I.MX6 Piezo Buzzer Control with pwm_backlight?

[mukelarvin]

Hey everyone,

I'm trying to run a small CEM 1203 buzzer directly from one of the PWMs on my I.MX6. Is there a convenient way to change the period of a pwm-backlight platform device?

Thanks,

L.M.

[EricNelson · Accepted solution]

Hi Luke,

You can use this code to allow frequencies in the form of musical "notes" centered around middle-C:

     https://github.com/boundarydevices/linux-imx6/commit/63b106e30a42e5ee89c4c7d0644e853f013276db

If you name your platform device "buzzer", you can access the buzzer in sysfs like so:

~/$ echo -n C > /sys/class/leds/buzzer/note   # turn on middle C
~/$ echo -n ' ' > /sys/class/leds/buzzer/note # turn it off

[mukelarvin]

Hi Eric,

Thanks for the tip, I've updated the leds-pwm.c driver as you suggested but I'm not sure how to register the platform device.

I'm still on kernel 3.0.35 and all the examples I have use leds-gpio or pwm-backlight. I haven't had to add a platform device yet but looking at leds_pwm.h and other platform devices I came up with this:

static struct led_pwm  imx6_led_pwms[] = {
  {
  .name = "buzzer",
  .default_trigger = ,
  .pwm_id = 2,
  .active_low = ,
  .max_brightness = ,
  .pwm_period_ns = ,
  }
};


static struct led_pwm_platform_data imx6q_led_pwms_data = {
  .leds = imx6q_pwm_leds,
  .num_leds = ARRAY_SIZE(imx6q_led_pwms),
};


static struct platform_device imx6q_pwm_led_device = {
  .name = "leds-pwm",
  .id = 1,
  .num_resources = ,
  .dev = {
    .platform_data = &imx6q_led_pwms_data,
  }
};


static void __init imx6q_add_device_led_pwms(void)
{
  platform_device_register(&imx6q_pwm_led_device);
}

Could you help me fill in the blanks? Or point me towards an example?

[EricNelson]

Here's an example:

https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_4.1.0/arch/arm/mach-mx6/board...

[igorpadykov]

Hi Luke

please look at sect. 8.6 "Buzzer" below

Linux Software User Manual (i.MX6) - BlueWiki

Best regards

igor

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