Texas Instruments | DN022 -- CC110x CC111x OOK ASK Register Settings (Rev. E) | Application notes | Texas Instruments DN022 -- CC110x CC111x OOK ASK Register Settings (Rev. E) Application notes

Texas Instruments DN022 -- CC110x CC111x OOK ASK Register Settings (Rev. E) Application notes
Design Note DN022
CC110x/CC111x OOK/ASK Register Settings
By Sverre Hellan
Keywords
OOK
ASK
PER (Packet Error Rate)
CC1100
CC1100E
1
CC1101
CC1110
CC1111
CC430
Introduction
This design note provides guidelines for
finding optimum register settings for
OOK/ASK operation. The starting point for
the optimization is the preferred settings
®
given by the SmartRF Studio SW. The
user needs to measure the sensitivity
(PER) over the full input dynamic range to
determine the optimum settings.
This design note uses CC1101 as an
example on how to find optimum register
settings, but it is also applicable for
CC1100, CC1100E, CC1110, CC1111,
and CC430.
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Design Note DN022
Table of Contents
KEYWORDS.............................................................................................................................. 1
1
INTRODUCTION ............................................................................................................. 1
2
ABBREVIATIONS ........................................................................................................... 2
3
OOK/ASK REGISTER SETTINGS ................................................................................. 3
3.1
AGC SETTINGS ......................................................................................................... 3
3.2
IF FREQUENCY .......................................................................................................... 4
®
3.3
PROCEDURE FOR FINDING OOK/ASK SETTINGS USING SMARTRF STUDIO................. 5
4
GENERAL INFORMATION ............................................................................................. 8
4.1
DOCUMENT HISTORY ................................................................................................. 8
2
Abbreviations
AGC
ASK
EM
2-FSK
GFSK
IF
MSK
OOK
PER
SW
Automatic Gain Control
Amplitude Shift Keying
Evaluation Module
Frequency Shift Keying
Gaussian shaped Frequency Shift Keying
Intermediate Frequency
Minimum Shift Keying
On-Off Keying
Packet Error Rate
Software
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Design Note DN022
3
3.1
OOK/ASK Register Settings
AGC Settings
®
The register settings provided by SmartRF Studio have been optimized for 2FSK/GFSK/MSK modulation and when using one of the preferred settings and only changing
the modulation format to OOK/ASK, the AGC settings might result in unstable or non-optimum
reception (i.e. degraded sensitivity). This is pictured in Figure 1.
120
100
PER [%]
80
non-optimum
optimum
unstable
60
40
20
0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
-70
-75
-80
-85
-90
-95
-100
-105
-110
-115
-120
0
Input power level [dBm]
Figure 1. Example of Unstable, Non-Optimum, and Optimum Reception
The optimum AGC settings change with RX filter bandwidth and data rate, but for OOK/ASK
the following has been found to give good results:
AGCCTRL2 = 0x03 to 0x07
AGCCTRL1 = 0x00
AGCCTRL0 = 0x91 or 0x92
In the example shown in Figure 2, the best sensitivity is achieved with AGCCTRL2 = 0x04,
AGCCTRL1 = 0x00, and AGCCTRL0 = 0x92. Please note that optimum register settings
change with data rate so it is important to measure sensitivity for different combinations of
AGCCTRL2 and AGCCTRL0. Furthermore, as shown in Figure 1, some combinations of AGC
settings results in unstable reception. That is, for some input power levels above the sensitivity
limit there will be degraded packet error rate (PER). It is therefore important to check the PER
for the entire dynamic range and not only at the sensitivity limit. One option is to check the
PER for every 2 dB increase in input power level.
AGCCTRL2.MAGN_TARGET[2:0] is used to set an on-chip target value for the peak signal
amplitude. MAGN_TARGET is used by the AGC loop to set the correct gain.
AGCCTRL0.FILTER_LENGTH[1:0] is used to configure the ASK decision boundary. If the
ASK decision boundary is set to 8 dB, the “low” bit must be at least 16 dB below the “high” bit.
