The groundwork for getting started on this project was laid out in this 2018 EEVBlog forum post. In it, Luiz Renault suggests the data rate is 512kbit/s based on the smallest pulse width. My results before vary slightly but should be in the same range.

The minimal bit length looks to be ~1.740us, not far off Luiz’s 1.960us that can be seen in the scope shot in the second post. So 512kbit/s seems like a reasonable rounding point. Luiz also indicated they were able to decode the data, but not what the content looked like. There was also no indication of byte size, start/stop bits. So more digging….

I found myself in a conversation about ESP32 boot times. Specifically the time it takes from boot until user code can do something useful with an IO.

As this was something relevant to Richmote but I didn’t have any actual data I decided to do a simple setup to measure the results. My test setup consisted of two probes one connected to the RST line and the other to a random GPIO. The firmware would immediately setup the GPIO as an output and pull it HIGH. Nothing else.