Enable using the 'heading' field in MAVlink to display mAh used

src/main/interface/settings.c

@@ -885,6 +885,12 @@ const clivalue_t valueTable[] = {
 #if defined(USE_TELEMETRY_SMARTPORT)
     { "smartport_use_extra_sensors", VAR_UINT8 | MASTER_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_OFF_ON }, PG_TELEMETRY_CONFIG, offsetof(telemetryConfig_t, smartport_use_extra_sensors)},
 #endif
+#ifdef USE_TELEMETRY_MAVLINK
+    // Support for misusing the heading field in MAVlink to indicate mAh drawn for Connex Prosight OSD
+    // Set to 10 to show a tenth of your capacity drawn.
+    // Set to $size_of_battery to get a percentage of battery used.
+    { "mavlink_mah_as_heading_divisor", VAR_UINT16 | MASTER_VALUE, .config.minmax = { 0, 30000 }, PG_TELEMETRY_CONFIG, offsetof(telemetryConfig_t, mavlink_mah_as_heading_divisor) },
+#endif
 #endif // USE_TELEMETRY
 
 // PG_LED_STRIP_CONFIG

src/main/telemetry/mavlink.c

@@ -136,6 +136,17 @@ static void mavlinkSerialWrite(uint8_t * buf, uint16_t length)
         serialWrite(mavlinkPort, buf[i]);
 }
 
+static int16_t headingOrScaledMilliAmpereHoursDrawn(void)
+{
+    if (isAmperageConfigured() && telemetryConfig()->mavlink_mah_as_heading_divisor > 0) {
+        // In the Connex Prosight OSD, this goes between 0 and 999, so it will need to be scaled in that range.
+        return getMAhDrawn() / telemetryConfig()->mavlink_mah_as_heading_divisor;
+    }
+    // heading Current heading in degrees, in compass units (0..360, 0=north)
+    return DECIDEGREES_TO_DEGREES(attitude.values.yaw);
+}
+
+
 void freeMAVLinkTelemetryPort(void)
 {
     closeSerialPort(mavlinkPort);
@@ -354,7 +365,7 @@ void mavlinkSendPosition(void)
         // Ground Z Speed (Altitude), expressed as m/s * 100
         0,
         // heading Current heading in degrees, in compass units (0..360, 0=north)
-        DECIDEGREES_TO_DEGREES(attitude.values.yaw)
+        headingOrScaledMilliAmpereHoursDrawn()
     );
     msgLength = mavlink_msg_to_send_buffer(mavBuffer, &mavMsg);
     mavlinkSerialWrite(mavBuffer, msgLength);
@@ -433,7 +444,7 @@ void mavlinkSendHUDAndHeartbeat(void)
         // groundspeed Current ground speed in m/s
         mavGroundSpeed,
         // heading Current heading in degrees, in compass units (0..360, 0=north)
-        DECIDEGREES_TO_DEGREES(attitude.values.yaw),
+        headingOrScaledMilliAmpereHoursDrawn(),
         // throttle Current throttle setting in integer percent, 0 to 100
         scaleRange(constrain(rcData[THROTTLE], PWM_RANGE_MIN, PWM_RANGE_MAX), PWM_RANGE_MIN, PWM_RANGE_MAX, 0, 100),
         // alt Current altitude (MSL), in meters, if we have sonar or baro use them, otherwise use GPS (less accurate)

src/main/telemetry/telemetry.c

@@ -77,6 +77,7 @@ PG_RESET_TEMPLATE(telemetryConfig_t, telemetryConfig,
             IBUS_SENSOR_TYPE_EXTERNAL_VOLTAGE
     },
     .smartport_use_extra_sensors = false,
+    .mavlink_mah_as_heading_divisor = 0,
 );
 
 void telemetryInit(void)

src/main/telemetry/telemetry.h

@@ -54,6 +54,7 @@ typedef struct telemetryConfig_s {
     uint8_t report_cell_voltage;
     uint8_t flysky_sensors[IBUS_SENSOR_COUNT];
     uint8_t smartport_use_extra_sensors;
+    uint16_t mavlink_mah_as_heading_divisor;
 } telemetryConfig_t;
 
 PG_DECLARE(telemetryConfig_t, telemetryConfig);