User Manual

Atmel SAM R21 Xplained Pro [USER GUIDE]
42243B-MCU-06/2014
11
Pin on EXT3 SAM R21 pin Function Shared functionality
10 [SPI_SS_B/GPIO] PA08 GPIO EDBG
11 [TWI_SDA] PA16 SERCOM1 PAD[0] I²C SDA EXT1 and EDBG
12 [TWI_SCL] PA17 SERCOM1 PAD[1] I²C SCL EXT1 and EDBG
13 [USART_RX] - -
14 [USART_TX] - -
15 [SPI_SS_A] PA14 GPIO EDBG
16 [SPI_MOSI] PB22 SERCOM5 PAD[2] SPI MOSI EXT1 and EDBG
17 [SPI_MISO] PB02 SERCOM5 PAD[0] SPI MISO EXT1 and EDBG
18 [SPI_SCK] PB23 SERCOM5 PAD[3] SPI SCK EXT1 and EDBG
19 [GND] - GND
20 [VCC] - VCC
4.1.2 Other Headers and Connectors
There are two headers that are not mounted on the kit from production. These headers contains signals that
are otherwise not easily accecible on the kit.
4.1.2.1 Altnernate Signals Header
The alternate signals header is marked with "Alternate" in silkscreen of the kit, the signals provided here are
otherwise hard to do measurements on.
Table 4-3. Alternate Signals Header
Pin on header Pin on SAM R21 Function
1 PA09 RFCTRL1, negative antenna switch control signal
2 PA12 RFCTRL2, positive antenna switch control signal
3 PA27 GPIO, chip select on the EDBG DGI SPI bus
4.1.2.2 Cortex Debug Connector
The Cortex debug connector is provided to enable external debuggers to be connected to the
ATSAMR21G18A. The footpring is made for a 2x5 50mil connector and the pinout is shown in Table 4-4,
“Cortex Debug Connector” on page 11. This header should only be used when the EDBG is disconnected
from the target, for more information see “1.8V Operation” on page 13.
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 crystals 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