Atmel SAM R21 Xplained Pro, Руководство пользователя

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Atmel SAM R21 Xplained Pro [USER GUIDE]
42243A-MCU-02/2014
13
Technology, 2450BM15A0015
2
) to create a single 50 ohm unbalanced output/input. This kit has a passive
analog RF switch (Skyworks Solutions Inc, AS222-92LF
3
) connected to the unbalanced output of the
balun. The switch is driven by the RFCTRL1 and RFCTRL2 pins of the ATSAMR21G18A which feature
Antenna Diversity to enable the device to automatically select the best signal from two antennas (can also be
selected manually). The output of the switch is connected to a ceramic chip antenna (Johanson Technology,
2540AT18D0100
4
) and a SMA connector for external antennas.
Table 4-10. RF Connections
Pin on SAM R21
RFP RF balanced output (positive)
RFN RF balanced output (negative)
PA09 / RFCTRL1 RF switch control signal (negative)
PA12 / RFCTRL2 RF switch control signal (positive)
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, “1.8V Operation Modifications” on page 14 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” on page 8 .
To program and debug the ATSAMR21G18A a 2x5 50 mil header has to be mounted above EXT1 as shown in
Figure 1-1, “SAM R21 Xplained Pro Evaluation Kit Overview” on page 4 .
2
http://www.johansontechnology.com/datasheets/balun-filter/2450BM15A0015.pdf
3
http://www.skyworksinc.com/uploads/documents/200252C.pdf
4
http://www.johansontechnology.com/images/stories/ip/rf-antennas/Antenna_2450AT18D0100_v3.pdf