We need to increase the distance between our 3DR Compass/GPS module and the Pixhawk due to magnetic interference from onboard systems (APM:Plane)
When doing this it would be great to reduce the number of wires too, as ground and +5V are common to both but I can’t seem to find the pinouts for the GPS and compass in the wiki to see what wires can be omitted (if any) or duplicated.
Can anyone help?
Ok found them, helps to look properly 
so the question is can 4 & 5 be omitted?
And can GND and +5V be made common for Compass and GPS?
1 (red) VCC +5V
2 (blk) TX (OUT) +3.3V
3 (blk) RX (IN) +3.3V
4 (blk) CAN2 TX +3.3V
5 (blk) CAN2 RX +3.3V
6 (blk) GND GND
Here’s the basic hookup to the apm with diagrams for the uBlox v1.1 and v1.2
viewtopic.php?f=47&t=7759
Hope this helped
First of all, compass is I2C and therefore SCL and SDA. You will need 6 wires. Pos, Neg, Tx, Rx, SCL, SDA. That assumes there is a 3V regulator running the VCC for the compass. I think there is. Btw, you can get this for $34 at infinity hobby. 
Compass VCC is listed as 5V, so I’ve gone and connected it all up and it seems to be good.
Did you run just 6 wires?
If so, compass is getting its VCC of 3.3V from the same regulator that is supplying GPS.
Compass (I2C) is 5V
From the Pixhawk overview:
1 (red) VCC +5V
2 (blk) SCL +3.3 (pullups)
3 (blk) SDA +3.3 (pullups)
4 (blk) GND GND
copter.ardupilot.com/wiki/common … -overview/
I thought ur goal was to reduce wiring?
Compass chip is 3.3v they hav a regulator. This same combo works on APM. The APM I2C is 3.3V
Anyway, if ur happy that’s all that counts. I hav GPS n compass with total of 6 wires. I wouldn’t b surprised if 5v trace is common to GPS n compass. That way they can be used separate or together. See stand alone compass on 3DR site. It has regulator but has to b bridged for either 3.3 or 5v
Am running 6 wires, common +5V & GND, Tx, Rx, SCL, SDA.
The wiki page referred to in my last post clearly states that I2C is 5V, is that incorrect?
[quote=“Graham Dyer”]Am running 6 wires, common +5V & GND, Tx, Rx, SCL, SDA.
The wiki page referred to in my last post clearly states that I2C is 5V, is that incorrect?[/quote]
Yes, for the Pixhawk. APM is 3.3V