Feather M4 Express no PWM out on RX (0) or TX (1)

[caternuson]

Re this thread:
https://forums.adafruit.com/viewtopic.php?t=203518

Pinout page indicates PWM out is available on RX and TX:
https://learn.adafruit.com/adafruit-feather-m4-express-atsamd51/pinouts

Test sketch:

#define PWM_PIN 0

void setup() {
  pinMode(PWM_PIN, OUTPUT);
  analogWrite(PWM_PIN, 128);
}

void loop() {
}

Setting PWM_PIN to either 0 or 1 produces no output on either RX or TX (resp).

[philggg]

The documentation for the board is incorrect. if you run this code on the board:

# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries
#
# SPDX-License-Identifier: MIT

"""CircuitPython Essentials PWM pin identifying script"""
import board
import pwmio

for pin_name in dir(board):
    pin = getattr(board, pin_name)
    try:
        p = pwmio.PWMOut(pin)
        p.deinit()
        print("PWM on:", pin_name)  # Prints the valid, PWM-capable pins!
    except ValueError:  # This is the error returned when the pin is invalid.
        print("No PWM on:", pin_name)  # Prints the invalid pins.
    except RuntimeError:  # Timer conflict error.
        print("Timers in use:", pin_name)  # Prints the timer conflict pins.
    except TypeError:  # Error returned when checking a non-pin object in dir(board).
        pass  # Passes over non-pin objects in dir(board).

You will get this list of pwm supported pins:

PWM pins available are:
*PWM on: A1
*PWM on: A3
*PWM on: D0
*PWM on: D1
*PWM on: D10
*PWM on: D11
*PWM on: D12
*PWM on: D13
*PWM on: D15
*PWM on: D17
*PWM on: D25
*PWM on: D4
*PWM on: D5
*PWM on: D6
*PWM on: D9
*PWM on: LED
*PWM on: RX
*PWM on: SCK
*PWM on: SCL
*PWM on: SDA
*PWM on: TX

The board documentation should be fixed.