dronecan 1140.RCInput: add flags to represent LQ, RSSi dbm and SNR li…

…nk statistics

dronecan/sensors/rc/1140.RCInput.uavcan

@@ -1,9 +1,27 @@
-uint8 STATUS_QUALITY_VALID = 1 # quality field is valid
+#
+# RC channels
+#
+# The quality field can carry different information on the quality of a radio link, as determined by the flags in the status bitmask:
+# - STATUS_QUALITY_VALID: The quality field is valid and represents RSSI in scaled units, 0 is no signal, 255 is "full" signal. The
+#   mapping of a link's internal RSSI representation onto the scaled units is device dependent. A common mapping can be
+#     RSSI >= -50 dB: 255
+#     RSSI > -120 dB and RSSI < -50 dBm: 255 / 70 * (RSSI + 120) but not smaller than 1
+#     RSSI <= -120 dB: 1
+# - STATUS_QUALITY_LQ: The quality field is valid and represents LQ in percent, 0 is no signal, 100 is 100% link quality
+# - STATUS_QUALITY_RSSI_DBM: The quality field is valid and represents RSSI in inverted dBm, 0 is no signal, 1 = -1 dBm, 255 = -255 dBm
+# - STATUS_QUALITY_SNR: The quality field is valid and represents SNR in device dependent units, value is shifted by 128 to allow
+#   representing positive and negative values: 128 = 0, 255 = +127, 1 = -127, 0 is no signal
+# Only one of these flags can be set at any time.
+
+uint8 STATUS_QUALITY_VALID = 1 # quality field is valid and represents RSSI in scaled uints, 0 is no signal, 255 is "full" signal
 uint8 STATUS_FAILSAFE = 2 # receiver has lost contact with transmitter
+uint8 STATUS_QUALITY_LQ = 4 # quality field is valid and represents LQ in percent, 0 is no signal, 100 is 100% link quality
+uint8 STATUS_QUALITY_RSSI_DBM = 8 # rssi in inverted dBm, 0 is no signal, 1 = -1 dBm, 255 = -255 dBm
+uint8 STATUS_QUALITY_SNR = 16 # quality field is valid and represents SNR in device dependent units, shifted by 128
 
 uint16 status      # bitmask of status bits, enumerated above with STATUS_*
 
-uint8 quality      # scaled, 0 is no signal, 255 is "full" signal
+uint8 quality      # see descriptions for status bits STATUS_QUALITY_VALID, STATUS_QUALITY_LQ, STATUS_QUALITY_SNR
 uint4 id           # ID of this RC input device
 
-uint12[<=32] rcin  # RC channel values between 0 and 4095
+uint12[<=32] rcin  # RC channel values between 0 and 4095, 2048 represents the mid position