decaWave DW1000 - Figure 19: Power Profile for Sniff; Figure 20: Power Profile for Sniff; Received

DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 43 of 242
should always be 1 less than the desired total. The off duration is programmed in units of 1 µs. When both
on and off durations are programmed with non-zero values SNIFF will be operational from the next RX
enable.
As an example if the PAC size is 8 symbols, (this is approximately 8 µs), and we want to have a 50:50 on-off
duty cycle, then we could set SNIFF_ONT to its minimum of 2 PAC intervals (by programming the counter
with a value of 1) and the SNIFF_OFFT to a value of 16 µs.
Figure 19 shows the power profile associated with SNIFF mode where the IC wakes up from SLEEP and
progress into the repeated IDLE-RX-IDLE-RX… duty-cycle of the pulsed preamble detection mode. A timeout
ends this and the DW1000 is returned to SLEEP.
Figure 19: Power profile for SNIFF where a frame is not received
Figure 20 shows a power profile for SNIFF mode, similar to Figure 19, except in this case preamble is
detected on the second period of RX sampling, and the DW1000 completes the reception of a frame.
Figure 20: Power profile for SNIFF where a frame is received
4.5.2 Low duty-cycle SNIFF mode
In Low duty-cycle SNIFF mode, where the off time is larger, the DW1000 can be configured to spend this off
time in the INIT state which is lower power than the IDLE state (used for the off period of a SNIFF). This is
enabled by setting the ARX2INIT bit in Sub-Register 0x36:04 – PMSC_CTRL1, in addition to configuring the on
and off times, SNIFF_ONT and SNIFF_OFFT, in Register file: 0x1D – SNIFF Mode. This instructs the receiver to
go to the INIT state for the off period of the Low-Power SNIFF mode.
RX
IDLE
INIT
GO2SLP
Sample Wakeup Event:
Sleep counter expires
SLEEP SLEEP
Frame Wait Timeout,
Host RX End.
WAKEUP
CLKPLL locked
Crystal stable,
RSTn=1
RX RX
IDLE IDLE IDLE
Configure RX Sniff Mode
Sniff On Time
(in PACs)
Sniff Off Time
(in uS)
RX
IDLE
INIT
Sample Wakeup Event:
Sleep counter expires
SLEEP
Interrupt Set
RX OK
WAKEUP
CLKPLL locked
Crystal stable,
RSTn=1
RX
(demod)
IDLE
IDLE
Configure RX Sniff Mode
Sniff On Time
(in PACs)
Sniff Off Time
(in uS)
Preamble
Detected
Host Activity
Read RX buffer