M AESTRO GPS - A PPS N OTE
GPSC3 F IRMWARE REV 0.1
A DESCRIPTION OF USEFUL MODES SUPPORTED VIA THE S I RF BINARY PROTOCOL
ON M AESTRO W IRELESS S OLUTIONS ’ S GPS MODULES BASED ON S I RF III - GSC3
A1080A, A1084, A1088A, A1035H
F IRMWARE 3.6.0
WWW. MAESTRO - WIRELESS . COM
E MAIL : CONTACT @ MAESTRO - WIRELESS . COM
T EL : (+852) 2869 0688
FAX : (+852) 2525 4701
A DDRESS : R OOM 3603-3609, 36/F, 118 C ONNAUGHT R OAD W EST, S HEUNG WAN , H ONG KONG
Revision history
Rev.
0.0
0.1
Date
22 March 2011
6 April 2011
Details
First issue
CSR approved. Updated for revision 3.6.0 FW.
Originated by
Samuel Chereau
Samuel Chereau
This manual is written without any warranty.
Maestro Wireless Solutions Ltd. reserves the right to modify or improve the product and its accessories
which can also be withdrawn without prior notice.
Besides, our company stresses the fact that the performance of the product as well as accessories depends
not only on the proper conditions of use, but also on the environment around the places of use.
Maestro Wireless Solutions Ltd. assumes no liability for damage incurred directly or indirectly from errors,
omissions or discrepancies between the modem and the manual.
Confidential, the whole document is the sole property of Maestro Wireless Solutions ltd.
3603-9, 36/F., 118 Connaught Road West, Sheung Wan, Hong Kong
contact@maestro-wireless.com
1
Contents
1 Introduction
4
2 NMEA and Binary mode
5
2.1 From NMEA to Binary Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
2.2 From Binary to NMEA Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
2.3 SiRFDemo Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
3 Push-To-Fix Mode
8
3.1 Necessary Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
3.1.1 Set Trickle Power Parameters – Message ID 151 . . . . . . . . . . . . . . . . . . . . . .
8
3.1.2 Set Low Power Acquisition Parameters – Message ID 167 . . . . . . . . . . . . . . . . .
9
3.2 Exit Push-To-Fix Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
3.3 Summary of Main Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
4 SBAS Support
12
5 Static Mode
13
6 Shutdown Module
15
7 Related Information
16
7.1 Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
7.2 Related Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
7.3 Related Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17
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contact@maestro-wireless.com
2
List of Tables
2.1 Serial Port Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
3.1 Set trickle power mode parameters (enter) – Message ID 151 . . . . . . . . . . . . . . . . . . .
9
3.2 Set low power acquisition parameters – Message ID 167 . . . . . . . . . . . . . . . . . . . . . .
9
3.3 Push-to-fix mode examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
3.4 Set trickle power mode parameters (exit) – Message ID 151 . . . . . . . . . . . . . . . . . . . .
10
4.1 DGPS source selection – Message ID 133 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
5.1 Static Navigation enable – Message ID 143 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
5.2 Navigation disable – Message ID 143 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
6.1 Shutdown module – Message ID 205 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15
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3
Chapter 1
Introduction
The intention of the application notes described in this document is to help customers make use of the most
important features of Maestro Wireless Solutions’s SiRFstarIII - GSC3-based products. This document is a
living document; it mostly explains the software commands necessary to support the different features but also
tries to explain the background of these features.
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4
Chapter 2
NMEA and Binary mode
By default Maestro Wireless Solutions receivers start off in NMEA mode. You can get the well known NMEA
sentences, switch them on or off - but not much more. In order to go deeper into the SiRFstarIII configuration,
it is necessary to switch to binary mode.
2.1
From NMEA to Binary Mode
This is done using the following NMEA command (note that the baud rate can be different):
– $PSRF100,0,57600,8,1,0*37
Refer to the Table 2.1 for a more general description on the PSRF100 command that allows switching to SiRF
binary protocol.
