Sleepy node - data transmission time over thread

[Rajendra]

Hello there,

I have developed a board with nRF52840 and a sensor. My hardware and tools setup is:

SDK: nRF5_SDK_for_Thread_v0.10.0_e1c3d11

Thread version:OPENTHREAD/g6a15261b-dirty

THREAD Border Router = nRF52840 dev kit. Firmware is based on simple_coap_server.

Sleepy node = self designed board. Firmware is based on simple_coap_client.

 

I have few of questions related to THREAD networking:

 

1. My observation is, the nRF52840 sleepy node takes around 300 millisec to establish connection with Router. Is this expected time?

2. After calling otCoapSendRequest() it takes around 150 millisec to actually send the packet on Radio. Interestingly, this time is directly proportional to the range covered. In other words, for 70 millisec, the range covered is about 5 meters. If this time is set to 150 millisec, range covered is about 12 meters.

 

3. It takes around 60 millisec to complete rest of the activities such as initialization and sensor data reading. Summing up everything, the ON time is around 60+300+150 = 510 millisec. Is this expected ON time for THREAD sleepy node?

Thanks,

Rajendra

[Kamil Sroka]

1. This time will be highly non-deterministic. Simple attachment to Thread network can take from 0,2s to 5s and is affected by air traffic, random jitters, or other non-deterministic factors defined in the Thread protocol. You can find some of those times in table on this page: http://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.threadsdk.v0.11.0%2Fthread_multiprotocol.html
2. Range is not connected with time needed to send the packet - this looks like a coincidence.
3. Thread SED has its radio powered off most of the time so it is better to call __WFE() and keep everything asynchronous rather then use SYSTEMOFF

Can you share a piece of code to reproduce this?

[Rajendra]

Thank you Kamil for answer, it would really help.