ST STM32WL5 Series User Manual

Sub-GHz radio (SUBGHZ) RM0453
180/1461 RM0453 Rev 1
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 RxPeriod +SleepPeriod. 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 RxPeriod + 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 μs (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 RxPeriod + SleepPeriod
• LoRa modulation: T
preamble
+ T
header
< 2 x RxPeriod + SleepPeriod
Figure 17. Receiver listening mode timing
0123456
Opcode RxPeriod[23:0] SleepPeriod[23:0]
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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 μs
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 RxPeriod + SleepPeriod
RxPeriod
Preamble detection
Save
context

ST STM32WL5 Series Specifications

General

Brand	ST
Model	STM32WL5 Series
Category	Microcontrollers
Language	English