Default value of RGB LEDs

Discussion around products based on ARM Cortex-A5 core.

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Joined: Fri May 01, 2020 6:05 pm

Default value of RGB LEDs

Sat Jul 18, 2020 12:49 am


I am using the SAMA5D27 SOM1 EK board, to help in development of a board which uses the SAMA5D27 chip.

I am trying to set the brightness of LEDs PA31 and PB1, which are set as PWM LEDs in the DTS.
I have used the pwm-leds configuration in the DTS, and pinmuxed PA31 and PB1 as PWML0 and PWML1 respectively.

When I flash the microchip-headless-image to the board, and once the board boots up, the RGB LEDs turn on. However, when I check the brightness value of the LEDs in /sys/class/leds/<led_name>/brightness, they all show as 0, even though PA31 and PB1 are both visibly on.

I then try to switch off the LEDs, by entering the following command :

Code: Select all

> echo 0 > /sys/class/leds/<led_name>/brightness 
This does not turn the LED off.

However, if I change the value to any value except 0, by entering for example :

Code: Select all

> echo 1 > /sys/class/leds/<led_name>/brightness 
I can see the brightness of the LED change, and henceforth can control the brightness value for any value from 0 to 255.

are the default values for the RGB LEDs set anywhere or overridden, so that they appear to be 0 in /sys/class/leds/<led_name>/brightness, even though they are physically on at bootup?

Warm regards,

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