<![CDATA[ESP32 and RS485]]>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?

]]>https://community.m5stack.com/topic/8123/esp32-and-rs485RSS for NodeTue, 28 Apr 2026 23:39:55 GMTSat, 07 Mar 2026 23:28:27 GMT60<![CDATA[Reply to ESP32 and RS485 on Sun, 08 Mar 2026 21:22:58 GMT]]>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

]]>https://community.m5stack.com/post/30741https://community.m5stack.com/post/30741Sun, 08 Mar 2026 21:22:58 GMT