Change airmode activation to be throttle percent based to fix 3D mode

The previous logic used an absolute throttle value of 1350us which won't work in 3D mode and resulted in airmode being activated on arming.  Renamed the parameter to airmode_start_throttle_percent and set the default to 32 (equivalent to what the previous setting of 1350 when min_check is taken into account).

To preserve MSP functionality the value is transformed to/from microsecond values (32 becomes 1320) when interfaced.

src/main/fc/fc_core.c

@@ -97,8 +97,6 @@ enum {
 
 #define GYRO_WATCHDOG_DELAY 80 //  delay for gyro sync
 
-#define AIRMODE_THOTTLE_THRESHOLD 1350 // Make configurable in the future. ~35% throttle should be fine
-
 #ifdef USE_RUNAWAY_TAKEOFF
 #define RUNAWAY_TAKEOFF_DEACTIVATE_STICK_PERCENT 15   // 15% - minimum stick deflection during deactivation phase
 #define RUNAWAY_TAKEOFF_DEACTIVATE_PIDSUM_LIMIT  100  // 10.0% - pidSum limit during deactivation phase
@@ -446,6 +444,7 @@ bool areSticksActive(uint8_t stickPercentLimit)
     }
     return false;
 }
+#endif
 
 
 // calculate the throttle stick percent - integer math is good enough here.
@@ -470,7 +469,7 @@ uint8_t calculateThrottlePercent(void)
     }
     return ret;
 }
-#endif
+
 
 /*
  * processRx called from taskUpdateRxMain
@@ -498,9 +497,10 @@ bool processRx(timeUs_t currentTimeUs)
     failsafeUpdateState();
 
     const throttleStatus_e throttleStatus = calculateThrottleStatus();
+    const uint8_t throttlePercent = calculateThrottlePercent();
 
     if (isAirmodeActive() && ARMING_FLAG(ARMED)) {
-        if (rcData[THROTTLE] >= rxConfig()->airModeActivateThreshold) {
+        if (throttlePercent >= rxConfig()->airModeActivateThreshold) {
             airmodeIsActivated = true; // Prevent Iterm from being reset
         }
     } else {
@@ -538,7 +538,7 @@ bool processRx(timeUs_t currentTimeUs)
         //   - pidSum on all axis is less then runaway_takeoff_deactivate_pidlimit
         bool inStableFlight = false;
         if (!feature(FEATURE_MOTOR_STOP) || isAirmodeActive() || (throttleStatus != THROTTLE_LOW)) { // are motors running?
-            if ((calculateThrottlePercent() >= pidConfig()->runaway_takeoff_deactivate_throttle)
+            if ((throttlePercent >= pidConfig()->runaway_takeoff_deactivate_throttle)
                 && areSticksActive(RUNAWAY_TAKEOFF_DEACTIVATE_STICK_PERCENT)
                 && (fabsf(axisPIDSum[FD_PITCH]) < RUNAWAY_TAKEOFF_DEACTIVATE_PIDSUM_LIMIT)
                 && (fabsf(axisPIDSum[FD_ROLL]) < RUNAWAY_TAKEOFF_DEACTIVATE_PIDSUM_LIMIT)

src/main/interface/msp.c

@@ -1013,7 +1013,7 @@ static bool mspProcessOutCommand(uint8_t cmdMSP, sbuf_t *dst)
         sbufWriteU16(dst, rxConfig()->rx_max_usec);
         sbufWriteU8(dst, rxConfig()->rcInterpolation);
         sbufWriteU8(dst, rxConfig()->rcInterpolationInterval);
-        sbufWriteU16(dst, rxConfig()->airModeActivateThreshold);
+        sbufWriteU16(dst, (rxConfig()->airModeActivateThreshold * 10) + 1000);
         sbufWriteU8(dst, rxConfig()->rx_spi_protocol);
         sbufWriteU32(dst, rxConfig()->rx_spi_id);
         sbufWriteU8(dst, rxConfig()->rx_spi_rf_channel_count);
@@ -1872,7 +1872,7 @@ static mspResult_e mspProcessInCommand(uint8_t cmdMSP, sbuf_t *src)
         if (sbufBytesRemaining(src) >= 4) {
             rxConfigMutable()->rcInterpolation = sbufReadU8(src);
             rxConfigMutable()->rcInterpolationInterval = sbufReadU8(src);
-            rxConfigMutable()->airModeActivateThreshold = sbufReadU16(src);
+            rxConfigMutable()->airModeActivateThreshold = ((sbufReadU16(src) - 1000) / 10);
         }
         if (sbufBytesRemaining(src) >= 6) {
             rxConfigMutable()->rx_spi_protocol = sbufReadU8(src);

src/main/interface/settings.c

@@ -421,7 +421,7 @@ const clivalue_t valueTable[] = {
     { "spektrum_sat_bind",          VAR_UINT8  | MASTER_VALUE, .config.minmax = { SPEKTRUM_SAT_BIND_DISABLED, SPEKTRUM_SAT_BIND_MAX}, PG_RX_CONFIG, offsetof(rxConfig_t, spektrum_sat_bind) },
     { "spektrum_sat_bind_autoreset",VAR_UINT8  | MASTER_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_OFF_ON }, PG_RX_CONFIG, offsetof(rxConfig_t, spektrum_sat_bind_autoreset) },
 #endif
-    { "airmode_start_throttle",     VAR_UINT16 | MASTER_VALUE, .config.minmax = { 1000, 2000 }, PG_RX_CONFIG, offsetof(rxConfig_t, airModeActivateThreshold) },
+    { "airmode_start_throttle_percent",     VAR_UINT8 | MASTER_VALUE, .config.minmax = { 0, 100 }, PG_RX_CONFIG, offsetof(rxConfig_t, airModeActivateThreshold) },
     { "rx_min_usec",                VAR_UINT16 | MASTER_VALUE, .config.minmax = { PWM_PULSE_MIN, PWM_PULSE_MAX }, PG_RX_CONFIG, offsetof(rxConfig_t, rx_min_usec) },
     { "rx_max_usec",                VAR_UINT16 | MASTER_VALUE, .config.minmax = { PWM_PULSE_MIN, PWM_PULSE_MAX }, PG_RX_CONFIG, offsetof(rxConfig_t, rx_max_usec) },
     { "serialrx_halfduplex",        VAR_UINT8  | MASTER_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_OFF_ON }, PG_RX_CONFIG, offsetof(rxConfig_t, halfDuplex) },

src/main/rx/rx.c

@@ -150,7 +150,7 @@ void pgResetFn_rxConfig(rxConfig_t *rxConfig)
         .rcInterpolationChannels = 0,
         .rcInterpolationInterval = 19,
         .fpvCamAngleDegrees = 0,
-        .airModeActivateThreshold = 1350,
+        .airModeActivateThreshold = 32,
         .max_aux_channel = DEFAULT_AUX_CHANNEL_COUNT
     );
 

src/main/rx/rx.h

@@ -139,7 +139,7 @@ typedef struct rxConfig_s {
     uint8_t rcInterpolationChannels;
     uint8_t rcInterpolationInterval;
     uint8_t fpvCamAngleDegrees;             // Camera angle to be scaled into rc commands
-    uint16_t airModeActivateThreshold;      // Throttle setpoint where airmode gets activated
+    uint8_t airModeActivateThreshold;       // Throttle setpoint percent where airmode gets activated
 
     uint16_t rx_min_usec;
     uint16_t rx_max_usec;