X UP 0°
3 = Y UP 0°
4 = STD 90°
5 = STD 180°
6 = STD 270°
7 = Z DOWN 0°
8 = X UP 90°
9 = X UP 180°
10 = X UP 270°
11 = Y UP 90°
12 = Y UP 180°
13 = Y UP 270°
14 = Z DOWN 90°
15 = Z DOWN 180°
16 = Z DOWN 270°
4 – 32
1
12
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kUserCalAutoSampling
13
Boolean
True or False
0 – 300
1 – 600
2 – 1200
3 – 1800
4 – 2400
5 – 3600
6 – 4800
kBaudRate
14
UInt8
7 – 7200
8 – 9600
9 – 14400
10 – 19200
11 – 28800
12 – 38400
13 – 57600
14 - 115200
kMilOutput
15
Boolean
True or False
kDataCal
16
Boolean
True or False
kCoeffCopySet
18
UInt32
0-7
kAccelCoeffCopySet
19
UInt32
0-2
*Refer to Figure 4-1 for additional information on mounting orientations.
True
12
False
True
0
0
Configuration parameters and settings for kSetConfig:
kDeclination (Config. ID 1d)
This sets the declination angle to determine True North heading. Positive declination
is easterly declination and negative is westerly declination. This is not applied until
kTrueNorth is set to TRUE.
kTrueNorth (Config. ID 2d)
Flag to set compass heading output to true north heading by adding the declination
angle to the magnetic north heading.
kBigEndian (Config. ID 6d)
Sets the Endianness of packets. TRUE is Big Endian. FALSE is Little Endian.
kMountingRef (Config. ID 10d)
This sets the reference orientation for the module. Please refer to and Figure 4-1 for
additional information
kUserCalNumPoints (Config. ID 12d)
The user must select the number of points to take during a calibration. The number of
sample points must be within the listed “Allowable Range” or the module may not
work properly. Calibration generally is not as good if less than the “Minimum
Recommended” is selected, but may be acceptable. See Section 6.2 for additional
information.
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Table 7-5: Sample Points
Number of Samples
Calibration Mode
Allowable
Range
Minimum
Recommended
Full Range
2D Calibration
Limited Tilt Range
Hard Iron Only
Accelerometer Only
Accel and Mag
10 to 32
10 to 32
10 to 32
4 to 32
12 to 32
12 to 32
12
12
12
6
18
18
kUserCalAutoSampling (Config. ID 13d)
This flag is used during user calibration. If set to TRUE, the module automatically
takes calibration sample points once the minimum change requirement is met. If set
to FALSE, the module waits for kTakeUserCalSample to take a sample with the
condition that a magnetic field vector component delta is greater than 5 µT from the
last sample point. If the user wants to have maximum control over when the
calibration sample point are taken then this flag should be set to FALSE.
kBaudRate (Config. ID 14d)
Baud rate index value. A power-down power-up cycle is required when changing the
baud rate.
kMilOutput (Config. ID 15d)
This flag sets the heading, pitch and roll output to mils. By default, kMilOutput is set
to FALSE and the heading, pitch and roll output are in degrees. Note that 360
degrees = 6400 mils, such that 1 degree = 17.778 mils or 1 mil = 0.05625 degree.
kDataCal (Config. ID 16d)
This flag sets whether or not heading, pitch, and roll data are output simultaneously
while the TCM is being calibrated. The default is TRUE, such that heading, pitch,
and roll are output during calibration. FALSE disables simultaneous output.
kCoeffCopySet (Config. ID 18d)
This command provides the flexibility to store up to eight (8) sets of magnetometer
calibration coefficients in the module. The default is set number 0. To store a set of
coefficients, first establish the set number (number 0 to 7) using kCoeffCopySet, then
perform the magnetometer calibration. The coefficient values will be stored in the
defined set number. This feature is useful if the compass will be placed in multiple
locations that have different local magnetic field properties.
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kAccelCoeffCopySet (Config. ID 19d)
This command provides the flexibility to store up to three (3) sets of accelerometer
calibration coefficients in the module. The default is set number 0. To store a set of
coefficients, first establish the set number (number 0 to 2) using
kAccelCoeffCopySet, then perform the accelerometer calibration. The coefficient
values will be stored in the defined set number.
7.4.6
kGetConfig (frame ID 7d)
This frame queries the module for the current internal configuration value. The payload
contains the configuration ID requested.
Payload
Config ID
UInt8
7.4.7
kConfigResp (frame ID 8d)
This frame is the response to kGetConfig frame. The payload contains the configuration
ID and value.
Payload
Config ID
Value
UInt8
ID
Specific
Example: If a request to get the set declination angle, the payload would look like:
1
10.0
Declination ID
Declination
Angle
(Float32)
7.4.8
kSave (frame ID 9d)
This frame commands the module to save internal configurations and user calibration to
non-volatile memory. Internal configurations and user calibration is restored on power
up. The frame has no payload. This is the ONLY command that causes the module to
save information into non-volatile memory.
