Unable to program ESP32-C3 from USB

[Sayantan]

Hello,

I am made a project with ESP32-C3-MINI-1-H4 module in the past and it works great. I could program it directly from USB out of the box. But for a newer project I used ESP32-C3-MINI-1-N4 variant. As per the datasheet,

The ESP32-C3FN4 chip and the ESP32-C3FH4 chip vary only in the ambient temperature

. However after making the PCB I can't program it directly from USB.
So I pull the GPIO 9 LOW to put it into boot mode and when I compare it with the previous board that I have I found, in the serial monitor my previous board (based on ESP32-C3FH4 chip) shows

Code: Select all

ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0x15 (USB_UART_CHIP_RESET),boot:0x0 (USB_BOOT)
Saved PC:0x400462e2
wait usb download

while this new board (based on ESP32-C3FN4 chip) shows

Code: Select all

ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0x15 (USB_UART_CHIP_RESET),boot:0x2 (UART0_BOOT)
Saved PC:0x400462e2
wait uart0 download

I don't understand why it functions differently on both modules while rest of the circuit is identical on both boards.
How can I change this boot mode to make the ESP32-C3-MINI-1-N4 module program over USB since I didn't break out the UART pins.
Please help!
Thanks

[ESP_Sprite]

Can you check GPIO8? It should have a high level (either externally or due to the internal pullup)

[Sayantan]

Yes, GPIO 8 has external 10k pullup resistor on both boards

[ESP_Sprite]

Can you check if it's actually doing its job of pulling the GPIO up? There've been some instances with people with issues like you have that had a short to ground under the module.

[Sayantan]

Okay, there are external circuitry connected on the GPIO 8 and I think that might pulling the pin low, I removed it and now I am able to program it via USB, thank you so much for your help.

[ESP_Sprite]

You are welcome!