The application will automatically join a LoRaWAN network (see configuration).
Once a network is joined (i.e. when the corresponding event is triggered), the configured time synchronization service is initialized by calling smtc_modem_time_set_sync_interval_s() and launched by calling smtc_modem_time_start_sync_service(). Then, time synchronization requests are sent on a regular basis by this service. The service can be stopped anytime by calling smtc_modem_time_stop_sync_service().
The application also implements an asynchronous time synchronization request, based on the LoRa Basics Modem alarm functionality. Each time the alarm-related event is triggered, the application sends a time synchronization request by calling smtc_modem_time_trigger_sync_request().
For more information:
- MAC command: refer to the LoRaWAN specification v1.0.4
- ALC sync: refer to the LoRa Developer portal.
Several parameters can be updated in main_time_sync.h header file:
| Constant | Description | Possible values | Default Value | Note |
|---|---|---|---|---|
APP_MODEM_TIME_SYNC_SERVICE |
Select the time synchronization service | Value in smtc_modem_time_sync_service_t |
SMTC_MODEM_TIME_MAC_SYNC |
|
APP_MODEM_TIME_SYNC_INTERVAL_IN_S |
Interval in second between two automatic time synchronization request | uint32_t |
900 | |
APP_MODEM_TIME_MANUAL_SYNC_INTERVAL_IN_S |
Interval in second between two manual time synchronization request | uint32_t |
130 | Set to 0 to disable it |
When compiling with arm-none-eabi-gcc toolchain, all these constant are configurable through command line with the EXTRAFLAGS.
See README.md.
Here follow the steps that shall be seen in the logs to indicate the expected behavior of the application:
INFO: Modem Initialization
INFO: ===== LoRa Basics Modem time synchronization example =====
INFO: ###### ===== BASICS MODEM RESET EVENT ==== ######
Following this print you shall find application and parameter prints
At first run no time is supposed to be available
INFO: ###### ===== JOINED EVENT ==== ######
INFO: Checking/printing local UTC time joining network
WARN: No time available.
INFO: ###### ===== TIME EVENT ==== ######
Time: SMTC_MODEM_EVENT_TIME_VALID
INFO: Checking/printing local UTC time upon TIME reception
INFO: Current UTC time: Tue 2022-04-05 20:27:49 GMT
If APP_MODEM_TIME_MANUAL_SYNC_INTERVAL_IN_S is set to any other value than 0 an alarm event is supposed to be seen in the logs as follows:
INFO: ###### ===== ALARM EVENT ==== ######
INFO: Sending synchronization request upon manual timer request
Manual time synchronization request done. Next manual request in 130 seconds.