Yet another car related project, this is the AVR J1850 VPW Interface which was designed as an On Board Diagnostic tool for car monitoring. The brain of the device is again the ATmega8 AVR microcontroller from Atmel, with 8KB of flash memory (this is more than enough for all kinds of features, since the basic source code is only 3KB).
The device supports serial RS232 for connection with the automobile, different baud rates (varying from 9600 to 115200 Baud), 4 different bus monitor functions and can handle header messages of 1 and 3 Bytes long. The circuit was designed for a single layer PCB and, starting with firmware 1.04, the device has a crystal 7.3728MHz. The controller is programmed using the ISP connector.
The interface has been tested with various ODB software, including Scantool.net, wOBD, Scanmaster and many more. A .pdf file containing the schematic, parts list, bill of material and other information regarding this project is available in the link below, as well as the source code, released under GPL.
AVR J1850 VPW Interface: [Link]