Setup Input Capture in Zephyr

RE: Setup Input Capture in Zephyr

Håkon Alseth — Fri, 23 Apr 2021 06:32:41 GMT

[quote user="moose"]Any plans to enable the input capture feature of the zephyr PWM driver?[/quote]

There's no natural way of implementing this into the driver, without depending on other drivers and external setup.

[quote user="moose"]The event can be either HItoLO, LOtoHI, or TOGGLE. The toggle event would have worked except when we route it through a PPI channel to a timer capture register; either transition will update the capture register. Any idea on how to do this? Thx![/quote]

Connect the signal to two GPIOs, one that is configured hitolow, and the second that is configured lotohi.

Kind regards,

Håkon

RE: Setup Input Capture in Zephyr

moose — Fri, 23 Apr 2021 05:39:56 GMT

Thank you for the info. Any plans to enable the input capture feature of the zephyr PWM driver?

Meanwhile, we have created the code to capture the time associated with input signal transitions referencing the nrfx example you shared. We got it working, but it is not exactly what we want. We need to capture the time of both the rising and falling edges of the same input signal. It looks like we can only generate one event per GPIO pin. The event can be either HItoLO, LOtoHI, or TOGGLE. The toggle event would have worked except when we route it through a PPI channel to a timer capture register; either transition will update the capture register. Any idea on how to do this? Thx!

RE: Setup Input Capture in Zephyr

Håkon Alseth — Wed, 21 Apr 2021 12:00:18 GMT

Hi,

The PWM port for nrf devices does not have capture capabilities:

https://github.com/nrfconnect/sdk-zephyr/blob/master/drivers/pwm/pwm_nrfx.c#L263-L266

Thus it will return an error code if you try to call _capture() call:

https://github.com/nrfconnect/sdk-zephyr/blob/master/include/drivers/pwm.h#L221

The functionality you are after must be implemented using a TIMER, GPIOTE IN, and PPI, something like this one for nrf53/nrf91 (note: uses dppi, while the nrf52-series have ppi):

https://github.com/Rallare/fw-nrfconnect-nrf/blob/nrf9160_samples/samples/nrf9160/nrfx_timed_signal/src/main.c

Kind regards,

Håkon