4.3 1.8V Operation
The SAM R21 Xplained Pro board is operated at 3.3V by default, but it also has the possibility of running at lower voltages from an external supply. The EDBG is designed to run from a 3.3V supply and won't work on other voltages, therefore all connections from the EDBG and the on board 3.3V regulator to the ATSAMR21G18A have to be removed. Figure 4-1 shows all components that have to be removed for 1.8V operation.
When the components are removed the kit can be supplied with a desired voltage through the pins marked 3V3 (pin four) and GND (pin two) on the power header described in Xplained Pro Power Header.
To program and debug the ATSAMR21G18A a 2x5 50mil header has to be mounted above EXT1 as shown in Figure 1-1.
Operating the SAM R21 Xplained Pro on other voltages than 3.3V requires physical modifications on the kit using a soldering iron and an external debugger for programming the ATSAMR21G18A.
The on board LED is selected for 3.3V operation, the light level at 1.8V operation is very low. To increase the emitted light level the value of the series resistor can be lowered.
The EDBG functionality can be restored by re-soldering the removed components, they are all 0Ω resistors.
The voltage supplied through the power header is applied directly to the ATSAMR21G18A and the extension headers. Applying a voltage greater than 3.3V may damage the board permanently.
