Bad Mavlink RSSI when not connected

[InanixFR]

Hello,

When I start my drone, without starting the ground station I wan see the mavlink Message RADIO_STATUS

{
  "fixed": 0,
  "noise": 0,
  "remnoise": 1,
  "remrssi": 128,
  "rssi": 128,
  "rxerrors": 0,
  "txbuf": 100,
  "type": "RADIO_STATUS"
}

As you can see the rssi values are set to 128.

I think the problem comes from the line 293 of file wfb-ng/wfb_ng
/server.py

mav_rssi = (max(card_rssi_l) if card_rssi_l else -128) % 256

If I set WFB in debug, I got those 2 lines :
mavlink rx rssi N/A tx#0 {'all': (0, 0), 'all_bytes': (0, 0), 'dec_ok': (0, 0), 'fec_rec': (0, 0), 'lost': (0, 0), 'dec_err': (0, 0), 'bad': (0, 0), 'out': (0, 0), 'out_bytes': (0, 0)} {}
tunnel tx {'fec_timeouts': (0, 0), 'incoming': (0, 8), 'incoming_bytes': (0, 200), 'injected': (0, 23), 'injected_bytes': (0, 1464), 'dropped': (0, 0), 'truncated': (0, 0)} {}

And (-)128 modulo 256 equals 128.
In this case the RSSI should be 0, or a very low value. Putting -256 instead of -128 and we should get 0
mav_rssi = (max(card_rssi_l) if card_rssi_l else -256) % 256

What do you think about ?

[svpcom]

This is because MAVLINK_MSG_ID_RADIO_STATUS has uint8_t as type for rssi, but rssi is signed. So need to convert it to unsigned value with sign bit set. So unsigned 128 is equal to -128

import struct
>>> struct.unpack('bbbb', bytes([128, 129, 130, 200]))
(-128, -127, -126, -56)

[InanixFR]

Thanks for reply