Lighting

PWM Control

The pwm-ctrl utility is a command-line tool that facilitates the control of pulse-width modulation (PWM) on specific GPIO pins. PWM is commonly used for adjusting the brightness of LEDs.

Usage

The command syntax for the pwm-ctrl utility is as follows:

root@ing-teacup-2a10 # /sbin/pwm-ctrl [-l] <gpio> <brightness 0-100>

Where:

• -l: Lists all available PWM-capable GPIOs on the system.
• <gpio>: Specifies the GPIO number for PWM control.
• <brightness 0-100>: Sets the brightness level from 0 (off) to 100 (maximum brightness).

Listing PWM Capable GPIOs

To find out which GPIO pins are capable of PWM, you can use the -l option. This will display a list of all the PWM-capable GPIOs along with their corresponding labels and pin numbers:

root@ing-teacup-2a10 # pwm-ctrl -l
Available PWM-capable GPIOs:
GPIO 46 = PWM0 (PA14)
GPIO 54 = PWM1 (PA22)
GPIO 49 = PWM0 (PB17)
GPIO 50 = PWM1 (PB18)
GPIO 59 = PWM2 (PB27)
GPIO 60 = PWM3 (PB28)

GPIO Compatibility

It is important to note that PWM control can only be applied to GPIOs that support PWM functionality. Attempting to use the pwm-ctrl command on non-PWM-capable GPIOs will not work, as these pins do not support the function necessary for varying power outputs.

Controlling Brightness

Once you have identified the correct GPIO pin from the list, you can control the brightness by specifying the GPIO number and the desired brightness level. For example, to set the brightness of GPIO 46 to 50%:

root@ing-teacup-2a10 # pwm-ctrl 46 50