ArduBDM

A BDM (Background Debug Mode) adapter for the CPU32 family (MC68332/MC68376) found in SAAB Trionic 5, 7 and 8 ECUs. It runs on an Arduino Nano with the ATmega328PB, bit-bangs the BDM protocol and talks to the host over USB serial. Together with BDMTool it reads, erases and flashes the ECU.

Download firmware · Source on GitHub

Features

Reset into BDM, run, stop and single step the target
Read and write memory and registers
Fast block dumps: a full 512 KB Trionic 7 read takes about 7 seconds
RAM-resident flash drivers for AMD 29Fxxx (Trionic 7/8) and 28F010 (Trionic 5) chips; a full 512 KB erase, write and verify takes about 30 seconds with BDMTool
Simple ASCII serial protocol at 1 Mbaud, easy to script
Target voltage monitoring

Hardware

The PCB is a small hat for the Arduino Nano with a shrouded 2x5 IDC box header for the BDM cable. No other components are needed, the ECU supplies the pull-ups and everything runs at 5 V. The KiCad project is in the repository.

Pinout

10-pin CPU32 BDM header to Arduino pin. The plug goes on 1:1 with the red stripe at pin 1.

BDM pin	Signal	Arduino	Description
1	DS	D8	Not used by CPU32 BDM, wired for other targets
2	BERR	D6	Bus error, input by default
3	GND	GND
4	BKPT/DSCLK	D5	Breakpoint / serial clock
5	GND	GND
6	FREEZE	D4	High when the target is in BDM
7	RESET	D7	Driven low or released, never high
8	IFETCH/DSI	D3	Data to target
9	VDD	A0	Target voltage sense
10	IPIPE/DSO	D2	Data from target

BDM header, top view, pin 1 marked on the ECU board:

 1 DS      2 BERR
 3 GND     4 BKPT/DSCLK
 5 GND     6 FREEZE
 7 RESET   8 DSI
 9 VDD    10 DSO

Flashing the firmware

Build and upload with PlatformIO, or grab a prebuilt hex from the releases page and flash it with avrdude:

avrdude -c arduino -p m328pb -P /dev/ttyUSB0 -b 115200 -U flash:w:ardubdm-vX.hex

Status

Bench verified on Trionic 7 and Trionic 5.5: reading, erasing and flashing full images that match CombiAdapter reads byte for byte. Note that a Trionic 5 needs 14-15 V on the bench when flashing.

If you like the project please donate 💕