ESP32 and RS485

alex9

Hi,

I'm trying to use the RS485 interface on the M5Stack StampPLC (ESP32-S3 based) to transmit a test signal

Problem:

GPIO 0 measures 0V with a multimeter (should be 3.3V idle for UART)
No signal appears on the oscilloscope — only millivolt noise
Serial Monitor shows nothing (USB-CDC may not be configured)

Questions:
-Is GPIO 0 the correct TX pin for RS485 on StampPLC, or does it have a different pinout?

-What are the correct build_flags in platformio.ini to enable USB-CDC on the ESP32-S3 variant used in StampPLC?

-Is there an official StampPLC Arduino/PlatformIO example for RS485 communication?

felmue

Hello @alex9

it looks like yes, GPIO0 is TX pin for RS485. See pinmap here.

The platformio.ini example can be found here.

Running a quick search I did not find an RS485 example, sorry.

Edit: Maybe try this RS485 library.

Thanks
Felix