RSSI and concurrent S.Bus output handling

src/modules/px4iofirmware/controls.c

@@ -114,9 +114,18 @@ controls_tick() {
 
 	perf_begin(c_gather_sbus);
 	bool sbus_updated = sbus_input(r_raw_rc_values, &r_raw_rc_count, &rssi, PX4IO_RC_INPUT_CHANNELS);
+
+	bool sbus_status = (r_status_flags & PX4IO_P_STATUS_FLAGS_RC_SBUS);
+
 	if (sbus_updated) {
 		r_status_flags |= PX4IO_P_STATUS_FLAGS_RC_SBUS;
 	}
+
+	/* switch S.Bus output pin as needed */
+	if (sbus_status != (r_status_flags & PX4IO_P_STATUS_FLAGS_RC_SBUS)) {
+		ENABLE_SBUS_OUT((r_status_flags & PX4IO_P_STATUS_FLAGS_RC_SBUS));
+	}
+
 	perf_end(c_gather_sbus);
 
 	/*

src/modules/px4iofirmware/px4io.c

@@ -196,6 +196,11 @@ user_start(int argc, char *argv[])
 	POWER_SERVO(true);
 #endif
 
+	/* turn off S.Bus out (if supported) */
+#ifdef ENABLE_SBUS_OUT
+	ENABLE_SBUS_OUT(false);
+#endif
+
 	/* start the safety switch handler */
 	safety_init();
 

src/modules/px4iofirmware/px4io.h

@@ -160,6 +160,7 @@ extern pwm_limit_t pwm_limit;
 
 # define PX4IO_RELAY_CHANNELS		0
 # define POWER_SPEKTRUM(_s)		stm32_gpiowrite(GPIO_SPEKTRUM_PWR_EN, (_s))
+# define ENABLE_SBUS_OUT(_s)		stm32_gpiowrite(GPIO_SBUS_OENABLE, (_s))
 
 # define VDD_SERVO_FAULT		(!stm32_gpioread(GPIO_SERVO_FAULT_DETECT))