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In my last post I showed a Flip32 flight controller talking to a PX4Flow unit using the I^2C protocol.  Once that was working, I wanted to mount the PX4Flow to a vehicle and make a more permanent cable connection.

For the mount, I used Tinkercad to design a simple rectangular plate with four recessed screw holes, plus a small rectangular hole to pass the I^2C cable through.  Four M3 nylon machine screws and standoffs, both 5mm size, fit snugly into the holes, after which I mounted the plate permanently on the rear  bottom plate of my 250mm H-quad using E6000 adhesive.  

To make the cable, I soldered one end of the four-position cable from 3R to a four-pin jumper cable from Sparkfun.  To keep the color-coding sensible, I covered the red jumper wire with black heat-shrink tubing, making it the ground (leftmost) of the four I^2C pins on the Flip32.  Then the orange wire was +5V, the yellow SCL, and the green SDA:

Once the PX4Flow unit was mounted and wired, I found that the vehicle's legs were too short.  So I designed and printed some extra-long legs, allowing the unit plenty of ground clearance:

My ultimate goal is to modify the Flip32's Baseflight firmware so it uses the sonar and optical-flow readings from the PX4Flow to perform altitude- and position-hold.  Before doing that, I plan to collect in-flight data from the PX4Flow, by attaching a Bluesmirf modem to the Flip32's UART pins and sending a new MSP message from the Flip32 to a Python program on my laptop.