GPIOLED in the FreeBSD on the Raspberry Pi

FreeBSD supports GPIOLED(4).
Here is a description how to work with it on the Raspberry Pi (for example).

GPIOLED(4) is a special driver attaches a led(4) device to a GPIO pin.
After describing physical led as a gpioled(4) we control it through a led(4) device.

Raspberry Pi has one gpioled by default. This is a led “ACT” near audio output.

This led described in the file rpi.dts:

314         leds { 
315                 compatible = "gpio-leds"; 
316  
317                 ok { 
318                         label = "ok"; 
319                         gpios = <&gpio 16 1>; 
320  
321                         /* Don't change this - it configures 
322                          * how the led driver determines if 
323                          * the led is on or off when it loads. 
324                          */ 
325                         default-state = "keep"; 
326  
327                         /* This is the real default state. */ 
328                         linux,default-trigger = "default-on"; 
329                 }; 
330         };

This led has name “ok”. Default state for this led is “keep”. This mean that it is “on” in normal state.
To work with this led we can use device /dev/led/ok.

To turn it off we can use this command:

# echo 1 > /dev/led/ok

And to turn it on we can use this command:

# echo 0 > /dev/led/ok

We can use symbols “*”, “-“, “0”, “1”, “f”, “f1” … “f9” and so on as described in the manual page led(4).

Let’s connect usual LED to GPIO pin 25:

LED25

To describe it as GPIOLED we need to add this four strings to the file /usr/src/sys/boot/fdt/dts/arm/rpi.dts:

led25 {
	label = "led25";
	gpios = <&gpio 25 0>;
};

gpioled

After changing the rpi.dts file, we need to compile it:

# cd /usr/src/sys/tools/fdt
# setenv MACHINE arm
# ./make_dtb.sh /usr/src/sys /usr/src/sys/boot/fdt/dts/arm/rpi.dts rpi.dtb

Then we need to copy the result to the directory /boot/msdos:

# cp /boot/msdos/rpi.dtb /boot/msdos/rpidtb.old
# cp rpi.dtb /boot/msdos

dtb

The new rpi.dtb less than the old one but it works.

Let’s play with our leds:

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7 thoughts on “GPIOLED in the FreeBSD on the Raspberry Pi

  1. FreeBSD rpi 11.0-CURRENT FreeBSD 11.0-CURRENT #0 r278908: Tue Feb 17 23:25:47 UTC 2015
    RPi Model B+

    dmesg shows: gpioled0: at pin(s) 16 on gpiobus0

    # echo 1 > /dev/led/ok
    # echo 0 > /dev/led/ok

    has no effect on the ACT LED, no does:

    # gpioctl 16 0
    # gpioctl 16 1

    gpioctl -lv shows the state as changing but the ACT LED does not light at all (it lights when rebooting for a second so the LED does work).

  2. No luck with pin 47 :

    #gpioctl -f /dev/gpioc0 -t 47
    gpio_pin_toggle: Invalid argument

    #gpioctl 47 1
    gpio_pin_set: Invalid argument

    I suspect the FreeBSD tweaks for the Model B+ were simply to get FreeBSD running with the new USB/LAN chip and that my dmesg entry of:

    gpioled0: at pin(s) 16 on gpiobus0

    indicates that the rpi.dts file was not updated for the B+. I’ll see if I can find the dts file used in the FreeBSD svn.

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