Adafruit Feather M4 Express Manual page 144

Where's my UART?
On the SAMD21, we have the flexibility of using a wide range of pins for UART. Compare this to some chips like the
ESP8266 with fixed UART pins. The good news is you can use many but not all pins. Given the large number of SAMD
boards we have, its impossible to guarantee anything other than the labeled 'TX' and 'RX'. So, if you want some other
setup, or multiple UARTs, how will you find those pins? Easy! We've written a handy script.
All you need to do is copy this file to your board, rename it code.py, connect to the serial console and check out the
output! The results print out a nice handy list of RX and TX pin pairs that you can use.
These are the results from a Trinket M0, your output may vary and it might be very long.
and SERCOMs check out our detailed guide here
© Adafruit Industries
(https://adafru.it/Ben)
https://learn.adafruit.com/adafruit-feather-m4-express-atsamd51
ItsyBitsy M0 Express and ItsyBitsy M4 Express
Connect USB on the ItsyBitsy to VIN on the GPS
Connect G on the ItsyBitsy to GND on the GPS.
Connect RX/0 on the ItsyBitsy to TX on the GPS.
Connect TX/1 on the ItsyBitsy to RX on the GPS.
Metro M0 Express and Metro M4 Express
Connect 5V on the Metro to VIN on the GPS.
Connect GND on the Metro to GND on the GPS.
Connect RX/D0 on the Metro to TX on the GPS.
Connect TX/D1 on the Metro to RX on the GPS.
For more details about UARTs
Page 149 of 183