Nice Gadgets
These days OBD diagnostic chips are based increasingly on CAN-capable processor platforms and can exchange data in various ways via protocol scan. The diagnostic chip ‘pings’ protocols sequentially and links up with the engine management system once the correct protocol has been recognised. The 8-bit PIC or AVR controller used as the hardware platform does, however, require rather a lot of additional hardware to meet the demands of all the multiple protocols. This makes the time ripe for a more efficient solution using a modern controller and this was the motivation for developing the Diamex DXM module, which is used in our OBD2 Analyser NG.
The DXM module comprises an ARM Cortex M3 controller and the necessary surfacemount device (SMD) circuitry on a small printed circuit board (PCB). This module reduces external circuitry requirements to a minimum and offers a unified yet versatile hardware basis for developing compact OBD2 projects. Designed as a universal OBD2 diagnostics and control unit with its own dedicated firmware, it can be connected direct to a vehicle’s diagnostics port. A high-speed (up to 250,000 Baud) serial interface provides an external connection. At the heart of the module is the 32-bit ARM Cortex M3 CPU with a clock frequency of 72 MHz, 64 KB of flash memory and 20 KB of RAM. The environment comprises a K line protection IC, a CAN driver, MOS transistors for the PWM-based protocols, two signal lines and a dedicated power supply with over-voltage protection.