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7.4.9
kStartCal (frame ID 10d)
This frame commands the module to start user calibration with the current sensor
acquisition parameters, internal configurations and FIR filter settings. After sending this
command, the module ensures the stability condition is met, takes the first calibration
point, and then responds with kUserCalSampCount. kUserCalSampCount will continue
to be sent after each sample is taken. (Subsequent samples will be taken when
autosampling when the minimum change and stability conditions are met, or manually
after the kTakeUserCalSample is sent and the stability condition is met.) See Section 6.2
for more information on the various calibration procedures.
Note: The payload needs to be 32 bit (4 byte). If no payload is entered or if less than 4 bytes are
entered, the unit will default to the previous calibration method.
Payload
Cal Option
UInt32
The CalOption values are given below, along with basic descriptions of the options.
Full Range Calibration - magnetic only (10d = 0Ah)
Recommended calibration method when >45° of tilt is possible.
2D Calibration - magnetic only (20d = 14h)
Recommended when the available tilt range is limited to ≤5°.
Hard Iron Only Calibration - magnetic only (30d = 1Eh)
Recalibrates the hard iron offset for a prior calibration. If the local field hard iron
distortion has changed, this calibration can bring the module back into specification.
Limited Tilt Range Calibration – magnetic only (40d = 28h)
Recommended calibration method when >5° of tilt calibration is available, but tilt is
restricted to <45°. (i.e. full range calibration is not possible.)
Accelerometer Only Calibration (100d = 64h)
Select this when only accelerometer calibration will be performed.
Accelerometer and Magnetic Calibration (110d = 6Eh = )
Selected when magnetic and accelerometer calibration will be done simultaneously.
Below is a complete sample frame for a 2D Calibration:
00 09 0A 00 00 00 14 5C F9
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Heading, pitch and roll information a output via the kDataResp frame during the
calibration process. This feature provides guidance during the calibration regarding
calibration sample point coverage. During calibration, in the kDataResp frame, the
number of data components is set to be 3 and then followed by the data component IDvalue pairs. The sequence of the component IDs are kHeading, kPAngle and kRAngle.
7.4.10
kStopCal (frame ID 11d)
This command aborts the calibration process and is not required to generally stop a
calibration process. Assuming the minimum number of sample points for the calibration
(as defined in Table 7-5) is not acquired prior to sending kStopCal, the prior calibration
results are retained. If the acquired number of sample points prior to sending kStopCal si
within the allowable range of kUserCalNumPoints, then new calibration coefficients and
a new score will be generated. For instance, if kUserCalNumPoints is set to 32 for a full
range calibration, and kStopCal is sent after taking the 12th sample point, then a new set
of coefficients will be generated based on the 12 sample points that were taken.
7.4.11
kSetParam (frame ID 12d)
The TCM incorporates a finite impulse response (FIR) filter to provide a more stable
heading reading. The number of taps (or samples) represents the amount of filtering to be
performed. Selecting a larger number of taps can significantly slow the time for the
initial sample reading and, if “Flush Filters” is selected, the rate at which data is output.
Payload
Parameter ID
Axis ID
Count
Value1
Value2
Value3
ValueCount
UInt8
UInt8
UInt8
ID
Specific
ID
Specific
ID
Specific
ID
Specific
Parameter ID should be set to 3 and the Axis ID should be set to 1. The third payload
byte indicates the number of FIR taps to use, which can be 0 (no filtering), 4, 8, 16, or 32.
This is followed by the tap values (0 to 32 total Values can be in the payload), with each
Value being a Float64, and suggested values given in Table 7-6.
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Table 7-6: Recommended FIR Filter Tap Values
Count 4 Tap Filter
8 Tap Filter
16 Tap Filter
32 Tap Filter
1
04.6708657655334e-2
01.9875512449729e-2
07.9724971069144e-3
01.4823725958818e-3
2
04.5329134234467e-1
06.4500864832660e-2
01.2710056429342e-2
02.0737124095482e-3
3
04.5329134234467e-1
01.6637325898141e-1
02.5971390034516e-2
03.2757326624196e-3
4
04.6708657655334e-2
02.4925036373620e-1
04.6451949792704e-2
05.3097803863757e-3
5
02.4925036373620e-1
07.1024151197772e-2
08.3414139286254e-3
6
01.6637325898141e-1
09.5354386848804e-2
01.2456836057785e-2
7
06.4500864832660e-2
01.1484431942626e-1
01.7646051430536e-2
8
01.9875512449729e-2
01.2567124916369e-1
02.3794805168613e-2
9
01.2567124916369e-1
03.0686505921968e-2
10
01.1484431942626e-1
03.8014333463472e-2
11
09.5354386848804e-2
04.5402682509802e-2
12
07.1024151197772e-2
05.2436112653103e-2
13
04.6451949792704e-2
05.8693165018301e-2
14
02.5971390034516e-2
06.3781858267530e-2
15
01.2710056429342e-2
06.7373451424187e-2
16
07.9724971069144e-3
06.9231186101853e-2
17
06.9231186101853e-2
18
06.7373451424187e-2
19
06.3781858267530e-2
20
05.8693165018301e-2
21
05.2436112653103e-2
22
04.5402682509802e-2
23
03.8014333463472e-2
24
03.0686505921968e-2
25
02.3794805168613e-2
26
01.7646051430536e-2
27
01.2456836057785e-2
28
08.3414139286254e-3
29
05.3097803863757e-3
30
03.2757326624196e-3
31
02.0737124095482e-3
32
01.4823725958818e-3
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7.4.12
kGetParam (frame ID 13d)
This frame queries the FIR filter settings for the sensors. Parameter ID should be set to 3
and the Axis ID should be set to 1.
