Learning Embedded Linux with Beagleboneblack — Part1

Photo by Gabriel Heinzer on Unsplash

This is a beginner-friendly effort to understand Embedded Linux in a straightforward manner. Previously, I tried learning through device drivers (mostly theoretical), but it proved challenging because there were no hands-on exercises. Now, I’m using a BeagleBone Black, enabling the creation of practical projects while learning each Embedded Linux concept.

Let’s start with a basic program, the classic first project: Blink an LED!

Blink an led

The BBB has four user-controllable LEDs (USR0 through USR3). We can control these directly from the terminal.

steps

1. Connect BBB using the USB mini cable to the computer
2. Open any SSH terminal (Putty, MobaXterm) and login to BBB (default username: debian, password: temppwd)
3. Check virtual directories for LEDs in your BBB
   ls /sys/class/leds

4. So we have 4 leds present on our BBB which are represented by usr0, usr1, usr2 and usr3. We can see parameters to control the LEDs inside each of the led directory.
ls /sys/class/leds/beaglebone\:green\:usr0

5. We’ll be using brightness parameter to blink the each of the LED individually. Following commands will turn on the LED first by writing 1 to brightness. Second command will turn off the LED.
echo 1 > /sys/class/leds/beaglebone\:green\:usr0/brightness
echo 0 > /sys/class/leds/beaglebone\:green\:usr0/brightness

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6. We can write a script to sequentially turn on all the LEDs

#!/bin/bash
# A simple loop to blink USR3 10 times
for i in {1..10}
do
    echo 1 > /sys/class/leds/beaglebone:green:usr0/brightness
    echo 1 > /sys/class/leds/beaglebone:green:usr1/brightness
    echo 1 > /sys/class/leds/beaglebone:green:usr2/brightness
    echo 1 > /sys/class/leds/beaglebone:green:usr3/brightness
    sleep 0.5
    echo 0 > /sys/class/leds/beaglebone:green:usr0/brightness
    echo 0 > /sys/class/leds/beaglebone:green:usr1/brightness
    echo 0 > /sys/class/leds/beaglebone:green:usr2/brightness
    echo 0 > /sys/class/leds/beaglebone:green:usr3/brightness
    sleep 0.5
done

Conclusion

Each of the LEDs are controlled by files in the Linux environment. This is the fundamental concept of learning Embedded Linux. Everything is controlled through a set of files! That’s it! We’ll continue this journey in the next part.