Generating 50% duty cycle square waves greater than 1Mhz using PWM.

RE: Generating 50% duty cycle square waves greater than 1Mhz using PWM.

himothy — Thu, 29 Sep 2022 17:43:03 GMT

Thanks for the follow up Sigurd.

Setting the GPIO pin in high drive mode makes the waveform "more square." But a bit more of a clipped sine wave than a square wave. It also increases the amplitude too.

RE: Generating 50% duty cycle square waves greater than 1Mhz using PWM.

Sigurd — Thu, 29 Sep 2022 07:40:41 GMT

[quote user="himothy"]Would just like to confirm that 8Mhz is the highest frequency achievable.[/quote]

Yes, this is the highest you can get.

[quote user="himothy"]Is there any way to adjust the waveform shape so that the output is more square?[/quote]

Maybe if you set the GPIO pin in high drive mode.

nrf_gpio_cfg(pin_number, NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_DISCONNECT, NRF_GPIO_PIN_NOPULL, NRF_GPIO_PIN_H0H1, NRF_GPIO_PIN_NOSENSE);

[quote user="himothy"]Additionally, can the amplitude of the waveform be adjusted?[/quote]

No, it should be around ~VDD

RE: Generating 50% duty cycle square waves greater than 1Mhz using PWM.

himothy — Wed, 28 Sep 2022 20:15:17 GMT

Thanks for the help Sigurd. Very helpful and much appreciated.

Would just like to confirm that 8Mhz is the highest frequency achievable. There is no way to generate a higher frequency (16Mhz)?

I used the example you linked above and was able to generate a 8Mhz waveform.

Is there any way to adjust the waveform shape so that the output is more square? Additionally, can the amplitude of the waveform be adjusted?

RE: Generating 50% duty cycle square waves greater than 1Mhz using PWM.

Sigurd — Wed, 28 Sep 2022 11:49:20 GMT

[quote user=""]

1) What is the max frequency output achievable using PWM (is it 16Mhz)?

[/quote]

Using the PWM HW peripheral, then lowest allowed .top_value is 3, so the max frequency you can get with the PWM peripheral is 16(base or prescaler)/3(countertop) = 5.3333 MHz.

[quote user=""]2) How can I achieve this (or 8Mhz/16Mhz)? An example would be greatly appreciated.[/quote]

Using GPIOTE+TIMER+PPI, it possible to get max 8 MHz with duty ~50%. See e.g. this post: nRF52 clock in and out