Payload
Parameter ID
Axis ID
UInt8
UInt8
7.4.13
kParamResp (frame ID 14 d)
This frame contains the current FIR filter settings. The format and values will the same
as defined by kSetParam.
Payload
Parameter ID
Axis ID
Count
Value1
Value2
Value3
ValueCount
UInt8
UInt8
UInt8
Filter Top
Value
ID
Specific
ID
Specific
ID
Specific
7.4.14
kPowerDown (frame ID 15 d)
This frame is used to completely power-down the module, which is referred to as putting
the module in Sleep Mode. The frame has no payload. The module will power down all
peripherals including the RS-232 driver but the driver chip has the feature to keep the Rx
line enabled. Any character sent to the module causes it to exit power down mode. It is
recommended to send the byte oxFFh.
7.4.15
kSaveDone (frame ID 16 d)
This frame is the response to kSave frame. The payload contains a UInt16 error code,
0000h indicates no error, 0001h indicates error when attempting to save data into nonvolatile memory.
Payload
Error code
UInt16
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7.4.16
kUserCalSampCount (frame ID 17 d)
This frame is sent from the module after taking a calibration sample point. The payload
contains the sample count with the range of 1 to 32.
Payload
Sample count
UInt32
7.4.17
kUserCalScore (frame ID 18 d)
This frame's payload contains the calibration score, which is a series of Float32 values:
CalScore, Calparam2,Calparam3,DistErr,TiltErr,TiltRange.
Payload
CalScore
Calparam2
Accel CalScore
DistErr
TiltErr
TiltRange
Float32
Float32
Float32
Float32
Float32
Float32
CalScore (Mag CalScore):
Represents the over-riding indicator of the quality of the magnetometer calibration.
Acceptable scores will be ≤1 for full range calibration, ≤2 for other methods. Note
that it is possible to get acceptable scores for DistErr and TiltErr and still have a
rather high Mag CalScore value. The most likely reason for this is the TCM is close
to a source of local magnetic distortion that is not fixed with respect to the module.
Calparam2:
Reserved values for PNI use.
Calparam3 (Accel CalScore):
Represents the over-riding indicator of the quality of the accelerometer calibration.
An acceptable score is ≤1.
DistErr:
Indicates the quality of the sample point distribution, primarily looking for an even
yaw distribution. Significant clumping or a lack of sample points in a particular
section can result in a poor score. The score should be ≤1.
TiltErr:
Indicates the contribution to the CalScore caused by tilt or lack thereof. The score
takes into account the calibration method. The score should be ≤1.
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TiltRange:
This reports the larger of either half the full pitch range or half the full roll range of
sample points. For example, if the module is pitched +10° to -20º, and rolled +25º to
-15º, the Tilt Range value would be 20º (as derived from [+25º - {-15º}]/2). For Full
Range Calibration and Hard Iron Only Calibration, this should be ≥45°. For 2D
Calibration, this ideally should be ≈2°. For Limited Tilt Range Calibration the value
should be as large a possible given the user’s constraints.
7.4.18
kSetConfigDone (frame ID 19 d)
This frame is the response to kSetConfig frame. The frame has no payload.
7.4.19
kSetParamDone (frame ID 20 d)
This frame is the response to kSetParam frame. The frame has no payload.
7.4.20
kStartIntervalMode (frame ID 21 d)
This frame commands the module to output data at a fixed time interval, otherwise
known as Push mode. See kSetAcqParams. The frame has no payload.
7.4.21
kStopIntervalMode (frame ID 22 d)
This frame commands the module to stop data output when in Push mode. The frame has
no payload.
7.4.22
kPowerUp (frame ID 23 d)
This frame is sent from the module after waking up from Sleep Mode. The frame has no
payload. Since the module was previously powered down which drives the RS-232
driver TX line low (break signal), it is recommended to disregard the first byte.
