Clarification about mNumGrantGlitch coex counter

[hemanth-silabs]

@jwhui @abtink Can you please clarify the purpose of mNumGrantGlitch field in otRadioCoexMetrics? My understanding is that this indicates the number of times grant was asserted without request. Is my understanding correct?

[abtink]

@hemanth-silabs From my side I don't know enough about coex to be able to help you on this.

Generally the coex is delegated to the radio platform. OT stack itself is not involved it. The addition of otRadioCoexMetrics is only intended so that some helpful info (set of coex related counters) can retrieved from radio platform and passed through CLI and NCP.

[romacdon]

Thanks @abtink - @zhanglongxia it looks like you are the originator of otRadioCoexMetrics. Do you recall what you had in mind for the mNumGrantGlitch field?

[hemanth-silabs]

@jwhui @zhanglongxia any additional updates on this. The documentation around this field is not very descriptive and we are wondering how to maintain this.

[zhanglongxia]

Hi hemanth-silabs. In general, when the GRANT pin enters the active state, we assume that the Thread radio should be able to transmit or receive. But sometimes, the GRANT pin will quickly leave the active state after entering the active state. We consider this case as the GrantGlitch. This case has the same effect as GRANT pin not active.

[Irving-cl]

Hi @hemanth-silabs,

Glitch referes to the cases where the grant pin was unintentionally set to a different value for a very short time. In these cases, the handler will be triggered but the handler will see that the grant pin value doesn't change so the handler won't take any action.

[hemanth-silabs]

Thanks for your response @zhanglongxia @Irving-cl. Can you elaborate on what is considered as quick/short time? Should we consider any abort happening after the GRANT is active as glitch as well? Should we define min grant time, below which abort is considered glitch?

[zhanglongxia]

We generally use a GPIO interrupt to monitor the GRANT pin. We will check the GRANT pin's state in the interrupt function, if GRANT pin's state doesn't match the interrupt edge settings, we think a GrantGlitch happened. The Coex metrics are implemented in the platform layer, the min grant time can be defined by the platform developers.

[hemanth-silabs]

Thanks for the inpurs @zhanglongxia @Irving-cl. I will close this discussion.