User Manual

RST - this is the Reset pin, tie to ground to

manually reset the ATSAMD51, as well as launch

the bootloader manually

ARef - the analog reference pin. Normally the

reference voltage is the same as the chip logic

voltage (3.3V) but if you need an alternative analog

reference, connect it to this pin and select the

external AREF in your firmware. Can't go higher

than 3.3V!

Debug Interface

If you'd like to do more advanced development, trace-

debugging, or not use the bootloader, we have the

SWD interface exposed.

You can use any 2x5 0.05" pitch SWD interface to

connect. We suggest a J-Link, its supported by every

IDE/software that can program the ATSAMD51.

On the Metro M4 Express AirLift, at least for now, AREF is tied to 3.3V due to a silicon v0 bug that does not

allow the DACs to work unless AREF is connected to 3.3V. You cut the bottom jumper if you need a different

AREF voltage but note that this may change DAC range!

