which is connect to an RC radio on which I have a free channel.
program on the Uno in mid-flight
Quotewhich is connect to an RC radio on which I have a free channel.Does this mean a free servo channel or is there a data channel? Or do you want to program via the autopilot?
Quoteprogram on the Uno in mid-flightI hope its functions aren't mission critical
The receiver is fully connected to the Ardupilot with a spare channel to play with.
I would like to somehow change how the LEDs are behaving
QuoteThe receiver is fully connected to the Ardupilot with a spare channel to play with. I've not used these bits, what exactly is the has a spare RC channel got to do with the Arduino hanging off the Ardupilot?If it's just an RC channel I don't see how it's of any use for "talking" to the Arduino except in the most simple of ways. Certainly not for reprogramming. That said
QuoteI would like to somehow change how the LEDs are behavingYou don't have to "reprogram" the Arduino to do this, just write a program that accepts some data from the Ardupilot and drives the LEDs differently according to the data.That should be possible using an RC channel. Do I have this right?RC channel ---> Ardupilot ----> ArduinoIf so what do you get into the Arduino? Pulse train, SPI data, something else?
I think you said that this channel is controlled by a switch on the transmitter, how many positions on this switch? That will determine how many different "programs" you can run.