[Grbl_Esp32 Issue#86] Serial on pins?

#1 – bdring 于 2019-02-04

Those are used for USB UART, but you can create another TTL UART with just about any free pins.

#2 – 109JB 于 2019-02-04

So I should be able to upload and configure the ESP32 using USB and then connect the GPIO pins 1&3 to the other MCU and use them for serial com between the two as long as I am not using the USB at the same time. Is my understanding correct?

#3 – bdring 于 2019-02-04

No.

The ESP32 has 3 serial ports. Leave the current one connected to the USB alone.

Define a new UART on different IO pins and use that for your apication.

Google “ESP32 Arduino Second Serial Port” for help

#4 – 109JB 于 2019-02-04

I think you misunderstand. When using the pins for external comm, the USB wouldn’t even be connected. Only external power to the Vin pin. There wouldn’t even be a USB cable plugged in. I would only use the USB cable for flashing and when doing that would unplug the other MCU from the GPIO 1&3.

#5 – bdring 于 2019-02-04

I understand.

The USB chip is hardwired to those pins. I don’t think it is a robust design if multiple drivers are on those lines even if you don’t intend to ever power them at the same time.

Grbl_ESP32 has system in place to easily deal with additional source of commands and status requests, for serial, bluetooth and Wifi. It would be easy to add another.

The current serial port is a bit of an exception, because it is the basic is the basic debugging port. Grbl will send data out that port regardless if the USB is connected. Things like the startup string and pushed messages could interfere with your protocol.

Note: At the current time, we have no plans to add a display to the main development branches. The current thought is the best touch interface is a smart phone or tablet. We support that via Bluetooth and Wifi.

#6 – 109JB 于 2019-02-04

OK. Thanks for the explanation. I’ll look into adding an additional port.

#7 – Protoneer 于 2021-05-20

@bdring would it be possible to have two pins (13,14) being able to do UART or I2C? (Based on machine file)

#8 – bdring 于 2021-05-20

It requires extra programming to define what those pins do.

The OLED is an example. See the Custom folder.

#9 – Protoneer 于 2021-05-20

@bdring Thanks!!!