Hi, about the problem not being able to upload a sketch when the commu is attached to the core2; I found the culprit: it's gpio2-pin (core2) to the M5-bus pin 15, which is the INT-output of the MCP2515-chip. Pin 2 of the ESP is a strapping pin which needs to be low when uploading a sketch, while the MCP-chip pulls it to high-level. A dirty fix is to wire-wrap the pin2 to a button that can ground the pin during sketch-upload.
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RE: Core 2 and COMMU