Delay from GPIOTE Event until a Task is started over PPi on nRF52

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

MartinBL — Tue, 18 Apr 2017 13:59:38 GMT

Hi, as of now we actually don't have a good explanation why the nRF51 accepts higher frequencies than the nRF52. We need to do some simulations to figure that out, but unfortunately the designers are very busy these days and that might take a while. If this is of grave importance to you please open a support ticket on MyPage, link to this thread, and express your concerns there.

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

Pascal Künzi — Tue, 04 Apr 2017 05:50:17 GMT

Thanks Martin. That is "good" to know having my results confirmed. Yes, this does work properly on the nRF51 up to a frequency of 4MHz. The only difference I could find comparing the product specification is the additional 16MHz Latch in the PPI peripherals.

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

MartinBL — Mon, 03 Apr 2017 15:10:44 GMT

I believe I may have misunderstood the issue. I thought @Pascal Künzi was counting clock edges and somehow counted too many?

I talked to the designers and they said that one cannot expect to catch all the edges of a signal with higher frequencies than 2.66MHz on the nRF52. But are you saying that this worked on nRF51?

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

wizath — Sun, 02 Apr 2017 12:39:59 GMT

Hi, is there any new solution for this issue?

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

Pascal Künzi — Fri, 17 Feb 2017 07:13:58 GMT

Thank you for looking into that! I just tried your workaround but it didn't work. I varied the voltage from 2.5-3.2V but it didnt make a difference with either CONSTLAT on or off. At arround 2.6MHz the events aren't generated properly anymore. We are using the nRF52 in the QFN package on a custom pcb. The supply voltage is 3.3V and the HF-signal at the input GPIO looks as expected.

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

MartinBL — Thu, 16 Feb 2017 15:30:25 GMT

We have managed to reproduce the issue, but have not found the root cause. One workaround that seems to work (with a frequency generator) is to lower the signal voltage to ~0.2V below VDD. Can you please try this and tell me if it works?

PS: if you use a nRF52 DK kit there are some protection diodes in front of the chip reducing the input voltage a bit. So make sure to measure VDD_nRF and do not assume that your supply voltage is the same as the voltage supplied to the nRF52.

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

Pascal Künzi — Thu, 16 Feb 2017 13:43:31 GMT

Hi Martin. The nRF is supplied with 3.3V and the signal generator is an Agilent which does generate a sharp and proper 3.3V square signal.

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

MartinBL — Thu, 16 Feb 2017 12:38:21 GMT

Hi Pascal. What kind of signal generator do you use, what is the signal peak voltage, and the nRF52's supply voltage?

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

Pascal Künzi — Thu, 09 Feb 2017 07:43:04 GMT

Hi Ole,

Thanks for the input! Yes I do see a difference. The delay is reduced to the ~230ns which I also measured with the nRF51. But the nRF52 stil can't handle all the rising edges. It seems to me, that the cpu is not able to clear the event register before the next rising edge appears.

RE: Delay from GPIOTE Event until a Task is started over PPi on nRF52

Ole Bauck — Wed, 08 Feb 2017 13:10:47 GMT

Do you see any difference in the delay if you enable constant latency mode (NRF_POWER->TASKS_CONSTLAT = 1)?