LedBorg arrives: time for some pretty GPIO-driven colours

Yeay! I bought a LedBorg recently from PiBorg (only cost a few quid) and it has proven very straightforward to set up and use. LedBorg is essentially 3 LEDs on a very small (as in VERY _small_) expansion board for the Raspberry Pi. It is about the width, and half the length of my index finger making it possibly the teeniest hardware add-on I have every installed.

LedBorg’s LEDs can be set to off, low or high for each of the red, green and blue diodes. In combination this can be used to generate up to 26 colours. The setup instructions are clear and easy to follow. Just make sure that if you have a 512MB Raspberry Pi that you follow the Rev 2 instructions that are on the page.

Changing the colour is as easy as issuing the following from the terminal:
echo “RGB” > /dev/ledborg
replacing RGB with the off (0), low (1) or high (2) value for each of the red, green and blue diodes.

A few examples:

echo “222” > /dev/ledborg
(all LEDs at maximum output)

echo “000” > /dev/ledborg
(all LEDs are off - strictly speaking the LedBorg is not actually outputting black... it is off)

echo “200” > /dev/ledborg

Darker Red
echo “100” > /dev/ledborg
(appears less intense than full Red’s 200)

echo “220” > /dev/ledborg

echo “202” > /dev/ledborg

Ok, so what practical uses can it be put to? Anything from a random colour generator, to colour waves to a CPU usage monitor. In the latter case the demo application that can be installed from PiBorg will change LedBorg’s colour output from Green to Red when the CPU spikes. Here’s an example of a random colour generator that I wrote quickly in Python:

import random, time

while True:
    lbRed = random.randrange(0,3)
    lbGreen = random.randrange(0,3)
    lbBlue = random.randrange(0,3)

    lbColour = str(lbRed)+str(lbGreen)+str(lbBlue)

    LedBorg = open('/dev/ledborg', 'w')
    del LedBorg

    print lbColour

This will pick a random value between 0 and 2 for each of the 3 diodes, set these values, causing the LedBorg to light up accordingly and then print the colour values selected to the terminal. Note that the range is specified as 0,3 as, from tutorialspoint the second value is the stop value and is excluded from the range. Try changing this to 0,2 and you will see that when run the program never output the number 2 (ie: high, LED on maximum) to the terminal. The Python docs do not explain this subtlety.

I have various plans for LedBorg using web.py, AJAX and my Android phone for remote control of my Pi when not connected via SSH and with no monitor plugged in. I can see LedBorg as a very handy gadget to give visual feedback that whatever I set on my Android phone has been so set on the Pi.

PiBorg also make the PiBorg (unsurprisingly), an interesting robot controller for the Raspberry Pi. Here’s a thought: if you cross a LedBorg with a PiBorg do you get a Cylon?

The MagPi issue 7 is out

The MagPi issue 7 has been released. What’s more I have two articles published in this issue: an interview with Mike Thompson who created Raspbian, and my first ever published computer program! I took over The Python Pit this month to demonstrate how one can implement command line arguments to make configuring an application that is about to be run easier than having to manually edit the program code.

I am especially pleased with the program I wrote as it generates graphical output (see image below) that I used to draw by hand when I was a child. Back then I don’t even think it occurred to me to write a program to do this!


The program supports a number of command line arguments to change the output. Run:
line_generator.py -h
to see all of the options.

For your viewing pleasure, here’s the output of the above:

usage: line_generator_edit.py [-h] [-s SCALE] [-t STEP] [-r {y,n}]

Render shape

optional arguments:
-h, --help show this help message and exit
-s SCALE Render size, default=2, 200x200px)
-t STEP Step value (default=5): lower the value for denser lines
-r {y,n} Render line by line (slower) (y) or only display finished object
(faster) (n)? (default=y)