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21 March 2014 04:14 AM

EPO4it Newbie

Total Posts: 3

Joined 2013-06-21

Hello,
I am using a PC with a nRF24AP2-USB based USB dongle. I wrote a program to get the incomming messages of an ANT device. Works all fine. To know which device is beeing received, I turned on the extended messaging format. I used the Lib Config (0x6E) message to enable/disable the three possible extentions. Also works fine, but: The RSSI extended information is 4 bytes and not the 3 bytes documented in "ANT_Message_Protocol_and_Usage_Rev_5.0.pdf".
I looked in the ant_parameter.h header-file and found:
#define ANT_EXT_MESG_RSSI_FIELD_SIZE ((uint8_t)4)
I tried to find more information in this header-file and found some more defines with RSSI_TYPE, but I can not find the clue how to use these defines.
Also I looked at the ANT_AN16_RSSI_Extended_Information.pdf. In this document the RSSI extended format is still 3 bytes.

MY QUESTION: Can you specify how I should interpret the 4 bytes RSSI extended format?

Some outputs in hex:
normal message a4094e0085018017f03dac0392
with device ID a40e4e0086009d000b02ac038062365601da
with RSSI a40e4e00020200000000b00340100068006f
with timestamp a40c4e0005018017f03d90032095920c
with all a4144e00847eb603a6039803e0623656011000680034f0d0

Kind regards, Erik Postma

21 March 2014 11:06 AM #1

usamak Sr. Member

Total Posts: 156

Joined 2013-01-07

PM

Erik,

Tthe nRF24AP2 chip set does not support RSSI measurements.

Section 4.3.1 in the RSSI Extended Application note explains that a value other than 0x20 for the Measurement Type byte (below) indicates that the RSSI value field shall not be interpreted.

Message with RSSI: A4-0E-4E-00-02-02-00-00-00-00-B0-03-40-10-00-68-00-6F

Refer to the Components page (http://www.thisisant.com/developer/components/) for parts that do support RSSI measurement.

24 March 2014 12:39 AM #2

EPO4it Newbie

Total Posts: 3

Joined 2013-06-21

PM

OK, I will not use the RSSI with nRF24AP2-USB based USB dongle.

Still I find it strange, that in the ANT_Message_Protocol_and_Usage_Rev_5.0.pdf document the RSSI is described as 3 bytes extended info and in the ant_parameter.h header-file the RSSI extended info is defined as 4 bytes. May be that should be corrected in the document.

kind regards, Erik

24 March 2014 11:51 AM #3

alejandra Moderator

Total Posts: 662

Joined 2012-10-09

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The RSSI extended information is 3 bytes, the documentation is correct.
Where did you get the ant_parameter.h file from? This file is not part of the official ANT Windows/Mac Library Package.

24 March 2014 04:03 PM #4

EPO4it Newbie

Total Posts: 3

Joined 2013-06-21

PM

The ant_parameters.h header file is part of the nRF51-SDK. This is distributed by Nordic with the nRF51422 developer kit. The header file is located at nrf51sdk/Nordic/nrf51422/Include/ant/softdevice/ant_parameters.h . I have also attached the file. At line 408 you can see:
#define ANT_EXT_MESG_RSSI_FIELD_SIZE ((uint8_t)4)

The nRF24AP2-USB based USB dongle also have 4 bytes extra, when the RSSI bit is set with antLibConf(). You can see it in the message, I put in my first writing. It is also in your reply, where you bolded the hex 10.
A4-0E-4E-00-02-02-00-00-00-00-B0-03- 40- (config-flags) 10-00-68-00 (four bytes extended RSSI) -6F (CRC)

kind regards, Erik

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ant_parameter.zip (File Size: 7KB - Downloads: 502)

25 March 2014 10:30 AM #5

usamak Sr. Member

Total Posts: 156

Joined 2013-01-07

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Erik,

Thanks for pointing this out. We will add a fix for the next Nordic nRF51 SDK update.

We will look into updating our documentation so users are aware that the AP2 returns a 4 byte value for RSSI, in the case RSSI is enabled (which is not recommended).

11 January 2016 04:40 PM #6

chris.ingraham Newbie

Total Posts: 1

Joined 2013-09-11

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I too was trying to get RSSI information out of the nRF24AP2 chip and the "Measurement Type" byte was always returning 0x10. Is it true that this device does not support RSSI reporting?

If it does not support RSSI reporting, is there any other means by which I could determine the signal strength? I currently have a problem where a new hardware design is intermittently loosing packets, and I was trying to determine if we had a problem with the hardware (antenna, layout, etc) since the same software seems to run fine on the older design.

ANT Forum

RSSI extended messaging format

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