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Design Note DN022
120
100
PER [%]
80
07 00 92
06 00 92
05 00 92
04 00 92
03 00 92
60
40
20
-1
2
-1
8
-2
4
-3
0
-3
6
-4
2
-4
8
-5
4
-6
0
-6
6
-7
2
-7
8
-8
4
-9
0
-9
6
-1
02
-1
08
-1
14
-1
20
0
Input power level [dBm]
Figure 2. PER versus Input Power Level for Different AGC Register Settings (3.8 kBaud,
100 kHz RX Filter Bandwidth)
3.2
IF Frequency
Register FSCTRL1 sets the IF frequency and the optimum value is different for different RX
filter bandwidths. It is therefore recommended to find the FSCTRL1 setting using one of the
®
preferred RX filter bandwidth settings in SmartRF Studio (see Figure 3). If the wanted RX
filter bandwidth is not given by one of the preferred settings, choose the FSCTRL1 setting for
the first RX filter bandwidth that is wider than the wanted RX filter bandwidth.
As an example, for a wanted 150 kHz RX filter bandwidth use the FSCTRL1 setting given for
232 kHz RX filter bandwidth.
RX filter bandwidths
used by preferred settings:
58 kHz, 100 kHz, 232 kHz,
325 kHz, 540 kHz, 812 kHz
Figure 3. Available RX Filter Bandwidths Given by the Preferred Settings in SmartRF
Studio
SWRA215E
®
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Design Note DN022
Note that the FREND1, FIFOTHR, TEST2, and TEST1 register settings change for different
RX filter bandwidths.
FREND1:
RX filter bandwidth > 101 kHz, FREND1 = 0xB6
RX filter bandwidth ≤ 101 kHz, FREND1 = 0x56
TEST2:
RX filter bandwidth > 325 kHz, TEST2 = 0x88
RX filter bandwidth ≤ 325 kHz, TEST2 = 0x81
TEST1:
RX filter bandwidth > 325 kHz, TEST1 = 0x31
RX filter bandwidth ≤ 325 kHz, TEST1 = 0x35
FIFOTHR:
RX filter bandwidth > 325 kHz, FIFOTHR = 0x07
RX filter bandwidth ≤ 325 kHz, FIFOTHR = 0x47
3.3
®
Procedure for Finding OOK/ASK Settings using SmartRF Studio
As an example, assume 4.8 kBaud data rate and 203 kHz RX filter bandwidth.
®
1) Use SmartRF Studio to find the optimum IF frequency. Select the preferred setting that
has an RX filter bandwidth equal to the wanted bandwidth. If the wanted RX filter bandwidth is
not given by one of the preferred settings, chose the first RX filter bandwidth that is wider than
the wanted bandwidth. For a 203 kHz wanted RX filter bandwidth, select the 232 kHz RX filter
bandwidth for optimum IF frequency.
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Design Note DN022
2) Change the data rate and the RX filter bandwidth to the wanted values. Change the
®
modulation format to ASK/OOK. Press “Reset CC1101 and write settings” (if SmartRF Studio
is being used to control a CC1101EM) and then “Copy settings to Register View”
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Design Note DN022
3) In Register View, change the AGCCTRL2, AGCCTRL1, and AGCCTRL0 settings as
explained in Section 3.1. Make sure the FSCTRL1, FIFOTHR, FREND1, TEST2, and TEST1
registers are set as explained in Section 3.2. It is possible to print the register settings to a file
using “Export CC1101 Registers” under “File”. Press the “Write” button for the register to be
®
updated if SmartRF Studio is being used to control a CC1101EM.
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Design Note DN022
®
4) If SmartRF Studio is being used to perform the test, go back to Normal View. Check the
Manual Init box for the changes done in Register View to take effect.
4
4.1
General Information
Document History
Revision
SWRA215E
Date
2012-03-08
SWRA215D
SWRA215C
SWRA215B
SWRA215A
2012-02-10
2012-02-09
2009-11-11
2009-03-15
SWRA215
2008-06-09
Description/Changes
Changed document name from “CC11xx OOK/ASK Register
Settings” to “CC110x/CC111x OOK/ASK Register Settings”
Corrected error in RX BW on page 5
Added FIFOTHR to the list of registers on page 5
Added CC430 to list of devices
Added CC1100E. Added info about TEST2, TEST1, and FREND1
register settings for wide RX filter bandwidths.
Initial release
SWRA215E
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