Trouble with PWM on STM32 Blackpill V1.2 (STM32F401CCU6TR)

[Aditya-A-garwal]

Hey everyone! I am new to Zephyr, and decided to use the STM32 Blackpill to control servo motors and ESCs with PWM signals. To start, I wanted to use Timer 5 to generate PWM signals on all 4 channels. Eventually, I intend to use more timers and even capture PWM signals (from a flysky receiver). For a reason I can't seem to find, the pwm_set function is failing.

In the above image (taken from https://docs.zephyrproject.org/latest/boards/weact/blackpill_f401cc/doc/index.html), It says that we can use PA0...3 with Timer 5. This is also shown in the datasheet, along with the alternate function mode -

My devicetree overlay (boards/blackpillf401cc.overlay in the project directory) -

#include <zephyr/dt-bindings/pinctrl/stm32-pinctrl.h>

/ {

    leds {
        compatible = "gpio-leds";
        led_0: led_0 {
            gpios = < &gpioc 13 GPIO_ACTIVE_LOW >;
        };
    };
};

&pinctrl {

    tim5_ch1_pa0: tim5_ch1_pa0 {
        pinmux = < STM32_PINMUX('A', 0, AF2) >;
    };
    tim5_ch2_pa1: tim5_ch2_pa1 {
        pinmux = < STM32_PINMUX('A', 1, AF2) >;
    };
    tim5_ch3_pa2: tim5_ch3_pa2 {
        pinmux = < STM32_PINMUX('A', 2, AF2) >;
    };
    tim5_ch4_pa3: tim5_ch4_pa3 {
        pinmux = < STM32_PINMUX('A', 3, AF2) >;
    };
};

&timers5 {
    status = "okay";
    pwm5: pwm {
        compatible = "st,stm32-pwm";
        status = "okay";
        pinctrl-0 = < &tim5_ch1_pa0 &tim5_ch2_pa1 &tim5_ch3_pa2 &tim5_ch4_pa3 >;
        pinctrl-names = "default";
    };
};

My src/main.c file -

#include <stdio.h>

#include <zephyr/kernel.h>

#include <zephyr/drivers/gpio.h>
#include <zephyr/drivers/pwm.h>

static const struct gpio_dt_spec led0 = GPIO_DT_SPEC_GET(DT_NODELABEL(led_0), gpios);
static const struct device *pwm5_dev = DEVICE_DT_GET(DT_NODELABEL(pwm5));

int main(void) {

	if (!gpio_is_ready_dt(&led0)) {
		return 0;
	}
	if (gpio_pin_configure_dt(&led0, GPIO_OUTPUT_INACTIVE) < 0) {
		return 0;
	}

	// 5 fast blinks
	for (uint32_t i = 0; i < 5; ++i) {

		gpio_pin_set_dt(&led0, 1);
		k_msleep(50);
		gpio_pin_set_dt(&led0, 0);
		k_msleep(50);
	}

	if (!device_is_ready(pwm4_dev)) {
		return 0;
	}

	if (!device_is_ready(pwm5_dev)) {
		return 0;
	}

	// 5 slow blinks
	for (uint32_t i = 0; i < 5; ++i) {

		gpio_pin_set_dt(&led0, 1);
		k_msleep(400);
		gpio_pin_set_dt(&led0, 0);
		k_msleep(400);
	}

        // pwm_set returns non-zero value
	if (pwm_set(pwm5_dev, 1, PWM_USEC(1000), PWM_USEC(2500), PWM_POLARITY_NORMAL) != 0) {
		gpio_pin_set_dt(&led0, 1);
		return 0;
	}

	// 5 really slow blinks
	for (uint32_t i = 0; i < 5; ++i) {

		gpio_pin_set_dt(&led0, 1);
		k_msleep(1000);
		gpio_pin_set_dt(&led0, 0);
		k_msleep(1000);
	}

	for (;;);
}

I have tried it without the gpio led driver, and it still seems to fail. Can someone help me with this? I am completely stuck. I am using the following platform -

OS: Windows
Compiler: arm-none-eabi-gcc (version 12)
Runner: Openocd
Debugger: STLink

Appreciate all suggestions! Looking forward to contribute sensor drivers for some IMUs to Zephyr eventually.