Figure 17: Power profile for low power listening mode where no frame is received
4.4.1 Configuring low-power listening
Configure the receiver parameters for channel, data rate, PRF, preamble code, etc. as required for normal
receive operation. Then enable and configure the Low-Power Listening functionality as follows:
Set ARXSLP (after RX automatically sleep) bit in Sub-Register 0x36:04 – PMSC_CTRL1.
Set preamble detect timeout (RX ON time) in Sub-Register 0x27:24 – DRX_PRETOC.
Set SNOZ_TIM (snooze time) field of Sub-Register 0x36:0C – PMSC_SNOZT.
Set SNOZE (snooze enable) bit in Sub-Register 0x36:04 – PMSC_CTRL1.
Set SLEEP_TIM (sleep time period) field in Sub-Register 0x2C:06 – AON_CFG0.
Set SLEEP_EN (sleep enable) field in Sub-Register 0x2C:06 – AON_CFG0.
Set WAKE_CNT (wake when sleep counter elapses) field in Sub-Register 0x2C:06 – AON_CFG0.
Set ONW_RX (on wake turn on the receiver) bit in Sub-Register 0x2C:00 – AON_WCFG.
Set ONW_LDC (on wake load configurations) bit in Sub-Register 0x2C:00 – AON_WCFG.
Set PRES_SLEEP (preserve sleep) bit in Sub-Register 0x2C:00 – AON_WCFG.
Set only MRXFCG bit in Register file: 0x0E – System Event Mask Register.
Set the RXENAB bit in Register file: 0x0D – System Control Register.
The DW1000 will then begin the low power listening, and will only generate an interrupt when a frame is
received. Frame filtering can be enabled to further restrict the interrupt to only be generated when a
correctly addressed frame is received. To save power in such a system the host microprocessor (if
sufficiently capable) can enter a low power state awaiting the DW1000 interrupt to wake it when a frame
arrives.
When a frame is received, low-power listening must be deactivated by clearing the ARXSLP bit before the
RXFCG interrupt is cleared. This is required to ensure that the DW1000 does not go back to sleep as soon as
the interrupt is cleared, which would prevent the user from reading the frame data correctly. Once the
received frame has been handled, low-power listening mode can be reactivated by setting the ARXSLP bit
once more and putting the DW1000 back into reception or sleep mode.
4.5 Low-Power SNIFF mode
Low-Power SNIFF mode is a lower power preamble hunt mode, also known as pulsed preamble detection
mode (PPDM), where the receiver (RF and digital) is sequenced on and off rather than being on all the time.
These on and off times are configurable in Register file: 0x1D – SNIFF Mode, and have default values of zero,
RX
IDLE
INIT
GO2SLP
Sample Wakeup Event:
Sleep counter expires
SLEEP SLEEP
2 RX attempts with no RX detected,
Host RX End.
WAKEUP
CLKPLL locked
Crystal stable,
RSTn=1
RX
Preamble
Timeout in PACs
Snooze Count (Reg:36.0c)
(in 19.2MHz cycles)
SNOOZE
IDLE
PLL Lock
Time (~5uS)
INIT
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