iOKE868 LoRaWAN® /
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User Manual Version: 1.0
Page 9 of 12
Real Time Clock Synchronization
The iO881A features an embedded Real Time Clock ( RTC ) which is used to schedule several Calendar Events for meter reading and other
functionalities. For proper operation it is highly recommended to synchronize the RTC. The initial synchronization can be done by means of
the WS-Configurator PC-Tool. On every synchronization the current time stamp is stored in the none volatile memory of the iO881A. After a
power-cycle or system reset this stored value is used to inititalize the RTC. If the value is invalid or less than 01.01.2000 00:00:00 the RTC
will start at 01.01.2000 00:00:00.
After startup the device starts with a LoRaWAN activation procedure ( OTAA or ABP ) and initiates a LoRaWAN uplink MAC command to
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get the current data and time from the LoRaWAN server. On success the received value is used to configure the RTC and is finally stored in
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the NVM for later usage after a system reset.
Due to the fact that some LoRaWAN server do not support the "Get Time MAC Command" a fall back mechanism is implemented. In case of
no MAC command response the firmware transmits a "Get Date Time Request" application command via LoRaWAN to the connected
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Application Server which might be able to answer this request. This request is transmitted 5 times.
The new "Get Date Time Request" looks as follows;
LoRaWAN Port: 32
LoRaWAN Payload Syntax:
Request < Get > < Resource ID >
Example:
< Get > < DateTime >
< 01 > < 01 >
h
h
The corresponding Get Date Tiime response must look like this:
LoRaWAN Port: 32
LoRaWAN Payload Syntax:
Response < Get Response > < Resource ID > < data >
Example:
< Get Response > < DateTime > < current date time as seconds since 01.01.1970, 00:00:00 as
32-Bit integer, LSB first , e.g.:
unsigned
"2020-09-18 11:46:33 >
< 02 > < 01h > < ( 19 9E 64 5F ) >
h
h
Due to the fact that the clock crystal frequency can drift over temperature it is recommended to synchronize the RTC via
LoRaWAN from time to time ( e.g. once per week ).
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