7.4.23
kSetAcqParams (frame ID 24 d)
This frame sets the sensor acquisition parameters in the module. The payload should
contain the following:
Payload
PollingMode
FlushFilter
SensorAcqTime
IntervalRespTime
UInt8
UInt8
Float32
Float32
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PollingMode:
This flag sets whether output will be presented in Poll or Push mode. Poll mode is
TRUE and is the default. Poll mode should be selected when the host system will
poll the TCM for data. Push mode should be selected if the user will have the TCM
output data at a relatively fixed rate to the host system. See kStartIntervalMode for
starting a Push Mode command.
FlushFilter:
Setting this flag to TRUE will result in the FIR filters being flushed (reset) after every
sample. The default is FALSE (no flushing).
The filtering is set to only update the filter with the last sample taken, for example
once the initial 32 samples are taken (assuming FIR Taps is set to the default value of
32) any new sample is added to the end with the first sample being dropped. In the
case where SensorAcqTime is set to a value it would be prudent to set the module to
flush the filter prior to calculating the heading. This flushing will require the module
to take 32 new samples to use for the calculation.
SensorAcqTime:
The SensorAcqTime sets the time between samples taken by the module, in seconds.
The default is 0.0 seconds, which means that the module will reacquire data
immediately after the last acquisition. This is an internal setting that is NOT tied to
the time with which the module transmits data to the host system. Generally
speaking, the SensorAcqTime is either set to 0, in which case the TCM is constantly
sampling, or set to equal the IntervalRespTime value. The advantage of running with
an SensorAcqTime of 0 is the FIR filter can run with a relatively high FIR Tap value
to provide stable and timely data. The advantage of using a greater SensorAcqTime
is power consumption can be reduced, assuming the IntervalRespTime is no less than
the SensorAcqTime.
IntervalRespTime:
The IntervalRespTime is relevant when Push Mode is selected, and is the time delay,
in seconds, between completion of the TCM module sending one set of sampled data
and the start of sending the next sample set. The default is 0.0 seconds, which means
the TCM will begin sending new data as soon as the previous data set has been sent.
Note that the inverse of the IntervalRespTime is somewhat greater than the sample
rate, since the IntervalRespTime does not include actual acquisition time
7.4.24
kGetAcqParams (frame ID 25 d)
This frame queries the unit for acquisition parameters. The frame has no payload.
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7.4.25
kAcqParamsDone (frame ID 26 d)
This frame is the response to kSetAcqParams frame. The frame has no payload.
7.4.26
kAcqParamsResp (frame ID 27 d)
This frame is the response to kGetAcqParams frame. The payload should contain the
same payload as the kSetAcqParams frame.
7.4.27
kPowerDownDone (frame ID 28 d)
This frame is the response to kPowerDown frame. This indicates that the module
successfully received the kPowerDone frame and is in the process of powering down.
The frame has no payload.
7.4.28
kFactoryUserCal (frame ID 29 d)
This frame clears the user magnetometer calibration coefficients. The frame has no
payload. This frame must be followed by the kSave frame to change in non-volatile
memory.
7.4.29
kFactoryUserCalDone (frame ID 30 d)
This frame is the response to kFactoryUserCal frame. The frame has no payload.
7.4.30
kTakeUserCalSample (frame ID 31 d)
This frame commands the module to take a sample during user calibration. The frame
has no payload.
7.4.31
kFactoryInclCal (frame ID 36 d)
This frame clears the user accelerometer calibration coefficients. The frame has no
payload. This frame must be followed by the kSave frame to change in non-volatile
memory.
7.4.32
kFactoryInclCalDone (frame ID 37 d)
This frame is the response to kFactoryInclCal frame. The frame has no payload.
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7.4.33
kSetMode (frame ID 46 d)
Note: When Sync Mode is selected, the TCM will acknowledge the change in mode and
immediately trigger the Sync Mode and send a data frame.
This frame allows the module to be placed in Sync Mode. When in Sync Mode the
module will stay in Sleep Mode until the user’s system sends a trigger to report data.
When so triggered, the TCM will wake up, report data once, then return to Sleep Mode.
One application of this is to lower power consumption. Another use of the Sync Mode is
to trigger a reading during an interval when local magnetic sources are well understood.
For instance, if a system has considerable magnetic noise due to nearby motors, the
Synch Mode can be used to take measurements when the motors are turned off.
The payload contains the Mode ID requested, as given below.
Payload
Mode ID:
Mode ID
Normal Mode = 0
Sync Mode = 100
UInt8
If the module is in Sync Mode and the user desires to switch back to Normal Mode, an
“FFh” string first must be sent, followed by some minimum delay time prior to sending
the kSetMode frame. The minimum delay time is dependent on the baud rate, and for a
baud rate equal to or slower than 9600 there is no delay. For baud rates greater than 9600
the minimum delay is equal to:
Minimum delay after sending “FFh” (in seconds) = 7E-3 – (10/baud rate)
For example, with a baud rate of 38400, the minimum delay after sending “FFh” is:
Minimum delay at 38400 baud = 7E-4 – (10/38400) = 4.4E-4 seconds = 440 µs
Sync Mode generally is intended for applications in which sampling does not occur
frequently. For applications where Sync Mode sampling will be at a frequency of 1 Hz
or higher, there is a minimum allowable delay between taking samples. This minimum
delay between samples (approximately inverse to the maximum sample rate) varies from
100 msec to 1.06 second and is a function of the number of FIR filter taps, as defined by
the following formula:
Minimum Delay between Samples (in seconds) = 0.1 + 0.03*(number of Taps)
7.4.34
kSetModeResps (frame ID 47 d)
This frame is the response to kSetMode frame. The payload contains the Mode ID
requested.
