ESP32 Forum

Hello,
I'm currently working with an ESP32-CAM board, so I don't have many pins available for external communication (I'm using both the camera and the PSRAM). I need to communicate the board via RS485, so I need 3 pins to make it work. I'm currently using GPIO12 (the only "free" pin I have left) for the RX ENABLE signal, but I still need TX and RX so I thought "well, I can use GPIO1 and GPIO3 for this", but the thing is that after setting the pins for UART_NUM_2, I loose serial output to the terminal even if I don't output anything via UART_NUM_2. Reading through the Technical Reference Manual I can't find anything that suggests that I can't use two peripherals on the same pins, but maybe this is related to UART_NUM_0 being routed via IOMUX and UART_NUM_2 via the GPIO Matrix. It would be nice to have this two UARTs because the RS485 line that I'm connecting to works at 9600 bauds and the ESP32-CAM works at 115200.

My question is: Is it possible to attach two UART peripherals to the same pins? And if so, how can I work around my current situation? I know that I can simply lower the baudrate for the ESP32 serial port but I would much rather have two separate peripherals.

You cannot connect two output signals to the same pin. (Conceptually: if you could, and one signal would drive the pin high and the other drives the pin low, you would have a short.)

Thanks! Reading your reply it seemed obvious; the UART that is not "talking" wants to drive TX high (idle), so nothing can go through. Not sure why it didn't occur to me.

PD: This was my first time using the forum and I'm amazed at how fast you replied! Thanks again

Hi ESP_Sprite,
If you are constrained by I/O pins, use a multiplexer to solve this problem. If you need more help, send a detailed use case.
Best,
Akshay

You may be able to get away without a DE/RE signal, saving one I/O pin: https://docs.espressif.com/projects/esp ... r-receiver