PWM options when using FreeRTOS and SoftDevice

RE: PWM options when using FreeRTOS and SoftDevice

Susheel Nuguru — Tue, 21 Apr 2020 13:24:36 GMT

[quote user="Aurel"]Isn't it more appropriate to use a custom hardware timer for low power pwm ?[/quote]

To achieve proper low power and accurate PWM it would be appropriate to use a custom hardware timer. For some this choice is not an option due to cost/complexity reasons.

RE: PWM options when using FreeRTOS and SoftDevice

Aurele — Tue, 21 Apr 2020 10:24:54 GMT

Hello,

Is it advised to use low power PWM with FreeRTOS ? I'm asking because i know this is a software pwm and it is using app_timer that is using xTimerTask. All FreeRTOS timer handler are called from a task context. Isn't it more appropriate to use a custom hardware timer for low power pwm ?

Regards,

Aurélien

RE: PWM options when using FreeRTOS and SoftDevice

Susheel Nuguru — Mon, 06 Jan 2020 08:53:08 GMT

Sorry for the late reply, just came back from the holidays.

The low power PWM does have automated change of duty cycle like softblink. App needs to wakeup in timer callbacks and do the change using low_power_pwm_duty_set

RE: PWM options when using FreeRTOS and SoftDevice

Tim Adu — Fri, 20 Dec 2019 14:03:40 GMT

Thank you Susheel,

I got it to work. One last question: how would you go about implementing a LED fade in/out pattern?
The LED softblink library made it easy by having a duty_cycle_step parameter. Is there a way to do it with the Low power PWM?

RE: PWM options when using FreeRTOS and SoftDevice

Susheel Nuguru — Fri, 20 Dec 2019 11:48:24 GMT

Hi Adu,

Softblink is a simple library mainly used for LED softblink application and it internally uses low power PWM.

APP PWM uses PPI/GPIOTE and few other resources to abstract more functionality to the app.

For your use case using low power pwm seems to fit fine even though you are using FreeRTOS. Just remember that you need to include app_timer_freertos.c instead of app_timer.c in your project as low power pwm library uses app_timer.