Problems with BMW I-/K-Bus with MCP2025 or TH3122.4

Using Arduino Project Guidance
1

Hello everyone,

I'm Tim and new here. I could really use some help. I've been trying for quite a while to simulate a CD changer using the IbusTrx library. Initially, it worked somewhat with the MCP2025 and the Mega. For days now, though, I've had the issue that my MCP2025 no longer sends anything on the bus, or only very sporadically.

It can still read data — I've tested that. The Mega also sends the message — I've tested that as well. But the messages just don't appear on the bus itself anymore.

At first, I thought the chip might be damaged, so I replaced it. Same problem. Sometimes, the chip even gets incredibly hot.

Then I got the TH3122.4. Same story here, except now it doesn’t work at all. As soon as I connect the TH3122 with the circuit specified in the datasheet, or a modified version from “Curious Ninja,” the chip heats up significantly and causes the bus to crash.

What am I doing wrong? Has anyone experienced the same problem and can offer some advice?

Thanks a lot!

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Start debugging by printing the message to serial monitor just before it's sent from the controller.

Without code, schematics, datasheet links we don't have a fair chanse to pinpoint the fault.