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Here's a brief guide on how to connect a BDM interface to a Trionic7 ECU.

BDM (stands for Background Debug Mode) is an electronic interface for debugging microcontrollers and other embedded systems. It allows direct access to circuit components. In our case, we will be using it to overwrite the flash memory on the Trionic ECU. Normally, connecting via the CAN bus is a more convenient way to flash it, but if that process fails, you end up with a dead ECU. The only way to revive it is by attaching a BDM controller. Guess what happened to me ;].

Related Links: ECUProject forums, T7Suite, T7Tool and BDM utilities, BD32 How-To.


There's a variety of BDM interfaces available on the market. However, this one proved to be most reliable and cost effective. It looks like it's made in someone's garage, but it works perfectly, and for €9.50 you can't really go wrong.

The BDM has a 10-pin connector, but not all pins are actually used, so what you really need is a 2x4 connector. I found this old PC motherboard and desoldered a couple of jumper bridges out of it.

The ECU circuit has a clearly visible location for a BDM connector. Pins 1 (marked by the arrow) and 2 are not used, so you don't need to solder anything there.

Take care while soldering, don't apply too much heat as not to damage the leads or the coating. Once finished, check the connections with a tester if you have one.

Connect the BDM to the parallel port of your computer. Attach the ribbon cable to the ECU, making sure the polarity is correct. The ECU needs to be powered up, see this guide for DC power harness information.
In progress

Finding a PC with a proper LPT port could be challenging these days. In my household the only option was this headless Linux server. I had to use this guide to create a bootable USB stick with DOS and BD32 to flash the ECU while watching the progress on a projector screen, no less ;]

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