Using UART0 pins as GPIO on ESP32-C3

[designrulesco]

I'm having an issue using the UART0 pins (20,21) on the ESP32-C3 (specifically ESP32-C3-WROOM-02 module) as GPIOs (specifically, inputs).

I'm using the latest generic 1.25.0 image and set the pins to inputs, but it doesn't work. I use some regular GPIO's in the same manner and they properly trigger and poll with value changes. Espressif says these can be used as GPIO's, but I'm wondering if there's anything strange/specific to micropython preventing me from doing so and if anyone had any guidance.

I don't need the hardware UART (not using it), and am just using USB Serial.

Code below.

import time

pins = {
    'bit1 (GPIO7)':  Pin(20,  Pin.IN),
    'bit2 (GPIO10)': Pin(21, Pin.IN),
    'bit3 (GPIO20)': Pin(7, Pin.IN),
    'bit4 (GPIO21)': Pin(10, Pin.IN),
    'bit5 (GPIO0)':  Pin(0,  Pin.IN),
}

last = {name: p.value() for name, p in pins.items()}

print("Starting poll‑loop. Flip SPDT switch and watch the changes…")

while True:
    for name, p in pins.items():
        v = p.value()
        if v != last[name]:
            print(f"{name} -> {v}")
            last[name] = v
    time.sleep_ms(20)```

[Josverl]

You can use GitHub Flavored Markdown to format your posts. In particular use 'triple backtick'
```py
# code goes here
``` around your code snippets to get syntax highlighting and proper indenting.
Also see the section https://github.com/orgs/micropython/discussions/9111

[designrulesco]

Thanks, fixed.

[Josverl]

is it intentional that the names and the pins are mismatched ? (only Pin 0 lines up with its description)

I tried with a basic test of my own and I can use all these pins as an input om a wemos esp32_c3 mini ,
except pin-0 as that is not broken out.

test was just touching a 3.3v wire

Details

from time import sleep, sleep_ms
from machine import Pin

# Define the pins to monitor
pin_numbers = [0, 7, 10, 20, 21]
print(f"GPIO {pin_numbers} input test")

pins = {pin: Pin(pin, mode=Pin.IN, pull=Pin.PULL_DOWN) for pin in pin_numbers}

# Store previous values
print([f"p{pin}= {pins[pin].value()}" for pin in pin_numbers])
prev_values = {pin: pins[pin].value() for pin in pins}

while True:
    # Get current values
    cur_values = {pin: pins[pin].value() for pin in pins}
    # Check if any value changed
    if cur_values != prev_values:
        # Update previous values
        prev_values = cur_values.copy()
        # Print the changed values
        print([f"p{pin}= {cur_values[pin]}" for pin in cur_values])
    sleep_ms(100)

import main
GPIO [0, 7, 10, 20, 21] input test
['p0= 0', 'p7= 0', 'p10= 0', 'p20= 0', 'p21= 0']
['p0= 0', 'p7= 1', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 0', 'p10= 1']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 1', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 1', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 1', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 1', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 1', 'p20= 0', 'p21= 0', 'p10= 0']
['p0= 0', 'p7= 0', 'p20= 0', 'p21= 0', 'p10= 0']

[designrulesco]

Hi Josverl - thanks for checking. The mismatches naming in the print statements is just a mistake, but the pins themselves are correct.

What image are you using? I installed v1.25 for ESP32 C3 via Thonny and this didn't work. Is there a different image for the wemos that maybe doesn't bind the REPL to UART0 that enables this to work for you but not for me?

[shariltumin]

The "ESP32_GENERIC_C3" firmware enables REPL on UART0 by default. This is defined in "boards/ESP32_GENERIC_C3/mpconfigboard.h"

#define MICROPY_HW_ENABLE_UART_REPL         (1)

You can try to download and flash the "LOLIN_C3_MINI" firmware to your board, as this does not attach UART0 to REPL.

[designrulesco]

Is there something that LOLIN_C3_MINI changes that would be inappropriate or affect functionality when used on an ESP32-C3-WROOM-02? Or is it functionally identical in most ways while also untying the REPL on UART0?

Alternatively, do you think I could modify mpconfigboard.h and rebuild ESP32_GENERIC_C3 to disable REPL on UART0?

[Josverl]

making the change is simple with any editor.
And building the firmware is simple using mpbuild on any *nix or Windows/WSL2 system that can run containers (docker or similar)