That is strange for sure... any chance you can capture what the chip sends on U0TXD when this happens? Problem solved! Turns out it was a purely software issue - basically I have some code that monitors the serial port and parses the incoming data, but I wasn't adding in checks for unexpected data....

Could it be that there's too much parasitic capacitance on GPIO0 to make the built-in pullup pull the line up in time? How long are your lines, what else is connected to GPIO0? Hmm - the trace length is 24mm. You can see a screenshot of the relevant layout below. However, I've tried directly shorti...

Hello all, I've designed a custom 2-layer PCB using an ESP32-D0WD V3. I'm using a MircroMatch connector as a programming interface, routing the EN, BOOT and UART pins there. I'm having an issue whereby the boards will fail to start up normally, unless the U0RXD pin is pulled up or down via a resisto...