IO firmware: Support pwm reversal

src/modules/px4iofirmware/mixer.cpp

@@ -234,7 +234,7 @@ mixer_tick(void)
 		in_mixer = false;
 
 		/* the pwm limit call takes care of out of band errors */
-		pwm_limit_calc(should_arm, mixed, r_page_servo_disarmed, r_page_servo_control_min, r_page_servo_control_max, outputs, r_page_servos, &pwm_limit);
+		pwm_limit_calc(should_arm, mixed, r_setup_pwm_reverse, r_page_servo_disarmed, r_page_servo_control_min, r_page_servo_control_max, outputs, r_page_servos, &pwm_limit);
 
 		for (unsigned i = mixed; i < PX4IO_SERVO_COUNT; i++)
 			r_page_servos[i] = 0;
@@ -272,8 +272,9 @@ mixer_tick(void)
 
 	if (mixer_servos_armed && should_arm) {
 		/* update the servo outputs. */
-		for (unsigned i = 0; i < PX4IO_SERVO_COUNT; i++)
+		for (unsigned i = 0; i < PX4IO_SERVO_COUNT; i++) {
 			up_pwm_servo_set(i, r_page_servos[i]);
+		}
 
 		/* set S.BUS1 or S.BUS2 outputs */
 

src/modules/px4iofirmware/protocol.h

@@ -233,6 +233,8 @@ enum {							/* DSM bind states */
 #define PX4IO_P_SETUP_FORCE_SAFETY_ON		14	/* force safety switch into 'disarmed' (PWM disabled state) */
 #define PX4IO_FORCE_SAFETY_MAGIC		22027	/* required argument for force safety (random) */
 
+#define PX4IO_P_SETUP_PWM_REVERSE		15	/**< Bitmask to reverse PWM channels 1-8 */
+
 /* autopilot control values, -10000..10000 */
 #define PX4IO_PAGE_CONTROLS			51	/**< actuator control groups, one after the other, 8 wide */
 #define PX4IO_P_CONTROLS_GROUP_0		(PX4IO_PROTOCOL_MAX_CONTROL_COUNT * 0)	/**< 0..PX4IO_PROTOCOL_MAX_CONTROL_COUNT - 1 */

src/modules/px4iofirmware/px4io.h

@@ -111,6 +111,8 @@ extern uint16_t			r_page_servo_disarmed[];	/* PX4IO_PAGE_DISARMED_PWM */
 #endif
 #define r_setup_rc_thr_failsafe	r_page_setup[PX4IO_P_SETUP_RC_THR_FAILSAFE_US]
 
+#define r_setup_pwm_reverse	r_page_setup[PX4IO_P_SETUP_PWM_REVERSE]
+
 #define r_control_values	(&r_page_controls[0])
 
 /*

src/modules/px4iofirmware/registers.c

@@ -173,6 +173,7 @@ volatile uint16_t	r_page_setup[] =
 	[PX4IO_P_SETUP_REBOOT_BL]		= 0,
 	[PX4IO_P_SETUP_CRC ... (PX4IO_P_SETUP_CRC+1)] = 0,
 	[PX4IO_P_SETUP_RC_THR_FAILSAFE_US] = 0,
+	[PX4IO_P_SETUP_PWM_REVERSE] = 0,
 };
 
 #ifdef CONFIG_ARCH_BOARD_PX4IO_V2
@@ -622,6 +623,10 @@ registers_set_one(uint8_t page, uint8_t offset, uint16_t value)
 			}
 			break;
 
+		case PX4IO_P_SETUP_PWM_REVERSE:
+			r_page_setup[PX4IO_P_SETUP_PWM_REVERSE] = value;
+			break;
+
 		default:
 			return -1;
 		}