I have a PCB with a MCU (ESP32) datasheet that appears to be unresponsive and I am trying to verify whether it is my assembly, circuit, or components which are bad. I connect my board to my PC using a micro-USB which then is connected to the MC using a silicon labs UART bridge chip CP2102N-A02-GQFN28R. As soon as I connect the board, I see the port is recognized which is a good sign. I then attempt a firmware upload but my PC is unable to connect to the ESP32 and eventually times out.
Fortunately, I have used the power circuit and firmware upload circuit on other boards which do work so I would be surprised if the issue was here. However I am doing a few things different with GPIOs and ESPs can be weird about boot failures and strapping pins, which I know too little about.
I have verified: power to ESP32 is adequate, IO0 pulls to GND during firmware upload attempts, EN is normally 3.3V and pulls to GND during boot attempts, checked orientation and for shorts on bridge IC.
Is there a way to rule out a DOA (dead on arrival) ESP32 with my setup? I think I can rule out a DOA bridge IC because the port is recognized.
Edit below I have labeled the voltage readings from a multimeter as soon as I plugged in my board. I notice that USB DP is at 3V and DN is at 0V, however the RXD and TXD out of the bridge IC are both at 3.3V. This seems like a problem here. I checked to see if the two pads were shorted together and they are not.
Best Answer
The ESP32 IC was DOA. I removed the original IC from the board and replaced it with an identical IC. After this firmware updates and other tests were successful.