Code size report:

Reference:  rp2/CMakeLists.txt: Require boards to define PICO_FLASH_SIZE_BYTES. [44a569b]
Comparison: samd/boards: Fix pin mappings for Seeed XIAO SAMD21 Plus. [merge of a4e76e9]
  mpy-cross:    +0 +0.000% 
   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
      esp32:    +0 +0.000% ESP32_GENERIC
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO_W
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:    +0 +0.000% VIRT_RV32

What is the difference to the already-supported Seed XIAO SAMD21? I do not find a XIAO SAMD21 Plus board at the Seeed homepage, and the URL in your files points to the already supported device.

It seems that the only substantial change is extending the pins.csv file. That change does not need a new board definition. Instead you can make a PR for the actual board files with the suggested changes. About the actual list I have a few minor comments:

• There is no button at the XIAO SAMD21 board, and PB22 is not connected.
• It seems a common habit for Arduino to have a LED found at D13. But different to other Arduino D11 to D13 are not accessible for users, an the LEDs have their own entries in the Pin list.
• There are two entries for the User LED, LED and USER_LED. One of the should go.
• There is no TX_LED item.
• The SAMD21 port#s memory is very limited, and every line in the pins.csv uses flash space. So better keep the table as short as possible. That was the reason to call the pins Ax_Dx, besides that Seeed calls them so in the schematics.

But maybe you have better information and there will be a new version of the XIAO SAMD21 board, like with a button. Then, one could introduce variants.

Like @robert-hh I am confused that I can't find any other information about this board.

@cumin777 I see you seem to work for Seeed, is this a new product that is not yet announced?

The board profile in this PR looks OK. I see you have added a board image here: micropython/micropython-media#120 - thanks!

Probably my only real suggestion is that we wait until this board is announced before we merge the new profile.

Sorry, I forgot to explain this

This is a new board that we will release and publish. Compared with the existing XIAO SAMD21, the main difference is that more MCU resources are exposed on the new board.

The URL currently in the files is only a temporary placeholder because the official product page has not been published yet. I will provide the correct URL as soon as the product is officially released.

For the pin list comments, thank you. I will revise the pins.csv accordingly and keep it as compact as possible.

@cumin777 No problems. Please leave another comment once the new board is announced and the product page is online.