Generating 8MHz clock signal using compatible = "pwm-clock" node on Zephyr

RE: Generating 8MHz clock signal using compatible = "pwm-clock" node on Zephyr

Einar Thorsrud — Wed, 11 Dec 2024 11:35:16 GMT

Hi Fernando,

I was incorrect in my previous reply. You cannot generate an 8 MHz output using the PWM peripheral (the maximum is limted to 5.3333 MHz as explaiend in this post). It is possible to generate an 8 MHz putput though, by using a timer and GPIOTE connected via PPI. That can be done as shown in this post.

Einar

RE: Generating 8MHz clock signal using compatible = "pwm-clock" node on Zephyr

Fernando Fontes — Fri, 06 Dec 2024 14:39:01 GMT

Hi,

Thank you for the reply.

I don't have the oscilloscope with me right now but declaring tdc_clk_in as compatible = "pwm-clock" only allows me to reach frequencies up to 1MHz.

I've used the function pwm_set_dt(&tdc_clk_in,PWM_HZ(1000000),PWM_HZ(1000000) / 2); and it worked. However with pwm_set_dt(&tdc_clk_in,PWM_HZ(8000000),PWM_HZ(8000000) / 2); it does not.

In the Zephyr pwm-clock documentation they mention a 1MHz internal clock signal, not sure if that is the maximum that I can reach. They also mention that I might need to change prescaler options for different settings.

Thanks in advance,

Fernando

RE: Generating 8MHz clock signal using compatible = "pwm-clock" node on Zephyr

Einar Thorsrud — Fri, 06 Dec 2024 14:30:46 GMT

Hi,

There should not be any problems using 8 MHz PWM. How are you measuring the output signal? Can you share the plot? Using the PWM is also covered in a DevAcademy course, here.