Can't upload to ESP32-C3 -- UART too fast?

[trschneider1]

Trying again, it seems my previous attempt to post didn't make it...

I am trying to program a custom ESP32-C3 board, and the UART seems to be running at 2.5x speed. Instead of 115.2kbaud, its something closer to 288kbaud, which isn't even a valid baud rate. Looking at it on the oscilloscope, it appears to be a valid transmission packet, just at the wrong speed. I've already verified that I'm using a 40MHz crystal as recommended. We have a previous revision of this board which used the ESP32-C3-MINI-1 module, and that one runs fine. We just rolled that circuitry right onto the PCB, so I wouldn't expect any issues. Has anyone seen something like this before? Any suggestions?

[ESP_Sprite]

Strange. Possibly an issue with the load capacitances of the crystal, making it oscillate at a harmonic?

[andreko]

Hi just my two cents on this. At least for the ES32-C2 I found out that the default hardware setting for the main XTAL frequency in sdkconfig was wrong for the dev board I was using. It was set to 40MHz instead of 26MHz, which is the correct setting.
Maybe this is the same for the ESP-C3 setup.

[trschneider1]

Found the problem - I had the wrong footprint for the crystal. Its a 4-pin package and I had the wrong two pins connected to the ESP32, while the actual crystal pins were being grounded on the PCB. Not sure how the ESP32 was seeing any oscillation at all, but I don't care enough to dig into it further
Anyway, I rotated the xtal on the board, and all is good now.