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markqvist / RNode_Firmware

RNode is an open, free and flexible digital radio interface with many uses
https://unsigned.io/rnode
GNU General Public License v3.0
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RSSI & SNR values on SX1262 may be incorrect #60

Closed jacobeva closed 8 months ago

jacobeva commented 8 months ago

There is currently no way to verify the RSSI & SNR values of the SX1262 are being correctly handled by the driver (to my knowledge), I need to check these values seem reasonable (they probably aren't) and fix them if not. https://github.com/markqvist/RNode_Firmware/issues/59 must be resolved first to allow me to retrieve the RSSI & SNR values if I'm correct.

jacobeva commented 8 months ago

Values retrieved look normal. For context the radios are about 30cm apart. Here's the output for reference: Round-trip time is 798.89 milliseconds over 1 hop [RSSI 68 dBm] [SNR 14.25 dB] [Link Quality 100.0%] Closing...

Edit: Apologies for the noise.

markqvist commented 8 months ago

RSSI seems quite off. If 68dBm is reaching the modem, it would be receiving more than 6.3 kilowatts on the antenna. Now, I don't know what kind of transceiver you're designing here, but I now expect some dramatically serious equipment :)

Joking aside, there should be an offset value or calculation somewhere in the datasheet.

jacobeva commented 8 months ago

The RSSI issue has now been fixed. I wasn't adding the offset in the firmware, and on top of that an unsigned integer was being used for a negative value, causing the reported value to be something in the range of 200 (!) once the offset was added. Both are now corrected, but I suspect there is something wrong with the setTXPower function too, which I will be investigating later today. All my changes will be proposed in a PR.

markqvist commented 8 months ago

Fixed by #62.