RE: USBD Serial Basics

Alex Anderson — Thu, 05 Nov 2026 17:24:23 GMT

Oh, so to explain, there's a peripheral heart rate sensor which has a usb-c connector. That's not the device I intend to control. What I found in the source code is that sensor seemingly works with a few gpio pins, obviously first impressions would make you think, usb-c cable, usb related things are going on. Which is not in fact the case. Unfortunately for me, the usb stack has been completely removed.

I need serial communication, I think I'm close to getting the usb stack re-enabled and serial working, but clearly I'm missing something. The interrupt handler that's present should echo messages back (so that I can verify that it works). I'm getting nothing. I'm also somewhat working in the dark because usually with microcontrollers I have some printf debugging, but obviously since that's what's missing here. I don't know what progress if any I'm making exactly. I'm somewhat hoping someone can walk me through what I should be doing to get this to work.

Here are the changes I've made:
bitbucket.org/.../65f600450417e258a898f6d414ac02117cd49fbf

RE: USBD Serial Basics

Benjamin — Thu, 05 Nov 2026 13:52:48 GMT

Hi Alex,
Thanks for reaching out. Before we help you can you clarify this. When you say the sensor is controlled “like an i2c device,” do you mean the port is just a connector carrying I2C signals? If so, no USB protocol is involved, and enabling the USB stack won’t help with the sensor.

Best regards,
Benjamin