A relay's pin cannot be used, or two relays share one pin

What ArduPilot says:

• …=N invalid
• …=N, set SERVON_FUNCTION=-1
• pin conflict RELAYN_PIN = RELAYN_PIN

A relay is a pin ArduPilot switches on and off (a camera shutter, a parachute, lights). Each enabled relay (RELAYn_FUNCTION not 0) with a pin is checked. “RELAY2_PIN=54 invalid”: this board has no GPIO (a general-purpose pin) with that number. “set SERVOn_FUNCTION=-1”: the pin is a servo/motor output that still works as an output. “pin conflict RELAY1_PIN = RELAY3_PIN”: two enabled relays name the same pin.

What to do, most likely first

1. The pin is one of the servo/motor outputs and has not been turned into a GPIO.

   CheckThe message names the output: “set SERVO9_FUNCTION=-1” is output 9.

   FixSet that SERVOn_FUNCTION to -1 (GPIO) and reboot: outputs become GPIO pins only at start-up. Nothing else (a motor, a servo) may be wired to that output.

2. No relay is used: an old relay pin was turned into an enabled relay by the upgrade to 4.5 or later, or the setting came from another aircraft's file.

   FixSet RELAYn_FUNCTION to 0 for every relay you do not use.

3. The pin number belongs to another board.

   FixSet RELAYn_PIN to a GPIO number from your own board's ArduPilot documentation page.

4. Two relays were given the same pin.

   CheckThe message names the two relays; compare their RELAYn_PIN values.

   FixGive each relay its own pin, or set the extra relay's RELAYn_FUNCTION to 0.

Parameters to look at

Where to do it:Board & Wiring PlannerParameter Compare & Migrate