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Payload
Mode ID
UInt8
7.4.35
kSyncRead (frame ID 49 d)
This frame requests a reading from the module when the unit is in Sync Mode. This
frame has no payload. The response to this frame is kDataResp, with heading, pitch, and
roll set as the sequence of data component IDs.
Prior to sending the kSyncRead frame, the user’s system must first send an “FFh” string
which wakes up the system, then wait some minimum delay time before sending the
kSyncRead frame. The minimum delay time is dependent on the baud rate, and for a
baud rate equal to or slower than 9600 there is no delay. The minimum delay is defined
by the same formula given for switching from Sync Mode to Normal Mode in kSetMode.
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7.5
Code Examples
The following example files, CommProtocol.h, CommProtocol.cp, TCM.h and TCM.cp
would be used together for proper communication with a TCM module.
Note: The following files are not included in the sample codes and need to be created by the user:
Processes.h & TickGenerator.h. The comments in the code explain what is needed to be sent or
received from these functions so the user can write this section for the user’s platform. For example,
with the TickGenerator.h, the user needs to write a routing that generates 10 msec ticks.
7.5.1
Header File & CRC-16 Function
// type declarations
typedef struct
{
UInt8 pollingMode, flushFilter;
Float32 sensorAcqTime, intervalRespTime;
} __attribute__ ((packed)) AcqParams;
typedef struct
{
Float32 MagCalScore;
Float32 reserve1;
Float32 AccelCalScore;
Float32 DistErr;
Float32 TiltErr;
Float32 TiltRange;
} __attribute__ ((packed)) CalScore;
enum
{
// Frame IDs (Commands)
kGetModInfo = 1, // 1
kModInfoResp,
// 2
kSetDataComponents,
// 3
kGetData, // 4
kDataResp, // 5
kSetConfig, // 6
kGetConfig, // 7
kConfigResp,
// 8
kSave,
// 9
kStartCal, // 10
kStopCal, // 11
kSetParam, // 12
kGetParam, // 13
kParamResp, // 14
kPowerDown, // 15
kSaveDone, // 16
kUserCalSampCount,
// 17
kUserCalScore,
// 18
kSetConfigDone, // 19
kSetParamDone,
// 20
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kStartIntervalMode,
kStopIntervalMode,
kPowerUp, // 23
kSetAcqParams,
// 24
kGetAcqParams,
// 25
kAcqParamsDone, // 26
kAcqParamsResp, // 27
kPowerDoneDown, // 28
kFactoryUserCal, // 29
kFactoryUserCalDone,
kTakeUserCalSample,
kFactoryInclCal = 36,
kFactoryInclCalDone,
kSetMode = 46,
// 46
kSetModeDone,
// 47
kSyncRead = 49, // 49
// 21
// 22
//
//
//
//
30
31
36
37
// Cal Option IDs
kFullRangeCal = 10,
// 10 - type Float32
k2DCal = 20,
// 20 - type Float32
kHIOnlyCal = 30, // 30 - type Float32
kLimitedTiltCal = 40, // 40 - type Float32
kAccelCalOnly = 100,
// 100 - type Float32
kAccelCalwithMag = 110,
// 110 - type Float32
// Param IDs
kFIRConfig = 3,
// 3- AxisID(UInt8)+Count(UInt8)+Value(Float64)+...
