arduino-coldfire-bdm

An interface to Motorola® Coldfire processors' Background Debug Interface (BDM) using an Arduino.

pip install arduino-coldfire-bdm

Usage

1. Ensure you have a working Python 3 installation.
2. Run pip install arduino-coldfire-bdm on the command line to install this package.
3. Connect an Arduino to a Motorola Coldfire via its debug pins. See arduino-coldfire-bdm.ino for suggested pin mappings. (Ensure the Coldfire board is powered up independently; the Arduino does not supply power to the Coldfire.)
4. Use the Arduino IDE to compile and upload arduino-coldfire-bdm.ino to your Arduino.
   • Note that you may need to change the pin numbers at the top of the script depending on your Arduino and the pins you used to connect to the Coldfire.
5. On the command line (Terminal.app, Command Prompt on Windows, etc), run arduino-coldfire-bdm (or, if that doesn't work, python3 -m arduino_coldfire_bdm.command_line) to invoke the command line program. You should see the following help text:

usage: arduino-coldfire-bdm [-h] [--dry-run] [--show-commands] [--serial-port SERIAL_PORT] [--baud-rate BAUD_RATE] {dump_memory,trace_execution,load_flash,sram_test} ...

Communicate with an attached Coldfire V3 board (and maybe other versions too) to act as a simple debugger, via an Arduino serial connection.

options:
  -h, --help            show this help message and exit
  --dry-run             If passed, don't actually connect to a serial port; just queue up commands that would have otherwise been sent to an attached Arduino.
  --show-commands       If passed, print out a listing of every command sent to the Arduino.
  --serial-port SERIAL_PORT
                        The file path of the serial port to connect to.
  --baud-rate BAUD_RATE
                        The baud rate to use when connecting to the Arduino over serial. Must match what the Arduino expects.

commands:
  {dump_memory,trace_execution,load_flash,sram_test}
    dump_memory         Dump memory.
    trace_execution     Begin execution and print out the program counter and registers before every instruction.
    load_flash          Erase an attached Flash chip and load in new contents from a file.
    sram_test           Test SRAM attached to the Coldfire. Expects exactly 1MB of RAM, attached via chip-select port 1, mapped at 0x00200000.

6. Select the appropriate --serial-port to use to connect to your Arduino, and run one of the commands.

What?

A long long time ago (the mid-1990s), Motorola created a series of CPUs derived from the 68k architecture, called the Coldfire. These processors are largely obsolete today, but are still found in certain industrial equipment and embedded devices released around that time; including some vintage synthesizers, like the Alesis A6 Andromeda.

This repository contains two things:

• an Arduino sketch, which allows connecting pretty much any Arduino to a Coldfire processor's Background Debug Mode (BDM) port to send and receive data
• a Python library to connect to an Arduino over USB serial, to allow running high-level debugging commands, like:
  • tracing execution (i.e.: like GDB or LLDB)
  • dumping the contents of memory to a file
  • erasing and re-flashing an attached flash memory chip
  • testing attached RAM chips
  • whatever else you want; it's Python! You can script it.

This library, when paired with an Arduino, performs many of the same functions as PEMicro's Multilink debugging probes. This library is free, runs wherever you can run an Arduino and Python code (rather than just on Windows), and requires no drivers. However, this library is way slower, is missing a ton of functions, and has no IDE support.

Why?

I bought a broken Alesis A6 Andromeda, and wanted to try fixing it by re-flashing its firmware without doing any soldering, because I'm bad at soldering. Read about that journey on my blog.

How?

I read the MCF5307 data sheet (484 pages) very carefully. It documents how to connect to a Coldfire BDM port from first principles.

See the top of arduino-coldfire-bdm.ino to figure out which pins to connect between the Arduino and your Coldfire's debug port.

Can I use this for other things?

Probably. There are certain assumptions made (especially around interfacing with Flash or RAM) that apply only to the Andromeda, and may not be useful for other devices. Pull requests to make this code more generic would be welcomed.

What if I brick my device?

Here's the license; I take no responsibility if this software is misused. You should probably read the software carefully first.

Also; I tested this with a 5V Arduino on a 3.3V Coldfire CPU. It seemed to work just fine. That might fry your device; your mileage may vary.

Copyright (c) 2022 Peter Sobot

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"Software"), to deal in the Software without restriction, including
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The above copyright notice and this permission notice shall be
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