Perfect, this is exactly what I was looking for.
@pyrate The pixhawk only comes with the more modern I2C cable - the same as all the other connections. There was no DF13 to the new type. Also the telemetry out in this case wasn't DF13 but another type, I'll pop up a photo when I get a chance.
So knowing the red as positive and black as ground on the telemetry cable I numbered ground as 1, green 2, yellow 3 and positive 4. On the pixhawk 6pin DF13 to new connection, I numbered Ground 1, skipped the one next to ground, then 2, 3, positve 4. Matched these numbers and it worked.