ATSAM4S-WPIR-RD Atmel, ATSAM4S-WPIR-RD Datasheet - Page 13

• Manufacturer Part Number: ATSAM4S-WPIR-RD
• Description: Development Boards & Kits - ARM SAM4S16 W.PIR CAMERA REF. DESIGN
• Manufacturer: Atmel

Specifications of ATSAM4S-WPIR-RD

• Rohs: yes
• Product: Reference Designs
• Tool Is For Evaluation Of: ATSAM3S4BA
• Core: ARM Cortex M3
• Interface Type: JTAG, USB
• Operating Supply Voltage: 5 V
• Data Bus Width: 32 bit
• For Use With: RF231USB-RD

4.4
4.4.1
On-board radio transceiver
With the AT86RF231, the board is equipped with a low-power 2.4GHz transceiver designed for industrial and consumer
IEEE
ceramic chip antenna. Interconnected with the MCU, it provides a compact radio interface on a single chip.
The transceiver comprises the analog radio transceiver and the digital modulation and demodulation including time and
frequency synchronization and data buffering. The number of external components is minimized such that only the
antenna, the crystal and decoupling capacitors are required. The bidirectional differential antenna pins are used for
transmission and reception, thus no external antenna switch is needed.
An internal 128byte RAM for RX and TX buffers the data to be transmitted or the received data. Two on chip low
dropout voltage regulators provide the internal analog and digital 1.8V supply.
The transceivers further contain comprehensive hardware-MAC support (Extended Operating Mode) and a security
engine (AES) to improve the overall system power efficiency and timing.
Radio transceiver reference clock (CLKM)
The integrated radio transceiver is clocked by a 16MHz reference crystal. The 2.4GHz modulated signal is derived from
this clock. Operating the node according to IEEE 802.15.4 [3], the reference frequency must not exceed a deviation of
±40ppm. The absolute frequency is mainly determined by the external load capacitance of the crystal, which depends
on the crystal type and is given in its datasheet.
The radio transceiver reference crystal, Q2, shall be isolated from fast switching digital signals and surrounded by a
grounded guard trace to minimize disturbances of the oscillation. Detailed layout considerations can be found in
Chapter 5.
The RF231USB-RD uses a SIWARD SMD/SX-4025 crystal with two load capacitors of 12pF each. To compensate for
fabrication and environment variations, the frequency can be further tuned using the radio transceiver register
XOSC_CTRL (0x12) (refer to [2],
The reference frequency is also available at the CLKM pin of the radio transceiver and depending on the related register
setting. It is divided by an internal prescaler, thus clock frequencies of 16MHz, 8MHz, 4MHz, 2MHz, 1MHz, 250kHz or
62.5kHz are possible. Initially the transceiver master clock is outputted prescaled by 16 (1MHz clock output; refer to
for details).
CLKM is routed to the MCU (pin 36 / TWCK0) where it may be used as timer input. The signal is filtered by a low-pass
filter to reduce harmonic emissions within the 2.4GHz ISM band. The filter is designed to provide a stable 1MHz clock
signal with correct logic level to a microcontroller pin with sufficiently suppressed harmonics. CLKM frequencies above
1MHz would require a redesign of R11 and C28 which in the current device are covered by the RF shield. In case of RC
cut-off frequency adjustments, depending on the specific load and signal routing conditions, one may observe
performance degradation of channel 26. Since its possible influence on the radio performance it is recommended to
disable CLKM output if not needed.
®
802.15.4, ZigBee, RF4CE, SP100 and high data rate ISM applications. It is tuned with the onboard 2.45GHz
Atmel AVR2030: ATRF231USB – Hardware User Manual [APPLICATION NOTE]
Appendix
C).
42018A−AVR−08/2012
[2]
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