FMUv5: Support passive power controls

This ensures that FMU-side power controls are not interfering with IO-side power controls of DSM receivers if they happen to be OR-ed in the schematics

boards/px4/fmu-v5/src/board_config.h

@@ -264,6 +264,7 @@
 #define GPIO_nVDD_5V_HIPOWER_EN         /* PF12 */ (GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_SET|GPIO_PORTF|GPIO_PIN12)
 #define GPIO_nVDD_5V_HIPOWER_OC         /* PG13 */ (GPIO_INPUT |GPIO_FLOAT|GPIO_PORTF|GPIO_PIN13)
 #define GPIO_VDD_3V3_SPEKTRUM_POWER_EN  /* PE4  */ (GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTE|GPIO_PIN4)
+#define GPIO_VDD_3V3_SPEKTRUM_PASSIVE   /* PE4  */ (GPIO_INPUT|GPIO_PULLUP|GPIO_PORTE|GPIO_PIN4)
 #define GPIO_VDD_5V_RC_EN               /* PG5  */ (GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTG|GPIO_PIN5)
 #define GPIO_VDD_5V_WIFI_EN             /* PG6  */ (GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTG|GPIO_PIN5)
 #define GPIO_VDD_3V3_SD_CARD_EN         /* PG7  */ (GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTG|GPIO_PIN7)
@@ -350,6 +351,8 @@
 /* Power switch controls ******************************************************/
 
 #define SPEKTRUM_POWER(_on_true)           VDD_3V3_SPEKTRUM_POWER_EN(_on_true)
+#define SPEKTRUM_POWER_PASSIVE()           px4_arch_configgpio(GPIO_VDD_3V3_SPEKTRUM_PASSIVE)
+#define SPEKTRUM_POWER_CONFIG()           px4_arch_configgpio(GPIO_VDD_3V3_SPEKTRUM_POWER_EN)
 
 /*
  * FMUv5 has a separate RC_IN

boards/px4/fmu-v5/src/init.c

@@ -211,6 +211,15 @@ __EXPORT int board_app_initialize(uintptr_t arg)
 	VDD_5V_PERIPH_EN(true);
 	VDD_5V_HIPOWER_EN(true);
 	board_control_spi_sensors_power(true, 0xffff);
+#ifdef SPEKTRUM_POWER_PASSIVE
+	// Turn power controls to passive
+	SPEKTRUM_POWER_PASSIVE();
+#endif
+	// TODO Historically Spektrum power defaulted to on
+	// newer board configurations should support enabling
+	// power once the RC interface gets switched on instead
+	// the unconditional power-on in the line below is
+	// kept in place for consistency.
 	VDD_3V3_SPEKTRUM_POWER_EN(true);
 	VDD_5V_RC_EN(true);
 	VDD_5V_WIFI_EN(true);