Name
Message ID
Protocol
Baud
DataBits
StopBits
Parity
Checksum
Example
$PSRF100
0
57600
8
1
0
*37
Description
PSRF100 protocol header
0 SiRF binary / 1 NMEA
4800, 9600, 19200, 38400, 57600, 115200
8, 7
0, 1
0 none / 1 odd / 2 even
End of message termination
Table 2.1: Serial Port Setup
After that information from the module and commands to the module are transmitted in SiRF binary protocol
mode. For details please refer to the according manual.
This command has no impact on the serial port used. All data exchange will be done via port 0.
If backed by a battery (Vbak), the module will store the configuration and reboot after a reset in the very same
way. If completely powered off, the module will start in default NMEA mode again.
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5
2.2
From Binary to NMEA Mode
When you configured the module you might wish to go back to NMEA mode in or-der to get the PVT information
in the standard, familiar way. In order to do that, you can use the following binary command sequence:
A0A200188102010100010101010101010001000100010001000112C00163B0B3
Within this message one can determine the following segments (this applies gener-ally to all SiRF binary
commands):
A0A20018 − S t a r t Sequence ( A0A2 ) and Payload Length ( 0 x18 = 24)
8102 0101 0001 0101 0101 0101 0001 0001 0001 0001 0001 12C0 − Payload
0163B0B3 − Message Checksum ( 0 1 6 3 ) and End Sequence ( B0B3 )
Name
Message ID
Mode
GGA Messagea
Checksumb
GLL Message
Checksum
GSA Message
Checksum
GSV Message
Checksum
RMC Message
Checksum
VTG Message
Checksum
MSS Message
Checksum
Unused fieldc
Unused field
ZDA Message
Checksum
Unused field
Unused field
Bit rate
Bytes
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
1U
2U
Example
0x81
0x02
0x01
0x01
0x00
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x00
0x01
0x00
0x01
0x00
0x01
0x00
0x01
0x00
0x01
0x12C0
Unit
s
Description
Decimal 129
Do not change last-set value for NMEA debug
See NMEA Protocol Reference Manual for format
Send checksum with GGA message
See NMEA Protocol Reference Manual for format
s
See NMEA Protocol Reference Manual for format
s
See NMEA Protocol Reference Manual for format
s
See NMEA Protocol Reference Manual for format
s
See NMEA Protocol Reference Manual for format
s
Output rate for MSS message (always zero, as not supported here)
s
See NMEA Protocol Reference Manual for format
s
1200, 2400, 4800, 9600, 19200, 38400, and 57600
Switch to NMEA mode – Message ID 129
a A value of 0x00 implies not to send message, otherwise data is sent at 1 message every X seconds re-quested (e.g., to request a
message to be sent every 5 seconds, request the message using a value of 0x05). Maximum rate is 1/255 sec.
b A value of 0x00 implies the checksum is not transmitted with the message (not recommended). A value of 0x01 has a checksum
calculated and transmitted as part of the message (recommended).
c These fields are available if additional messages have been implemented in the NMEA protocol.
So this command would result in switching to NMEA mode with a baud rate of 4800 bits per second and the
following configuration:
GGA – ON at 1 sec, GLL – OFF, GSA – ON at 1sec, GSV – ON at 1 sec, RMC – ON at 1sec, VTG - OFF, MSS
– OFF, ZDA - OFF.
After that information from the module and commands to the module are transmitted in NMEA format again.
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For details please refer to the according manual.
This command has no impact on the serial port used. All data exchange will be done via port 0.
If backed by a battery (Vbak), the module will store the configuration and reboot after a reset in the very same
way. If completely powered off, the module will start with the default NMEA settings.
2.3
SiRFDemo Software
A useful tool to test and evaluate SiRF binary commands is the SiRFDemo Software. This tool is available
from Maestro Wireless. Please contact your local sales representative if you should need this tool. Detailed
information about the tool is available in the SiRFDemo User Guide.
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Chapter 3
Push-To-Fix Mode
The goal of using this mode is to keep the receiver always in a state where it has more or less the latest satellite
information (Ephemeris data) – after initialization without any further external engagement. When then finally
being awakened by an external microcontroller the receiver can perform a hot start with a very short time to
fix. Along with the sleep cycles this will result in an excellent power budget.