// Data Component IDs
kHeading = 5,
// 5 - type Float32
kTemperature = 7, // 7 - type Float32
kDistortion = 8, // 8 - type boolean
kPAligned = 21, // 21 - type Float32
kRAligned, // 22 - type Float32
kIZAligned, // 23 - type Float32
kPAngle,
// 24 - type Float32
kRAngle,
// 25 - type Float32
kXAligned = 27, // 27 - type Float32
kYAligned, // 28 - type Float32
kZAligned, // 29 - type Float32
// Configuration Parameter IDs
kDeclination = 1, // 1 - type Float32
kTrueNorth, // 2 - type boolean
kMountingRef = 10,
// 10 - type UInt8
kUserCalStableCheck,
// 11 - type boolean
kUserCalNumPoints,
// 12 - type UInt32
kUserCalAutoSampling, // 13 - type boolean
kBaudRate, // 14 - UInt8
kMilOutPut = 15, // 15 - type Boolean
kDataCal
// 16 - type Boolean
kCoeffCopySet = 18,
// 18 - type UInt32
kAccelCoeffCopySet,
// 19 - type UInt32
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// Mounting Reference IDs
kMountedStandard = 1, //
kMountedXUp,
// 2
kMountedYUp,
// 3
kMountedStdPlus90,
//
kMountedStdPlus180,
//
kMountedStdPlus270,
//
kMountedZDown
// 7
kMountedXUpPlus90 // 8
kMountedXUpPlus180
//
kMountedXUpPlus270
//
kMountedYUpPlus90 // 11
kMountedYUpPlus180
//
kMountedYUpPlus270
//
kMountedZDownPlus90
//
kMountedZDownPlus180
//
kMountedZDownPlus270
//
// Result IDs
kErrNone = 0,
kErrSave, // 1
1
4
5
6
9
10
12
13
14
15
16
// 0
};
// function to calculate CRC-16
UInt16 CRC(void * data, UInt32 len)
{
UInt8 * dataPtr = (UInt8 *)data;
UInt32 index = 0;
// Update the CRC for transmitted and received data using
// the CCITT 16bit algorithm (X^16 + X^12 + X^5 + 1).
UInt16 crc = 0;
while(len--)
{
crc = (unsigned char)(crc >> 8) | (crc << 8);
crc ^= dataPtr[index++];
crc ^= (unsigned char)(crc & 0xff) >> 4;
crc ^= (crc << 8) << 4;
crc ^= ((crc & 0xff) << 4) << 1;
}
return crc;
}
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7.5.2
CommProtocol.h File
#pragma once
#include "SystemSerPort.h"
#include "Processes.h"
//
//CommHandler is a base class that provides a callback for
//incoming messages.
//
class CommHandler
{
public:
// Call back to be implemented in derived class.
virtual void HandleComm(UInt8 frameType, void * dataPtr =
NULL, UInt16 dataLen = 0) {}
};
//
// CommProtocol handles the actual serial communication with the //
module.
// Process is a base class that provides CommProtocol with
// cooperative parallel processing. The Control method will be
// called by a process manager on a continuous basis.
//
class CommProtocol : public Process
{
public:
enum
{
// Frame IDs (Commands)
kGetModInfo = 1,
// 1
kModInfoResp,
// 2
kSetDataComponents,
// 3
kGetData,
// 4
kDataResp,
//5
// Data Component IDs
kHeading = 5,
kTemperature = 7,
kPAligned = 21,
kRAligned,
kIZAligned,
kPAngle,
kRAngle,
//
//
//
//
//
//
//
5 - type Float32
7 - type Float32
21 - type Float32
22 - type Float32
23 - type Float32
24 - type Float32
25 - type Float32
};
enum
{
kBufferSize = 512,
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// maximum size of our input buffer
kPacketMinSize = 5
// minimum size of a serial packet
};
// SerPort is a serial communication object abstracting
// the hardware implementation
CommProtocol(CommHandler * handler = NULL,
serPort = NULL);
SerPort
*
void Init(UInt32 baud = 38400);
void SendData(UInt8 frame, void * dataPtr = NULL, UInt32
len = 0);
void SetBaud(UInt32 baud);
protected:
CommHandler * mHandler;
SerPort * mSerialPort;
UInt8 mOutData[kBufferSize], mInData[kBufferSize];
UInt16 mExpectedLen;
UInt32 mOutLen, mOldInLen, mTime, mStep;
UInt16 CRC(void * data, UInt32 len);
void Control();
};
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7.5.3
CommProtocol.cpp File
#include "CommProtocol.h"
// import an object that will provide a 10mSec tick count through
// a function called Ticks()
#include "TickGenerator.h"
// SerPort is an object that controls the physical serial
// interface. It handles sending out
// the characters, and buffers the characters read in until
// we are ready for them.
//
CommProtocol::CommProtocol(CommHandler * handler, SerPort * serPort)
: Process("CommProtocol")
{
mHandler = handler;
// store the object that will parse the data when it is fully
// received
mSerialPort = serPort;
Init();
}
// Initialize the serial port and variables that will control
// this process
void CommProtocol::Init(UInt32 baud)
{
SetBaud(baud);
mOldInLen = 0;
// no data previously received
mStep = 1;
// goto the first step of our process
}
//
// Put together the frame to send to the module
//
void CommProtocol::SendData(UInt8 frameType, void * dataPtr, UInt32
len)
{
UInt8 * data = (UInt8 *)dataPtr;
// the data to send
UInt32 index = 0;
// our location in the frame we are putting together
UInt16 crc;
// the CRC to add to the end of the packet
UInt16 count;
// the total length the packet will be
count = (UInt16)len + kPacketMinSize;
// exit without sending if there is too much data to fit
// inside our packet
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if(len > kBufferSize - kPacketMinSize) return;
//
//
//
//
Store the total len of the packet including the len bytes
(2), the frame ID (1),
the data (len), and the crc (2). If no data is sent, the
min len is 5
mOutData[index++] = count >> 8;
mOutData[index++] = count & 0xFF;
// store the frame ID
mOutData[index++] = frameType ;
// copy the data to be sent
while(len--) mOutData[index++] = *data++;
// compute and add the crc
crc = CRC(mOutData, index);
mOutData[index++] = crc >> 8 ;
mOutData[index++] = crc & 0xFF ;
// Write block will copy and send the data out the serial port
mSerialPort->WriteBlock(mOutData, index);
}
//
// Call the functions in serial port necessary to change the
// baud rate
//
void CommProtocol::SetBaud(UInt32 baud)
{
mSerialPort->SetBaudRate(baud);
mSerialPort->InClear();
// clear any data that was already waiting in the buffer
}
//
// Update the CRC for transmitted and received data using the
// CCITT 16bit algorithm (X^16 + X^12 + X^5 + 1).
