ESP32-C3-WROOM-02 Boot

[yellowriver81]

Hello,

I recently designed a PCB using the ESP32-C3-WROOM-02 microcontroller. I am using the built-in USB-JTAG interface. I put a pull-down pushbutton on `GPIO9` for `BOOT`. However, I realized that I forgot to connect `GPIO8` to `3V3` (it was originally connected to another chip that I later removed, but I forgot to tie the pin high). I attached the relevant part of the schematic below.

ESP32-C3-WROOM-02 Schematic Part.png (39.1 KiB) Viewed 252 times

According to the technical reference manual, in order to enter the joint download mode, `GPIO9:GPIO8` needs to be `0:1` on reset. Because the PCBs were already fabricated, I am trying to find a way to reliably upload and debug programs without having to invasively modify the board (e.g., by soldering a rework resistor on `IO8`). My idea was that the first time I flash the board, I will manually hold a jumper from `IO8` to `3V3` at the same time as pulling BOOT low.

My question is, do I need to do this for later flashes? I read from https://docs.espressif.com/projects/esp ... -using-usb that

If you are flashing for the first time, you need to get the ESP32-C3 into the download mode manually. To do so, press and hold the `BOOT` button and then press the `RESET` button once. After that release the `BOOT` button.

Does this imply that after I have flashed the MCU once, I do not need to ensure that `IO8` is tied high while I upload a program using ESP-IDF (esptool) in subsequent program uploads... or is `IO8 = 1` something that I have to ensure every time a program is uploaded?

Thanks in advance for your help!

[Sprite]

No, if you switch to download mode at runtime, you don't need GPIO8/9 to be in any particular state. Note that if something goes wrong with flashing or e.g. your firmware accidentally reconfigures the USB pins, you may to hotwire GPIO8 again to get the board back into download mode, but that shouldn't happen too often during normal use.