Airmode - Add airmode parameter for multicopter mixer

src/modules/mc_att_control/mc_att_control_params.c

@@ -542,4 +542,18 @@ PARAM_DEFINE_FLOAT(MC_TPA_RATE_D, 0.0f);
  * @increment 10
  * @group Multicopter Attitude Control
  */
-PARAM_DEFINE_FLOAT(MC_DTERM_CUTOFF, 30.f);
+PARAM_DEFINE_FLOAT(MC_DTERM_CUTOFF, 0.f);
+
+/**
+ * Multicopter air-mode
+ *
+ * The air-mode enables the mixer to increase or decrease the total thrust of the multirotor
+ * in order to keep attitude and rate control even at low and high throttle.
+ * This function should be disabled during tuning as it will help the controller
+ * to diverge if the closed-loop is unstable.
+ *
+ * @boolean
+ * @group Multicopter Attitude Control
+ */
+PARAM_DEFINE_INT32(MC_AIRMODE, 0);
+

src/modules/px4iofirmware/mixer.cpp

@@ -254,6 +254,11 @@ mixer_tick(void)
 	 */
 	mixer_group.set_trims(r_page_servo_control_trim, PX4IO_SERVO_COUNT);
 
+	/*
+	 * Update air-mode parameter
+	 */
+	mixer_group.set_airmode(REG_TO_BOOL(r_setup_airmode));
+
 
 	/*
 	 * Run the mixers.

src/modules/px4iofirmware/protocol.h

@@ -78,6 +78,8 @@
 #define REG_TO_FLOAT(_reg)	((float)REG_TO_SIGNED(_reg) / 10000.0f)
 #define FLOAT_TO_REG(_float)	SIGNED_TO_REG((int16_t)floorf((_float + 0.00005f) * 10000.0f))
 
+#define REG_TO_BOOL(_reg) 	((bool)(_reg))
+
 #define PX4IO_PROTOCOL_VERSION		4
 
 /* maximum allowable sizes on this protocol version */
@@ -232,6 +234,8 @@ enum {							/* DSM bind states */
 
 #define PX4IO_P_SETUP_MOTOR_SLEW_MAX		24 	/* max motor slew rate */
 
+#define PX4IO_P_SETUP_AIRMODE 			27 	/* air-mode */
+
 #define PX4IO_P_SETUP_THR_MDL_FAC 		25	/* factor for modelling static pwm output to thrust relationship */
 
 #define PX4IO_P_SETUP_THERMAL			26	/* thermal management */

src/modules/px4iofirmware/px4io.h

@@ -132,6 +132,7 @@ extern uint16_t			r_page_servo_disarmed[];	/* PX4IO_PAGE_DISARMED_PWM */
 #define r_setup_sbus_rate	r_page_setup[PX4IO_P_SETUP_SBUS_RATE]
 #define r_setup_thr_fac		r_page_setup[PX4IO_P_SETUP_THR_MDL_FAC]
 #define r_setup_slew_max	r_page_setup[PX4IO_P_SETUP_MOTOR_SLEW_MAX]
+#define r_setup_airmode		r_page_setup[PX4IO_P_SETUP_AIRMODE]
 
 #define r_control_values	(&r_page_controls[0])
 

src/modules/px4iofirmware/registers.c

@@ -178,6 +178,7 @@ volatile uint16_t	r_page_setup[] = {
 	[PX4IO_P_SETUP_SCALE_PITCH] = 10000,
 	[PX4IO_P_SETUP_SCALE_YAW] = 10000,
 	[PX4IO_P_SETUP_MOTOR_SLEW_MAX] = 0,
+	[PX4IO_P_SETUP_AIRMODE] = 0,
 	[PX4IO_P_SETUP_THR_MDL_FAC] = 0,
 	[PX4IO_P_SETUP_THERMAL] = PX4IO_THERMAL_IGNORE
 };
@@ -704,6 +705,10 @@ registers_set_one(uint8_t page, uint8_t offset, uint16_t value)
 			sbus1_set_output_rate_hz(value);
 			break;
 
+		case PX4IO_P_SETUP_AIRMODE:
+			r_page_setup[PX4IO_P_SETUP_AIRMODE] = value;
+			break;
+
 		case PX4IO_P_SETUP_THR_MDL_FAC:
 			update_mc_thrust_param = true;
 			r_page_setup[offset] = value;