Is this repo right for using serial link on ESP32 or ESP8266?

[sglux]

While there are telemetrix servers using Wifi or BLE for both ESP32, I wonder how to use telemetrix on ESP32 boards with a serial link?

The boards we are using all have a hard wired USB port so it would be straight forward and transparently switch between Atmega-based and ESP-based boards.

[MrYsLab]

Thanks for your question. Could you please tell me the board's manufacturer, model number, and the ESP32 device version it uses? The Telemetrix ESP 32 client , and server were designed initially to work with the ESP-WROOM-32 ESP32 ESP-32S Development Boards using either a WIFI or BLE transport. It verifies using a specific set of pins and their operational modes.
Since the library was written, many ESP32 boards and chips have come to the marketplace.
Regarding supporting a serial interface, I need to look at the board you are using before making a decision.

[sglux]

We are using lots of M5STACK modules, such as:

• ESP32-D0WDQ6-V3 https://shop.m5stack.com/products/m5stack-core2-esp32-iot-development-kit-v1-1
• ESP32-D0WDQ6-V3 https://shop.m5stack.com/products/esp32-basic-core-lot-development-kit-v2-7
• ESP32-S3 https://shop.m5stack.com/products/m5stack-cores3-lite-esp32s3-iot-dev-kit
  amongst others.

There are also some self-designed boards that use an ESP32-WROOM-32UE-N8 with a CP2101 UART-USB interface similar to nodeMCU boards.

[MrYsLab]

Thanks for providing that information. The m5stack boards contain some very interesting integrated peripherals. I am not likely to support any of them in Telemetrix. If you would like to program the boards in Python, have you considered using MicroPython with an editor such as Thonny?
You can do simple things, such as input pin control:

from machine import Pin
import time

# Define the pin number you want to use as input.
# Replace 'YOUR_PIN_NUMBER' with the actual GPIO number of the pin you're using.
# For example, if you're using M5Stack Basic's physical button A, it's typically Pin(39).
input_pin_number = 39 

# Create a Pin object, configuring it as an input with a pull-up resistor.
# PULL_UP is often used for buttons to ensure a defined state when not pressed.
input_pin = Pin(input_pin_number, Pin.IN, Pin.PULL_UP)

print(f"Monitoring input on Pin {input_pin_number}...")

while True:
    # Read the digital value of the pin.
    # For a button with a pull-up, 0 typically means pressed, and 1 means released.
    pin_value = input_pin.value()

    if pin_value == 0:
        print("Button Pressed!")
    else:
        print("Button Released.")

    time.sleep(0.1) # Small delay to prevent excessive printing and debounce

You may also control the peripherals using micropython.

[sglux]

Well, Micro Python indeed is an interesting option in general.

Right now, there is no need to control the peripherals on the M5Stack! Controlling I2C, SPI and GPIO/ADC is all that is needed.

But for the current task, a generic firmware on the ESP, that can be controlled from the PC is perfect, as our calibration procedures only exist on the PC side, and there is no plan to shift that onto the ESP board.

Basically, the M5 Stack adopts the USB-to-UART pinning from the NodeMCU-Wroom, so TXD is on GPIO01 and RXD on GPIO03.

[MrYsLab]

Adding a serial interface is not trivial, so before I commit to doing this, I want to ensure that the pinout I support meets your needs.
If you look at this link for the pins that the library supports, does this meet your needs? Currently, this is a fixed set and one I do not wish to change.

If I do commit to adding a serial interface, I do not know how much time it will take to implement the code. The changes that need to be made are to both the asyncio and threaded servers. Also, a new serial server will need to be implented. The time frame would be from several weeks to perhaps a few months.

Do you wish for me to proceed with serial interface?

[sglux]

If you look at this link for the pins that the library supports, does this meet your needs? Currently, this is a fixed set and one I do not wish to change.

Well, all relevant pins do exist, so everything fine for me.

The only point to discuss might be what happens to the two pins occupied by the uart telemetrix is "running on". For the Arduino it is solved, maybe could be the same on ESP/ESP32.

I tried to compile a list of which pins are most often used for the UART on the USB-port of the boards:

MCU Family	TX	RX	Logic Level	Bootloader / Flash UART
ATmega328P	PD1 (D1)	PD0 (D0)	5 V	UART0
ESP8266	GPIO1	GPIO3	3.3 V	UART0
ESP32	GPIO1	GPIO3	3.3 V	UART0
ESP32-C3	GPIO21	GPIO20	3.3 V	UART0
RP2040	GPIO0	GPIO1	3.3 V	USB (native)
STM32F103	PA9	PA10	3.3 V	USART1

So, GPIO1 and GPIO3 is also used in all my boards...

[MrYsLab]

The Telemetrix servers do not offer an option to select the UART pins. The pins in use for each board are dictated by the Arduino Core libraries for each board. Support for the Raspberry Pi Pico (non-WIFI) does not use an Arduino Core, but the Raspberry Pi SDK for the Pico. The Pico W does use an Arduino Core, but does not support a serial interface. Only the non-Wi-Fi version does.

You should test each board to ensure that serial communication is functional. For the ATmega, ESP, and STM32 boards, you can easily do so using a simple Arduino Sketch installed using the Arduino IDE, such as:

int counter = 0;

// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(115200);
}

// the loop routine runs over and over again forever:
void loop() {
  
  Serial.println(counter++);
  delay(1);  // delay in between reads for stability
}

For the RP2040, you can try running the included loopback example.

I started working on providing a serial interface to the Pico W version, but it is unclear when I may complete it.

[sglux]

Ok, let's simplify it a bit: what needs to be done, to get the telemetrix server running on the default serial interface that the arduino libraries already use on the ESP-based boards.
I did not expect it to be too complicated, as the serial interface on the Atmega-based arduino already exists.
Mustn’t the stream be redirected to UART instead of WiFi/BLE?

[MrYsLab]

Yes, that is what needs to be done on the server side, but since the ESP32 Telemetrix libraries support unique ESP32 features such as touch pins and digital-analog converters, the clients also need to be modified for a serial interface.

I am unwilling to do the work on the server side without providing updated clients as well, and that will take time to do.

If you are only interested in the server-side implementation, you may be willing to implement it yourself. If you compare Telemetrix4UnoR4WIFI and Telemetrix4UnoR4SerialUSB as examples, it should provide enough guidance to do so.

I would be willing to provide any guidance you need to implement the server on your own.