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RFST = CMD_DEMOD_TEST;
// Wait for modem to be running
while (RFRND == 0);
// Seed RNG
RNDL = RFRND;
RNDL = RFRND;
for (j=0; j<ARRAY_SZ; j++) {
// Read 8 random bytes into CRC generation
RNDH = RFRND;
RNDH = RFRND;
RNDH = RFRND;
RNDH = RFRND;
RNDH = RFRND;
RNDH = RFRND;
RNDH = RFRND;
RNDH = RFRND;
// Read out LSB of CRC state
rndarray[j] = RNDL;
}
// Shut down radio
while (RFST != 0);
RFST = CMD_SHUTDOWN;
// Restore LNA gain setting
LNAGAIN = lnagain_stored;
25.11 Packet Sniffing
Packet sniffing is a nonintrusive way of observing data that is either being transmitted or received. The
packet sniffer outputs a clock and a data signal, which should be sampled on the rising edges of the clock.
The two packet-sniffer signals are observable as GPIO outputs. For accurate time stamping, the SFD
signal should also be output. The packet sniffer does not work for the 2 Mbps data rate.
The packet-sniffer mode is selected in register MDMCTRL3.RFC_SNIFF_CTRL; see
description of the different modes of operation.
MDMCTRL3.RFC_SNIFF_CTRL
The packet-sniffer clock frequency is equal to the RF data rate. The data is output serially, in the received
or transmitted order. It is possible to use a SPI slave to receive the data stream.
When a complete packet has been transferred, the packet sniffer appends a status byte that tells which
value of the FREQCTRL register was used and if it was a TX or RX packet (bit 0 is high if it was a TX
packet). The appended byte is formatted as follows (first transmitted bit to the left):
FREQ(6)
This allows for the external receiver to differentiate between RX and TX packets.
SWRU191F – April 2009 – Revised April 2014
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Table 25-22. Packet-Sniffer Modes of Operation
00
Packet sniffer disabled
Data output from BSP. TX data, including CRC, is whitened if the whitener is
01
enabled. RX data, including CRC, is always de-whitened.
Data output from modulator. Only TX data before whitening is output. Any CRC
10
bytes are 0.
11
Data output from the demodulator. Only RX data before de-whitening is output.
FREQ(5)
FREQ(4)
FREQ(3)
Figure 25-14. Complete Appended Packet
Copyright © 2009–2014, Texas Instruments Incorporated
Description
FREQ(2)
FREQ(1)
FREQ(0)
CC2541 Proprietary Mode Radio
Packet Sniffing
Table 25-22
for a
TX
R0015-01
319
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