gpiote event -> ppi -> gpiote task latency

RE: gpiote event -> ppi -> gpiote task latency

Susheel Nuguru — Fri, 18 Aug 2023 13:28:50 GMT

[quote user="victor passe"]hi, thanks for your awnser, constant latency is the first line of my code.
is there anything else i must to to enable constant latency?
i can not get under 360-380ns[/quote]

Unfortunately there is no documentation that describes the path delay for events between peripherals.

[quote user="victor passe"]how does errata [156] play in to this?[/quote]

It is very likely that this errata is effecting in your case as you are using TASK_CLR. Are you seeing any power consumption increase? if not, then this errata does not effect you.

[quote user="victor passe"]i also tested this:
*(volatile uint32_t *)(NRF_GPIOTE_BASE + 0x600 + (4 * GPIOTE_OC)) = 1;
now it is one clock cycle faster (~330ns), is there any way i could get any documentation of these type of "hidden" registers?[/quote]

I do not have access to hidden registers that are not published. Using them in any other way than the way published is very dangerous and can cause unpredictable behavior.

RE: gpiote event -> ppi -> gpiote task latency

victor passe — Wed, 16 Aug 2023 09:06:20 GMT

hi, thanks for your awnser, constant latency is the first line of my code.
is there anything else i must to to enable constant latency?
i can not get under 360-380ns

i also tested this:
*(volatile uint32_t *)(NRF_GPIOTE_BASE + 0x600 + (4 * GPIOTE_OC)) = 1;
now it is one clock cycle faster (~330ns), is there any way i could get any documentation of these type of "hidden" registers?

how does errata [156] play in to this?
I tried to use only odd, only even and changed tasks_clr -> tasks_out but no change in latency.
I can do not see any difference with constant latency or with low power. the fact that those are the same implies that i do not enter both, right? can i see what mode the nrf52805 is in?

RE: gpiote event -> ppi -> gpiote task latency

Susheel Nuguru — Tue, 08 Aug 2023 13:17:54 GMT

Yes, it is the path that the signal needs to take and to be sampled. The best case scenario is 1 clock cycle propagation of the event in interest thought a peripheral and worst case is 2 cycles.

I think I have seen similar propagation/sampling delays similar to your configuration in this thread. Try to see if enabling the constant latency in the power have any better results in your case.

RE: gpiote event -> ppi -> gpiote task latency

victor passe — Tue, 08 Aug 2023 09:45:50 GMT

or am i limited by gpio (1cycle) + gpiote (1cycle) + ppi (1cycle) + gpiote (1cycle) + gpio (1cycle) = 5-6 cycles = 380ns?