Project Fiero 2003 - Door Control Module

by Oliver Scholz

Introduction

I based the Door Control Module (DCM) on my Power Window Controller, but with smarter signal processing, and capabilities to control the entire door:

• Power door switches
• Door ajar switch
• Door jamb switch
• Outside temperature sensor
• Power door lock motor
• Power window motor control
• Mirror motor control
• Mirror heater
• Puddle light

The door controle module is based on the Motorola MC68HC912B32 which is readily available, and has a BDLC (J1850 module) on chip.

J1850 handler

The biggest challenge was developing a J1850 handler for the B32 from scratch. This is where the protocol bridge came in handy, and I found two bugs in the bridge in the process. I was able to port the message transmission and receive routines from the bridge, but decoding the functional and physical messages was, though not really difficult, a pain. At this point the physical message handler is 95% complete and functional, with the exception of memory modification routines. The functional messages are being implemented as work on the remaining modules progresses.

LIN handler

Motorola has a LIN master implementation on their website for download, which I used as a starting point. Unfortunately they only provide a lib for linking, so I can not really debug into the LIN handler. Communication with the CCM seems to be working though.

What's next?

With both communication handlers out of the way, implementation like reading temperature or setting the IP illumination on the CCM through the J1850 bus was easy. Next on the list are interpreting the switch messages from the CCM and controlling the mirror motors, door locks and lock motors. Stay tuned for new developments on this project...