Crossfire: add barometer altitude sensor (#232)

radio/src/telemetry/crossfire.cpp

@@ -51,6 +51,7 @@ const CrossfireSensor crossfireSensors[] = {
     {ATTITUDE_ID, 2, ZSTR_YAW, UNIT_RADIANS, 3},
     {FLIGHT_MODE_ID, 0, ZSTR_FLIGHT_MODE, UNIT_TEXT, 0},
     {CF_VARIO_ID, 0, ZSTR_VSPD, UNIT_METERS_PER_SECOND, 2},
+    {BARO_ALT_ID, 0, ZSTR_ALT, UNIT_METERS, 2},
     {0, 0, "UNKNOWN", UNIT_RAW, 0},
 };
 
@@ -71,6 +72,8 @@ const CrossfireSensor &getCrossfireSensor(uint8_t id, uint8_t subId) {
     return crossfireSensors[ATTITUDE_PITCH_INDEX + subId];
   else if (id == FLIGHT_MODE_ID)
     return crossfireSensors[FLIGHT_MODE_INDEX];
+  else if (id == BARO_ALT_ID)
+    return crossfireSensors[BARO_ALTITUDE_INDEX];
   else
     return crossfireSensors[UNKNOWN_INDEX];
 }
@@ -135,6 +138,21 @@ void processCrossfireTelemetryFrame() {
         processCrossfireTelemetryValue(GPS_SATELLITES_INDEX, value);
       break;
 
+    case BARO_ALT_ID:
+      if (getCrossfireTelemetryValue<2>(3, value)) {
+        if (value & 0x8000) {
+          // Altitude in meters
+          value &= ~(0x8000);
+          value *= 100; // cm
+        } else {
+          // Altitude in decimeters + 10000dm
+          value -= 10000;
+          value *= 10;
+        }
+        processCrossfireTelemetryValue(BARO_ALTITUDE_INDEX, value);
+      }
+      break;
+
     case LINK_ID:
       for (unsigned int i = 0; i <= TX_SNR_INDEX; i++) {
         if (getCrossfireTelemetryValue<1>(3 + i, value)) {

radio/src/telemetry/crossfire.h

@@ -33,6 +33,7 @@
 #define GPS_ID                         0x02
 #define CF_VARIO_ID                    0x07
 #define BATTERY_ID                     0x08
+#define BARO_ALT_ID                    0x09
 #define LINK_ID                        0x14
 #define CHANNELS_ID                    0x16
 #define LINK_RX_ID                     0x1C
@@ -88,6 +89,7 @@ enum CrossfireSensorIndexes {
   ATTITUDE_YAW_INDEX,
   FLIGHT_MODE_INDEX,
   VERTICAL_SPEED_INDEX,
+  BARO_ALTITUDE_INDEX,
   UNKNOWN_INDEX,
 };