Initialized to this mode the receiver turns on every cycle period to perform a system update consisting of an
RTC calibration and satellite ephemeris data collection if required. This is the case when a new satellite has
become visible or validity of old Ephemeris data did expire. In addition it performs all software tasks to support
a quick fix request in the event of a Non-Maskable Interrupt (NMI). If Ephemeris data collection is not required
then the system recalibrates and shuts down. Ephemeris collection time in general takes 18 to 36 seconds.
A fix request is initiated by toggling the module’s ON_OFF pin (see also: Receiver Manual) – resulting in an
internal NMI. Note that the toggling should be performed only when RFPWUP is low, i.e. when the receiver is
sleeping. When a fix request was initiated the module will calculate at least one fix, try to update Ephemeris
data and go back to sleep.
3.1
Necessary Steps
To put the receiver into push-to-fix mode, two commands are necessary. First of all, the receiver has to be
brought into push-to-fix mode using the trickle power mode command. Anyhow, one has to see that trickle
power mode and push-to-fix mode are two different things! In a further step push-to-fix parameters have to be
defined.
3.1.1
Set Trickle Power Parameters – Message ID 151
A0A2000997000103E8000000C8024BB0B3
Within this message one can determine the following segments, refer to the Table 3.4:
A0A20009 − S t a r t Sequence ( A0A2 ) and Payload Length ( 0 x09 = 9 )
97000103E8000000C8 − Payload
024BB0B3 − Message Checksum (024B ) and End Sequence ( B0B3 )
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Name
Message ID
PTF Mode
Bytes
1U
2S
Scale
Example
0x97
0x0001
Unit
Duty Cycle
2U
*10
0x03E8
%
On time
4U
*10
0x000000C8
ms
Description
Decimal 151
0 = OFF, 1 = ON (here)
% time ON. A duty cycle of 1000 (100%) means
continuous operation. Here: 1000.
Trickle power mode settings are unused!
Allowed range 200 – 900ms. Here: 200ms.
Only used, when duty cycle is different from
1000, so meaningless here!
a
a
Table 3.1: Set trickle power mode parameters (enter) – Message ID 151
So this way we tell the receiver to switch to push-to-fix mode.
3.1.2
Set Low Power Acquisition Parameters – Message ID 167
A0A2000FA70001D4C0000075300000012C0000030EB0B3
Within this message one can determine the following segments, refer to the Table 3.2 :
A0A2000F − S t a r t Sequence ( A0A2 ) and Payload Length ( 0 x0F = 15)
A70001D4C0000075300000012C0000 − Payload
030EB0B3 − Message Checksum (030E) and End Sequence ( B0B3 )
Name
Message ID
Bytes
1U
Max. Off Time
Max. Search
Time
Push-to-fix
Period
Adaptive T.P.
Scale
Example
0xA7
Unit
4S
0x0001D4C0
ms
4U
0x00007530
ms
4U
0x0000012C
s
2U
0x0000
s
Description
Decimal 167
Max. time for sleep mode, default 30s, here
120000ms = 120s
Max. satellite search time, default 120s, here
30000ms = 30s
Push-to-fix cycle period, here 300s
a Always 0!
Table 3.2: Set low power acquisition parameters – Message ID 167
Maximum Off Time
The receiver turns on after the maximum off time, if the receiver could not catch satellite signals within the
maximum search time during the last attempt.
Maximum Search time
This is the maximum time period the receiver tries to catch satellite signals. The receiver will go back to standby if the receiver cannot receive satellite signals within this period and will try it again after the maximum off
time.
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PTF Period
This is the PTF cycle period. The receiver turns on automatically to perform a system update.
