Here’s something a little different! At the end of last week, one of our customers delivered a small scissor lift machine for me to work on – lucky we have lots of space in our garage! I’ve avoided unpacking it as far as possible, because it will soon have to ship back again!
Our customer wants us to adapt our CANbus Display Module to work on this machine. It will be installed in this platform box, connecting to the operator joystick and controlling the three buttons and display to replace what’s there already, so first, I need to open up this platform box and see what is in there already; we already know that communications between this platform box and the vehicles motor controller uses the CANbus protocol, and a quick overview inside the platform box identifies the electronics that’s currently doing that job:
The bottom connector, just visible in that picture, has the CANbus signals as well as power; there’s also an added on terminator resistor (the little component at the bottom with red and brown stripes), which makes my job really easy!
Since the CANbus protocol is somewhat of a standard, it’s not too tricky to figure out what messages the original electronics are sending – my Agilent oscilloscope can convert the voltages to data so I mostly just figure out how the data changes when I action the platform box controls …
After that, I wire up a new connector to “steal” the vehicles CANbus and power, and adapt it to my CANbus display module bench test unit (I can’t cut or splice any wires, since the vehicle will be returned soon):
It’s just an hour or so of coding and testing to rewrite our standard CANbus messages to duplicate those of the vehicle, and then I’m up and running, able to control the vehicle movements from my bench rig!
My colleagues back in Essex will now build a CANbus display into a second platform box that we’ve been supplied, and once I confirm it’s working fine, we are done.
M&I / GBMINI 
