[espressif / lolin_s2_mini] Inconsistency in defined pins

[bato3]

There is some inconsistency in the Lolin S2 Mini plate.

The chip itself may have freely configured pins as i2c, sleep, uart, and the tile itself has no descriptions, only numbers.

Some of the pins were defined as compatible with the Lolin D1 Mini.

Similarly with S3 Mini, where there are only numbers directly on the tile, but in Pinout there are descriptions: https://www.wemos.cc/en/latest/s3/s3_mini.html

SCL, SDA, SCK, Miso, Mosi, but not RX and TX (SS - I suggest skipping) were defined.

The method of Board.spi (), but there is no Board.I2c () (not to mention UART ...)

I am asking for unification: adding missing pins / methods.

[dhalbert]

Are you interested in doing a pull request yourself? That would be great. Most of us don't have a board to test.

[bato3]

Is there any procedure for them to accept the code? (Some confirmation of license acceptance or something similar?)

And direct me to what tests should be performed, because the instructions are probably this: https://learn.adafruit.com/building-circuitpython/espressif-build

[tannewt]

No license acceptance. The license that applies is in the file headers.

Test the build on your board to make sure it works. After you PR is proposed, further tests will be run automatically.

More details here: https://learn.adafruit.com/contribute-to-circuitpython-with-git-and-github

[romkey]

I don't think you should add labels for RX and TX; the board doesn't expose those pins on its headers.

I've used the Lolin S2 mini in a few designs. It's a nice board and its footprint compatibility with the D1 mini is helpful. I was very frustrated by the lack of access to RX and TX when I had crashes and couldn't get the exception information over USB CDC and had no access to TX.

You can confirm this in ESP32-S2 data sheet; on page 14 in section 2.2 "Pin Description" it specifies that RX and TX (U0RXD and U0TXD) are GPIO44 and GPIO43.

Unfortunately the Lolin S2 mini doesn't make those pins available, so I think it would be misleading to define them.

[deshipu]

I don't think you should add labels for RX and TX; the board doesn't expose those pins on its headers.

I've used the Lolin S2 mini in a few designs. It's a nice board and its footprint compatibility with the D1 mini is helpful. I was very frustrated by the lack of access to RX and TX when I had crashes and couldn't get the exception information over USB CDC and had no access to TX.

I think there is some confusion here. The ESP32-S2 and ESP32-S3 chips have real USB support, and the USB serial for the REPL is a simulated serial device – it has no pins, it just writes to USB directly, not like on the ESP32 chips that don't have USB support, and have to rely on a separate serial-to-usb chip, connected to real gpio pins on the board.

That doesn't mean that there can't be pins named board.RX and board.TX that are used by default when creating board.UART() – it's a completely separate thing from the USB serial.

[romkey]

I understand that.

On an ESP32 series chip, I think that board.RX and board.TX should reflect UART0's RX and TX pins, and on the Lolin S2 mini those pins aren't exposed on the headers, which is why I don't think they should be added to the pin definitions (and why they aren't there currently).

[deshipu]

They are just the default UART. It doesn't matter which one. It's just a convenience.

[anecdata]

There's nothing on the silk or in the docs indicating default RX and TX pins. Some D1-form-factor boards have default (silk + docs) RX and TX in the upper right (USB-connector side, connector at the bottom), but not all.

[dhalbert]

To be clear here, it sounds like GPIO43 and GPIO44 are not exposed at all on the Lolin S3 S2 Mini, and would not be available except via bodge wiring to the chip pins. In that case, there should not be board.RX and board.TX pins

@deshipu I don't understand if the pins are not accessible why they would be listed. Maybe you meant something else?

[romkey]

Why would you define board.RX and board.TX when you can't actually wire anything up to the module's default UART pins on that board? Why would you define the "default UART" pins to be something other than what the data sheet specifies? What pins would you propose that board.RX and board.TX be in that case? (edit: cross posted with Dan's comment)

[romkey]

@dhalbert they're not exposed on the S2 mini - they are exposed on the S3 mini. But I think this issue was about the S2 mini.