//
UInt16 CommProtocol::CRC(void * data, UInt32 len)
{
UInt8 * dataPtr = (UInt8 *)data;
UInt32 index = 0;
UInt16 crc = 0;
while(len--)
{
crc = (unsigned char)(crc >> 8) | (crc << 8);
crc ^= dataPtr[index++];
crc ^= (unsigned char)(crc & 0xff) >> 4;
crc ^= (crc << 8) << 4;
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crc ^= ((crc & 0xff) << 4) << 1;
}
return crc;
}
//
// This is called each time this process gets a turn to execute.
//
void CommProtocol::Control()
{
// InLen returns the number of bytes in the input buffer of
//the serial object that are available for us to read.
UInt32 inLen = mSerialPort->InLen();
//
//
//
//
switch(mStep)
{
case 1:
{
wait for length bytes to be received by the serial object
if(inLen >= 2)
{
Read block will return the number of requested (or available)
bytes that are in the serial objects input buffer.
read the byte count
mSerialPort->ReadBlock(mInData, 2);
// byte count is ALWAYS transmitted in big endian, copy byte
// count to mExpectedLen to native endianess
mExpectedLen
=
(mInData[0]
<<
mInData[1];
8)
|
// Ticks is a timer function. 1 tick = 10msec.
// wait up to 1/2s for the complete frame (mExpectedLen) to be
// received
mTime = Ticks() + 50 ;
mStep++ ;
// goto the next step in the process
}
break ;
}
case 2:
{
// wait for msg complete or timeout
if(inLen >= mExpectedLen - 2)
{
UInt16 crc, crcReceived;
// calculated and received crcs.
// Read block will return the number of
// requested (or available) bytes that are in the
// serial objects input buffer.
mSerialPort->ReadBlock(&mInData[2],
mExpectedLen - 2);
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// in CRC verification, don't include the CRC in the recalculation
(-2)
crc = CRC(mInData, mExpectedLen - 2);
// CRC is also ALWAYS transmitted in big endian
crcReceived = (mInData[mExpectedLen - 2] <<
8) | mInData[mExpectedLen - 1] ;
if(crc == crcReceived)
{
// the crc is correct, so pass the frame up for processing.
if(mHandler)
mHandler>HandleComm(mInData[2], &mInData[3], mExpectedLen - kPacketMinSize);
}
else
{
// crc's don't match so clear everything that is currently in the
// input buffer since the data is not reliable.
mSerialPort->InClear();
}
// go back to looking for the length bytes.
mStep = 1 ;
}
else
{
// Ticks is a timer function. 1 tick = 10msec.
if(Ticks() > mTime)
{
// Corrupted message. We did not get the length we were
// expecting within 1/2sec of receiving the length bytes. Clear
// everything in the input buffer since the data is unreliable
mSerialPort->InClear();
mStep = 1 ;
// Look for the next length bytes
}
}
break ;
}
default:
break ;
}
}
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7.5.4
TCM.h File
#pragma once
#include "Processes.h"
#include "CommProtocol.h"
//
// This file contains the object providing communication to the
// TCM. It will set up the module and parse packets received
// Process is a base class that provides TCM with cooperative
// parallel processing. The Control method will be
// called by a process manager on a continuous basis.
//
class TCM : public Process, public CommHandler
{
public:
TCM(SerPort * serPort);
~TCM();
protected:
CommProtocol * mComm;
UInt32 mStep, mTime, mResponseTime;
void
UInt16 dataLen =
void
UInt16 dataLen =
HandleComm(UInt8 frameType, void * dataPtr = NULL,
0);
SendComm(UInt8 frameType, void * dataPtr = NULL,
0);
void Control();
};
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7.5.5
TCM.cpp File
#include "TCM.h"
#include "TickGenerator.h"
const UInt8 kDataCount = 4;
// We will be requesting 4 componets (Heading, pitch, roll,
// temperature)
//
// This object polls the TCM module once a second for
// heading, pitch, roll and temperature.
