is there a solder jumper to tell the main board to use the external GPS port?
You can buy it in a version with external GPS. Just chose "none" for GPS in the product listing:
i bought the one with the onboard GPS but depending where i am mounting it i might half to use the external GPS that i also bought at the same time... what i need to know is how to tell the APM 2.0 main board what GPS i want to use
Does this exist yet?