PWM (Onboard RGB LED)
Controlling PWM on NavQ
The PWM chips are tied to the onboard LED on NavQ. There are three PWM chips: pwmchip0
, pwmchip1
, and pwmchip2
. Each of these "chips" have one PWM line attached to them: pwm0
. To use these PWM lines, you will need to use the sysfs interface.
Using the sysfs interface to control the onboard LED
Step 1
Log into the root
user on NavQ by running this command:
$ sudo su -
<enter password>
Step 2
Navigate to /sys/class/pwm and run the following commands:
$ echo 0 > pwmchip0/export
$ echo 0 > pwmchip1/export
$ echo 0 > pwmchip2/export
Step 3
Now that our PWM lines are exported for each chip, we can change the duty cycle of the PWM lines and enable them. The default frequency is 2730667 Hz. For a 50% duty cycle, we will use half of this number: 1365333. Apply this duty cycle to each chip by running the following commands:
$ echo 1365333 > pwmchip0/pwm0/duty_cycle
$ echo 1365333 > pwmchip1/pwm0/duty_cycle
$ echo 1365333 > pwmchip2/pwm0/duty_cycle
Step 4
We will now enable each line. The colors for each chip are as follows:
pwmchip0
: RED
pwmchip1
: GREEN
pwmchip2
: BLUE
To enable the colors, run the following commands:
$ echo 1 > pwmchip0/pwm0/enable
$ echo 1 > pwmchip1/pwm0/enable
$ echo 1 > pwmchip2/pwm0/enable
Running these commands in succession should enable the LEDs in a RED, GREEN, BLUE pattern until you reach a white LED.
Controlling the onboard LEDs programmatically
Last updated
Was this helpful?