The OBDLink SX is an inexpensive USB OBDII scantool marketed by ScanTool.net. It’s sold as a Windows-only scantool and comes packaged with some very simple OBDII software.
Not much exists on MacOS X for CAN monitoring, but I was still curious if I could access my car through my Mac. The System Information app told me the OBDLink SX had the vendor ID for Future Technology Devices International, a manufacturer of popular USB<->Serial bridges like the ones in the Beaglebone Black. Once I had that established it was just a matter of guessing the baud rate to see what was connected to it, and a few minutes later I discovered the OBDLink SX is actually the common ELM327 OBD to RS232 Interpreter, for which a great deal of software already exists.
So here’s how you can chat with the OBDLink SX USB on MacOS X:
- Connect the OBDLink and check if the device appears at /dev/tty.usbserial-000012FD. The Console will also say FTDIUSBSerialDriver: start - ok. If you don’t see the device or this message then you may need to install the FTDI USB kext from here or here.
- Open a screen session 115200 baud, 8 bits, no stop bits, parity.
- Type ATZ <enter> to reset the device, at which point you can chat with it.
- If you want to be able to see what it’s saying back send the ATL1 command to enable line feeds.
$ screen /dev/tty.usbserial-000012FD 115200,cs8,-cstopb,parity > ATZ ELM327 v1.3a > ATL1 OK >AT@1 SCANTOOL.NET LLC