CC1352P7: PWM in Zephyr with GP Timers seems to be irregular

Ayush Singh

Part Number: CC1352P7

Tool/software:

I am trying to use PWM on my Beagleconnect Freedom running Zephyr. To test this, I am trying to fade LED similar to the Fade arduino sample. I have created a reproducible Zephyr sample application here.

I am using the following device tree overlay to enable PWM as stated in ti,cc13xx-cc26xx-timer-pwm:

```

/ {
aliases {
pwm-led0 = &pwm_led0;
};

pwmleds {
compatible = "pwm-leds";
pwm_led0: pwm_led_0 {
pwms = <&pwm0 0 255 PWM_POLARITY_NORMAL>;
label = "PWM MB1";
};
};
};

&pinctrl {
pwm0_default: pwm0_default {
pinmux = <17 IOC_PORT_MCU_PORT_EVENT1>;
bias-disable;
drive-strength = <2>;
};
};

&gpt0 {
status = "okay";
};

&pwm0 {
status = "okay";
pinctrl-0 = <&pwm0_default>;
pinctrl-names = "default";
};

```

What I observe is erratic blinking rather than smooth fade. It seems like the timing of the pulses is wrong or something. However, I do not have an oscilloscope to really test the output.

over 1 year ago

0 Marie H over 1 year ago

TI__Guru* 82431 points

Hi Ayush,

We don't have any examples with Zephyr so it's limited how we can support you with using it.

If you suspect the timing is wrong, maybe it would be helpful to compare the period scales? Per default the TI PWM driver uses a 1 Hz period but it's possible to change this with the pwmParams.

https://dev.ti.com/tirex/explore/content/simplelink_cc13xx_cc26xx_sdk_7_41_00_17/docs/drivers/doxygen/html/_p_w_m_8h.html

Cheers,

Marie H

+1 Devansh Tanna over 1 year ago

TI__Prodigy 50 points

In the main function, by using k_sleep(K_FOREVER) which puts thread into suspended mode so instead by using blocking statement like while (1); makes PWM driver work properly.

int main(void) {
    int i;


    pwm_set_pulse_dt(&pwm_led0, pwm_led0.period / 2);
    const struct pwm_cc13xx_cc26xx_config* config = pwm_led0.dev->config;

    while (1);
    // k_sleep(K_FOREVER);
    return 0;
}

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CC1352P7: PWM in Zephyr with GP Timers seems to be irregular