Examples - Table 3.3
Max. Off
Time (s)
120
Parameters
Max. Search
Time (s)
30
PTF Period
(s)
300
1800
30
1800
2100
30
4200
Command (Hexa)
Comment
A0A2000FA70001D4C0000075
300000012C0000030EB0B3
A0A2000FA7001B7740000075
30000007080000022DB0B3
A0A2000FA700200B20000075
30000010680000020FB0B3
Test setting
SiRF recommended
default setting
Test setting
Table 3.3: Push-to-fix mode examples
3.2
Exit Push-To-Fix Mode
To exit from push-to-fix mode, the according command needs to be sent while the receiver is awake. If the
receiver is awake can be detected by checking if anything (NMEA or binary information) is transmitted by the
receiver or by looking at the pins RFWUP (High = ON) or nWakeup (Low = ON). Naturally, the receiver will be
also awake after a fix request (toggling of ON_OFF pin) was done.
The following message will bring back the receiver to normal operation. Of course the receiver needs to be
put into binary command mode before.
A0A2000997000003E8000000C8024AB0B3
Within this message one can determine the following segments, refer to the Table 3.4:
A0A20009 − S t a r t Sequence ( A0A2 ) and Payload Length ( 0 x09 = 9 )
97000003E8000000C8 − Payload
024AB0B3 − Message Checksum (024A ) and End Sequence ( B0B3 )
Name
Message ID
PRF Mode
Bytes
1U
2S
Scale
Example
0x97
0x0000
Duty Cycle
2U
*10
0x03E8
On Time
4U
*10
0x000000C8
Unit
Description
Decimal 151
0 = OFF (here), 1 = ON
% time ON. A duty cycle of 1000 (100%) means
continuous operation. Here: 1000.
Don’t use any trickle power mode settings!
Allowed range 200 – 900ms. Here: 200ms.
Only used, when duty cycle is different from
1000, so meaningless here!
a
a
Table 3.4: Set trickle power mode parameters (exit) – Message ID 151
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3.3
Summary of Main Advantages
The push-to-fix mode gives the following advantages:
– One initialization – no further engagement from external microcontroller
– Receiver is always up-to-date with Ephemeris data (of course, if satellites are „visible“)
– Whenever awakened it is ready for a hot start
– This results in a minimum TTFF
– Total power budget optimized
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Chapter 4
SBAS Support
The SiRFstarIII chip set supports the Satellite Based Augmentation System (SBAS) a kind of Differential GPS
(DGPS) via satellite. The advantage of SBAS towards traditional DGPS lies in the fact that correctional data
are received on a normal GPS channel. Therefore the receiver can use one of its 20 channels to detect and
decode SBAS information. There is no need for an additional external receiver.
To initialize SBAS mode it is necessary to send the message with ID 133 (DGPS source) to the receiver –
which has to be put into binary mode before.
A0A20007850100000000000086B0B3
Within this message one can determine the following segments, refer to the Table 4.1:
A0A20007 − S t a r t Sequence ( A0A2 ) and Payload Length ( 0 x07 = 7 )
85010000000000 − Payload
0086B0B3 − Message Checksum ( 0 0 8 6 ) and End Sequence ( B0B3 )
Name
Message ID
Bytes
1U
DGPS Source
1U
0x01
4U
0x00000000
Not used!
1U
0x00
Not used!
Internal beacon
frequency
Internal beacon
bit rate
Scale
Example
0x85
Unit
Description
Decimal 133
0 = None
1 = SBAS (here)
2 = External RTCM data
3 = Internal DGPS beacon receiver
4 = User software
Table 4.1: DGPS source selection – Message ID 133
By default the receiver will find the right SBAS satellite automatically. One can select a specific SBAS satellite
using message ID 170. Please refer to the SiRF Binary Reference Manual for details.
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Chapter 5
Static Mode
Static navigation is a position filter designed to be used with applications intended for motor vehicles. When
the vehicle’s speed falls below a threshold, the position and heading are frozen, and speed is set to zero.
This condition continues until the computed speed rises above 1.2 times the threshold or until the computed
position is at least a set distance from the frozen place. The threshold speed and set distance may vary with
software versions, currently the thresholds are as follows:
– Speed: ~ 3km/h
– Position: ~ 50m
These thresholds are fixed and cannot be modified by the user. Also, with the static mode one cannot reach a
higher accuracy! But one will avoid small jumps due to the “noise” in the GPS signals and receiver.
