STM32: create synchronious PWMs

[krebsbstn]

Describe the bug
Hi,
I am Working on a STM32-H7A3ZI-Q, trying to drive a TCD1304-Sensor.
Therefore it is needed to create at least two PWMs with 2MHz and 500KHz respectively.
The Datasheet of STM32-H7A3ZI-Q points out, that there is a possibility of Timer Link feature.

To get those PWMs synchronized to each other, I tried using the same Timer with different channels.
This is not working because the output signals will have the same frequency but different duty cycles.

Creating the two PWMs with different Timers they have a drift referring to each other.
As consequence the Timing requirements of TCD1304 cannot be held.

Without Zephyr you might have to drive the two Timers as Slaves of another Timer to get them synchronized.
Is there a Way to Synchronize the PWMs with the Device tree?

To Reproduce
create a new Project with the following contents for a STM-H7A3ZI-Q.
prj.conf

CONFIG_PWM=y
CONFIG_SYS_CLOCK_TICKS_PER_SEC=100

main.c

#define FM_PERIOD 2000000U
#define SH_PERIOD 500000U

void main(){
    /* Initialize and start PWM Signals */
    const struct device *fM_device = device_get_binding("FM");
    const struct device *SH_device = device_get_binding("SH");
    if (!fM_device | !SH_device){
        printk("TCM1304 - PWM initialize failed.");
        return;
    }
    pwm_set(fM_device, 1, FM_PERIOD, 0.5*FM_PERIOD, 0);
    pwm_set(SH_device, 4, SH_PERIOD, 0.5*SH_PERIOD, 0);
    while(1){
        ;
    }
};

nucleo_h7a3zi_q.overlay

...
&timers1 {
    st,prescaler = <10>;
    status = "okay";
    
    pwm1: pwm {
        status = "okay";
        label = "FM";
        pinctrl-names = "default";
        pinctrl-0 = <&tim1_ch1_pe9>;
    };
};

&timers4 {
    st,prescaler = <100>;
    status = "okay";

    pwm3: pwm {
        status = "okay";
        label = "SH";
        pinctrl-names = "default";
        pinctrl-0 = <&tim4_ch4_pd15>;
    };
};
...

Expected behavior
Seeing two synchronized PWMs on the both Pins.

Impact
It is not possible to drive complex Sensors with PWMs.

Environment (please complete the following information):

• OS: Linux
• Toolchain: Zephyr SDK
• STM32-CubeIDE

Additional context
The PWM Signals can be measured with an oscilloscope at the pins PE9 and PD15

[zephyrbot]

Hi @erwango,

This issue, marked as an Enhancement, was opened a while ago and did not get any traction. Please confirm the issue is correctly assigned and re-assign it otherwise.

Please take a moment to review if the issue is still relevant to the project. If it is, please provide feedback and direction on how to move forward. If it is not, has already been addressed, is a duplicate, or is no longer relevant, please close it with a short comment explaining the reason.

@krebsbstn you are also encouraged to help moving this issue forward by providing additional information and confirming this request/issue is still relevant to you.

Thanks!

[jpowen898]

@zephyrbot and @erwango Is this feature still in the works? I am working on an existing project using stm32's and we are wanting to switch zephyr in the near future but we the cascaded timer feature. Can you give me a timeline on when this would be implemented? Or is there a work around where I could access the stm32 hal directly and implement a temporary work around?

[erwango]

@jpowen898 This feature is not in our priority list. To access STM32 HAL directly from your application see https://github.com/zephyrproject-rtos/hal_stm32?tab=readme-ov-file#use-stm32cube-in-your-application