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Diff between SP and ST (and use of SN)

0 votes
May somebody explain me the correct use of SP and ST params.
I've read the docs but I believe that I dont undestand it.

The docummentation sais:
SP stablish the periodo in wich de XBee module is in sleep mode (during sleep, the device is almost completely turned off and is sometimes incapable of sending or receiving data until it wakes up)

ST read time period of inactivity (no serial or RF data is sent or received) before activating Sleep Mode.

What the difference between them? (And what's their relationship with SN)

Thanks for your help
asked May 14, 2018 in IEEE 802.15.4 by sruedat New to the Community (6 points)

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1 Answer

+1 vote
SP determines how long the module will sleep until it checks for UART or RF that it needs to handle. If there is nothing to handle it goes back to sleep immediately.

If there is something to handle, the device will stay awake for the ST period (extended by any ongoing RF/UART traffic) before going back to sleep for the SP period.

SN is a multiplier on the SP period to allow for very long sleep cycles.
answered May 17, 2018 by jlovinger Veteran of the Digi Community (421 points)
Thanks for your help, now I have it clear.

However, this raises to me other question, How is possible to synchronize the readings of the ADC values of several nodes? ... I am developing a Python code and I have one doubts:

If the sleeping time is too big, synchronizing the readings is very complicated because one node can be in the begining of its sleep cycle when coordinator ask for its inputs (get_adc_value (IOLINE_IN_0), while other node could be in a more advanced time in its sleep cycle.

For instance, If I have ST and SP configured as documentation says:
Coord: SP = 28sg, ST = 15sg
End_device: SP = 25sg, ST = 15sg
Why Do I get several timeouts?

Does anyone know how to synchronize ADC readings from different nodes?
Thanks for your help.
While I haven't used it myself, my understanding is that DigiMesh (a special protocol developed by Digi) provides a built-in mechanism to synchronize wake/sleep cycles across multiple nodes.


If you want the same feature-set in ZigBee you would need to implement some sort of synchronization mechanism yourself.
Thanks, now it's all clear, It's a pity that my S2C modules only support asyncronous sleep modes (I've updated the firmware with DigiMesh but there aren't sync sleep modes abailable)
The only solution is use small SP cycles or better than that not use sleep modes.
Thank yo very much for your kind help