To initialize static mode it is necessary to send the message with ID 143 to the receiver – which has to be put
into binary mode before.
A0A200028F010090B0B3
Within this message one can determine the following segments, refer to the Table 5.1:
A0A20002 − S t a r t Sequence ( A0A2 ) and Payload Length ( 0 x02 = 2 )
8F01 − Payload
0090B0B3 − Message Checksum ( 0 0 9 0 ) and End Sequence ( B0B3 )
Name
Message ID
Static
Navigation Flag
Bytes
1U
1U
Scale
Example
0x8F
Unit
0x01
Description
Decimal 143
0 = Enable (here)
1 = Disable
Table 5.1: Static Navigation enable – Message ID 143
To disable static mode, the according command would be:
A0A200028F00008FB0B3
Within this message one can determine the following segments, refer to the Table 5.2:
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A0A20002 − S t a r t Sequence ( A0A2 ) and Payload Length ( 0 x02 = 2 )
8F00 − Payload
008FB0B3 − Message Checksum (008F ) and End Sequence ( B0B3 )
Name
Message ID
Static
Navigation Flag
Bytes
1U
1U
Scale
Example
0x8F
Unit
0x00
Description
Decimal 143
0 = Enable
1 = Disable (here)
Table 5.2: Navigation disable – Message ID 143
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Chapter 6
Shutdown Module
This command is available starting with firmware version 3.5.0 only!
All GSC3-based GPS modules will enter hibernate mode after this command has been issued. Data in SRAM
are being maintained, the RTC will keep on running.
To shutdown the module it is necessary to send the message with ID 205 along with Sub ID 16 to the receiver
– which has to be put into binary mode before.
A0A20002CD1000DDB0B3
Within this message one can determine the following segments:
A0A20002 − S t a r t Sequence ( A0A2 ) and Payload Length ( 0 x02 = 2 )
CD10 − Payload
00DDB0B3 − Message Checksum (00DD) and End Sequence ( B0B3 )
Name
Message ID
Message Sub
ID
Bytes
1U
1U
Scale
Example
0xCD
0x10
Unit
Description
Decimal 205
Message Sub ID for software command off
Table 6.1: Shutdown module – Message ID 205
Note: The SiRF Binary Manual shows a payload length of 0 bytes. This is incorrect. Please use the payload
length of 2 bytes as described here.
To wake up the GPS module again one of the following methods can be used:
– Toggle ON-OFF
– Toggle nReset
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Chapter 7
Related Information
7.1
Contact
This manual was created with due diligence. We hope that it will be helpful to the user to get the most out of
the GPS module.
Inputs regarding errors or mistaken verbalization and comments or proposals to Maestro Wireless Solutions,
for further improvements are highly appreciated.
www.maestro-wireless.com
Email: contact@maestro-wireless.com
Tel: (+852) 2869 0688
Fax: (+852) 2525 4701
Address: Room 3603-3609, 36/F, 118 Connaught Road West, Sheung Wan, Hong Kong
7.2
Related Documents
– SiRF_NMEA_Reference_Manual_2.2 (CSR)
– SiRF_Binary_Reference_Manual_2.4 (CSR)
– GPS Receiver A1080A (Maestro Wireless Solutions)
– GPS Evaluation Kit EVA1080A (Maestro Wireless Solutions)
– GPS Receiver A1084 (Maestro Wireless Solutions)
– GPS Evaluation Kit EVA1084 (Maestro Wireless Solutions)
– GPS Receiver A1088 (Maestro Wireless Solutions)
– GPS Evaluation Kit EVA1088 (Maestro Wireless Solutions)
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16
– GPS Receiver A1035-H (Maestro Wireless Solutions)
– GPS Evaluation Kit EVA1035-H (Maestro Wireless Solutions)
7.3
Related Tools
– GPS Cockpit (Maestro Wireless Solutions)
– SiRF Live (CSR)
– SiRF Flash (CSR)
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17