4.1.3.

Current Measurement Header

An angled 1x2, 100mil pin-header marked with MCU current measurement is located at the upper edge of

the SAM R21 Xplained Pro. All power to the ATSAMR21G18A is routed through this header. To measure

the power consumption of the device remove the jumper and replace it with an ammeter.

Caution:  Removing the jumper from the pin-header while the kit is powered may cause the

ATSAMR21G18A to be powered through its I/O pins. This may cause permanent damage to the

device.

4.1.4.

Cortex Debug Connector

The Cortex

ATSAMR21G18A. The footprint is made for a 2x5 50mil connector and the pinout is shown in the table

below. This header should only be used when the EDBG is disconnected from the target. For more

information, see 1.8V Operation.

Table 4-4. Cortex Debug Connector

Pin on connector

Connected

Function

1

VCC Target

Voltage reference

2

PA31_SWDIO

Debug data

3

GND

GND

4

PA30_SWCLK

Debug clock

5

GND

GND

6

NC

-

7

NC

-

8

NC

-

9

GND

GND detect

10

RESETN

Target reset

4.2.

Peripherals

4.2.1.

Crystal

The SAM R21 Xplained Pro kit contains one crystal that can be used as clock source for the SAM R21

device. The crystal has a cut-strap next to it that can be used to measure the oscillator safety factor. This

is done by cutting the strap and adding a resistor across the strap. More information about oscillator

allowance and safety factor can be found in application note AVR4100.

Note: 

The 16MHz crystal is connected directly to the RF die inside the SAM R21. The clock signal generated by

the crystal is routed from the CLKM pin on the RF die to a GCLK I/O pin on the microcontroller. For more

information on how the RF die is connected to the microcontroller and how to configure the CLKM pin,

see the SAM R21 datasheet.

Atmel SAM R21 Xplained Pro [USER GUIDE]

Atmel-42243D-SAM-R21-Xplained-Pro_User Guide-04/2016

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