PWM consumed power

RE: PWM consumed power

Sigurd — Wed, 06 Jun 2018 07:37:17 GMT

Hi,

[quote user="Jim_guo"]but the current of method 1 is large, is this normal?[/quote]

What did you measure? Updates of duty cycle values will require the EasyDMA to be active, adding about 1.2 mA to the current consumption, but the updates can be done without CPU intervention.

[quote user="Jim_guo"]If I need to output a 6-cycle pulse with a fixed duty cycle on an IO port, do I not need to use easyDMA and the current will be smaller?[/quote]

I believe that is correct, with a fixed constant duty cycle value, the PWM peripheral will draw less current. I did a quick test here, and measured around 400µA for that scenario.

RE: PWM consumed power

Jim — Mon, 04 Jun 2018 09:28:41 GMT

Thanks for your instant reply!

I tested the pwm_driver example. Method 1 drives the GPIO to generate irregular waveforms by using the PWM_driver method. The second method is to timer (NRF_DRV_TIMER_INSTANCE, constantly adjusting the length of the timer) to interrupt the flip GPIO port. The waveforms output by Method 1 and Method 2 are very Accurate, but the current of method 1 is large, is this normal?
If I need to output a 6-cycle pulse with a fixed duty cycle on an IO port, do I not need to use easyDMA and the current will be smaller?

RE: PWM consumed power

Sigurd — Mon, 04 Jun 2018 08:58:47 GMT

Hi,

Generally, the PWM driver will draw some more current due to the EasyDMA logic, but the PWM driver is very flexible, and the built-in decoder and EasyDMA capabilities make it possible to manipulate the PWM duty cycles without CPU intervention.

What examples in the SDK did you test? pwm_driver and pwm_library?

What results did you get?

Note that the PWM library example in the SDK is not power optimized(uses nrf_delay_ms() that will keep the CPU active)