I was looking at something similar a while ago for supplemental instrumentation. Never got very far and I've changed cars twice since then.
From what I remember most of those Bluetooth/USB OBD gadgets use the elm327 or a copy of it. That's an OBD to UART IC and last I looked was available in single quantities direct from the manufacturer. They were helpful when I asked about interfacing it to a Pi (it's a 5v device not a 3.3v one).
The tricky bit with rolling your own from scratch is that while the connector is standardised, as is which pins are used for which interface the actual presence of a particular interface is not. Neither are most of the potential messages.
IIRC there are about four different interfaces (including CAN) but not all interfaces are present on all cars. The elm327 and clones should take care of that for you though.
Can't help with android auto though. Sorry.
From what I remember most of those Bluetooth/USB OBD gadgets use the elm327 or a copy of it. That's an OBD to UART IC and last I looked was available in single quantities direct from the manufacturer. They were helpful when I asked about interfacing it to a Pi (it's a 5v device not a 3.3v one).
The tricky bit with rolling your own from scratch is that while the connector is standardised, as is which pins are used for which interface the actual presence of a particular interface is not. Neither are most of the potential messages.
IIRC there are about four different interfaces (including CAN) but not all interfaces are present on all cars. The elm327 and clones should take care of that for you though.
Can't help with android auto though. Sorry.
Statistics: Posted by thagrol — Sat Jul 12, 2025 2:45 pm