
Sub-GHz radio (SUBGHZ)
RM0453
180/1454
RM0453 Rev 2
The following steps are performed:
1.
Save sub-GHz radio configuration.
2. Enter Receive mode and listen for a preamble for the specified RxPeriod period.
3. Upon the detection of a preamble, the RxPeriod timeout is stopped and restarted with
the value 2 x RxSleepPeriod. During this new period, the sub-GHz radio looks
for the detection of a synchronization word when in (G)FSK modulation mode, or a
header when in LoRa modulation mode.
4. If no packet is received during the listen period defined by 2 x Rx SleepPeriod,
the Sleep mode is entered for a duration of SleepPeriod. At the end of the receive
period, the sub-GHz radio takes some time to save the context before starting the sleep
period.
5. After the sleep period, a new listening period is automatically started. The sub-GHz
radio restores the sub-GHz radio configuration and continuous with step 2.
The listening mode is terminated in one of the following cases:
•
if a packet is received during the listening period: the sub-GHz radio issues a RxDone
interrupt and enters Standby mode.
•
if
SetStandby()
is sent during the listening period or after the sub-GHz has been
requested to exit Sleep mode by sub-GHz radio SPI NSS
Receive period duration is computed as follows:
Receive period duration = RxPeriod x 15.625
μ
s (max receiver duration = 262.14 s)
Sleep period duration is computed by the following formula:
Sleep period duration = SleepPeriod x 15.625 us (max sleep duration = 262.14 s)
For correct operation, the following must be respected:
•
(G)FSK modulation: T
preamble
+ T
syncword
< 2 x Rx SleepPeriod
•
LoRa modulation: T
preamble
+ T
header
< 2 x Rx SleepPeriod
Figure 17. Receiver listening mode timing
0
1
2
3
4
5
6
Opcode
RxPeriod[23:0]
SleepPeriod[23:0]
w
w
w
w
w
w
w
byte 0
bits 7:0
Opcode
: 0x94
bytes 3:1
bits 23:0
RxPeriod[23:0]
: Receive duration
0x000000: Receiver duration disabled, receiver remaining active until a
packet is detected
0x000001 - 0xFFFFFF: Receive duration, resolution 15.625
μ
s
bytes 6:4
bits 23:0
SleepPeriod[23:0]
: Sleep duration, resolution 15.625
μ
MSv62623V1
Standby and SF
Sub-GHz radio
mode
Sleep
RX
Sleep
2 x Rx SleepPeriod
RxPeriod
Preamble detection
Save
context