Table 4-5. External 32.768kHz Crystal

Pin on SAM R21

Function

PA00

XIN32

PA01

XOUT32

Table 4-6. External 16MHz Crystal

Pin on SAM R21

Function

XTAL1

XIN

XTAL2

XOUT

4.2.2.

Mechanical Buttons

SAM R21 Xplained Pro contains two mechanical buttons. One button is the RESET button connected to

the SAM R21 reset line and the other is a generic user configurable button. When a button is pressed it

will drive the I/O line to GND.

Table 4-7. Mechanical Buttons

Pin on SAM R21

Silkscreen text

RESETN

RESET

PA28

SW0

4.2.3.

LED

There is one yellow LED available on the SAM R21 Xplained Pro board that can be turned on and off.

The LED can be activated by driving the connected I/O line to GND.

Table 4-8. LED Connections

Pin on SAM R21

LED

PA19

Yellow LED0

4.2.4.

USB

The SAM R21 Xplained Pro has a Micro-USB receptable for use with the SAM R21 USB module. To be

able to detect when a USB cable is connected, a GPIO/ADC is used to detect the VBUS voltage on the

connector.

Table 4-9. USB Connections

Pin on SAM R21

USB

PA07

VBUS Detection

PA24

USB D-

PA25

USB D+

4.2.5.

RF

The main feature of SAM R21 Xplained Pro is to show the RF capability of the ATSAMR21G18A device.

This device has bidirectional 100Ω differential antenna pins, which are fed through a balun (Johanson

Technology, 2450BM15A0015) to create a single 50Ω unbalanced output/input. This kit has a passive

analog RF switch (Skyworks Solutions Inc, AS222-92LF) connected to the unbalanced output of the

Atmel SAM R21 Xplained Pro [USER GUIDE]

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

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