//
TCM::TCM(SerPort * serPort)
: Process("TCM")
{
// Let the CommProtocol know this object will handle any
// serial data returned by the module
mComm = new CommProtocol(this, serPort);
mTime = 0;
mStep = 1;
}
TCM::~TCM()
{
}
//
// Called by the CommProtocol object when a frame is completely //
received
//
void TCM::HandleComm(UInt8 frameType, void * dataPtr, UInt16
dataLen)
{
UInt8 * data = (UInt8 *)dataPtr;
switch(frameType)
{
case CommProtocol::kDataResp:
{
// Parse the data response
UInt8 count = data[0];
// The number of data elements returned
UInt32 pntr = 1;
// Used to retrieve the returned elements
// The data elements we requested
Float32 heading, pitch, roll, temperature;
if(count != kDataCount)
{
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// Message is a function that displays a C formatted string
// (similar to printf)
Message("Received %u data elements instead of
the %u requested\r\n", (UInt16)count,
(UInt16)kDataCount);
return;
}
// loop through and collect the elements
while(count)
{
// The elements are received as {type (ie. kHeading), data}
switch(data[pntr++])
// read the type and go to the first byte of the data
{
// Only handling the 4 elements we are looking for
case CommProtocol::kHeading:
{
// Move(source, destination, size (bytes)). Move copies the
// specified number of bytes from the source pointer to the
// destination pointer. Store the heading.
Move(&(data[pntr]),
&heading,
sizeof(heading));
// increase the pointer to point to the next data element type
pntr += sizeof(heading);
break;
}
case CommProtocol::kPAngle:
{
// Move(source, destination, size (bytes)). Move copies the
// specified number of bytes from the source pointer to the
// destination pointer. Store the pitch.
Move(&(data[pntr]),
&pitch,
sizeof(pitch));
// increase the pointer to point to the next data element type
pntr += sizeof(pitch);
break;
}
case CommProtocol::kRAngle:
{
// Move(source, destination, size (bytes)). Move copies the
// specified number of bytes from the source pointer to the
// destination pointer. Store the roll.
Move(&(data[pntr]),
&roll,
sizeof(roll));
// increase the pointer to point to the next data element type
pntr += sizeof(roll);
break;
}
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case CommProtocol::kTemperature:
{
// Move(source, destination, size (bytes)). Move copies the
// specified number of bytes from the source pointer to the
// destination pointer. Store the heading.
Move(&(data[pntr]), &temperature,
sizeof(temperature));
// increase the pointer to point to the next data element type
pntr += sizeof(temperature);
break;
}
default:
// Message is a function that displays a formatted string
// (similar to printf)
Message("Unknown type: %02X\r\n",
data[pntr - 1]);
// unknown data type, so size is unknown, so skip everything
return;
break;
}
count--;
// One less element to read in
}
// Message is a function that displays a formatted string
// (similar to printf)
Message("Heading:
%f,
Pitch:
%f,
Roll:
Temperature: %f\r\n", heading, pitch, roll,
temperature);
mStep--;
// send next data request
break;
}
%f,
default:
{
// Message is a function that displays a formatted string
// (similar to printf)
Message("Unknown
frame
%02X
received\r\n",
(UInt16)frameType);
break;
}
}
}
//
// Have the CommProtocol build and send the frame to the module.
//
void TCM::SendComm(UInt8 frameType, void * dataPtr, UInt16 dataLen)
{
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if(mComm) mComm->SendData(frameType, dataPtr, dataLen);
// Ticks is a timer function. 1 tick = 10msec.
mResponseTime = Ticks() + 300;
// Expect a response
within 3 seconds
}
//
// This is called each time this process gets a turn to execute.
//
void TCM::Control()
{
switch(mStep)
{
case 1:
{
UInt8 pkt[kDataCount + 1];
// the compents we are requesting, preceded by the number of
// components being requested
pkt[0]
pkt[1]
pkt[2]
pkt[3]
pkt[4]
=
=
=
=
=
kDataCount;
CommProtocol::kHeading;
CommProtocol::kPAngle;
CommProtocol::kRAngle;
CommProtocol::kTemperature;
SendComm(CommProtocol::kSetDataComponents,
pkt,
kDataCount + 1);
// Ticks is a timer function. 1 tick = 10msec.
mTime = Ticks() + 100;
// Taking a sample in 1s.
mStep++;
// go to next step of process
break;
}
case 2:
{
// Ticks is a timer function. 1 tick = 10msec.
if(Ticks() > mTime)
{
// tell the module to take a sample
SendComm(CommProtocol::kGetData);
mTime = Ticks() + 100; // take a sample every
second
mStep++;
}
break;
}
case 3:
{
// Ticks is a timer function. 1 tick = 10msec.
if(Ticks() > mResponseTime)
{
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Message("No response from the module.
connection and try again\r\n");
mStep = 0;
}
break;
}
Check
default:
break;
}
}
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