C program for controlling BlinkM leds from an embedded Linux system
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A command line program for controlling BlinkM leds connected to the I2C bus of a embedded Linux machine. Typically only embedded Linux systems export /dev/i2c busses to userland.

The default assumes a Gumstix Overo board.

If you are using an RPi, then change the /dev/i2c-X constant in i2c_functions.c to use the appropriate i2c bus for your board.


There is a make file for building the project.

    $ git pull git://github.com/scottellis/overo-blinkm.git
    $ cd overo-blinkm
    $ <optional> edit i2c_functions.c
    $ make


RPi kernels might not load the i2c drivers automatically. If you are running the Debian Wheezy image, you can add the following two lines to /etc/modules


Gumstix kernels load the i2c drivers by default.

You will need to change permissions for /dev/i2c-N device if you are running blinkm as someone other then root.

A one-time fix is to run the following as root (Gumstix example)

    chmod 0666 /dev/i2c-3

This will get overwritten on your next boot though.

A more permanent fix is to create a udev rule file like this


With the following single line

    KERNEL=="i2c-[0-3]", MODE="0666"

Run the blinkm program without arguments to get the available commands.

    $ ./blinkm

    Usage: blinkm <command> <args>

    The led address is optional and defaults to 0x09.
    Use a comma separated list to address multiple devices in one command.
    The color arguments are optional and default to zero.

    Available Commands
            set-rgb [-d led] [-r red] [-g green] [-b blue]
            get-rgb [-d led]
            fade-rgb [-d led] [-r red] [-g green] [-b blue]
            fade-hsb [-d led] [-h hue] [-s saturation] [-b brightness]
            fade-random-rgb [-d led] [-r red] [-g green] [-b blue]
            fade-random-hsb [-d led] [-h hue] [-s saturation] [-b brightness]
            play-script [-d led] -s <script id or name> -n num_repeats
            stop-script [-d led]
            set-fade-speed [-d led] -f speed
            set-time-adjust [-d led] -t adjust
            read-script [-d led]
            write-script-line [-d led] -n line_no -t ticks -c cmd -a arg1[,arg2[,arg3]]
            set-script-length-and-repeats [-d led] -l length -n repeats
            set-address -d new_led_address

The first command you probably want to run is find-leds.

    $ ./blinkm find-leds

    Scanning I2C bus for BlinkM devices...
    Found a BlinkM at address 1 (0x01)
    Found a BlinkM at address 2 (0x02)
    Found a BlinkM at address 3 (0x03)
    Found a BlinkM at address 4 (0x04)
    Found 4 devices


  1. Write script function hasn't been tested much.

  2. Need to recover the bus after the command to change an led address. Right now you need to power cycle the led which is okay, but you also need to power cycle the overo or the i2c bus stays hung.

  3. GetAddress is not implemented. Investigate if i2c broadcasts are possible with the overos.

  4. Add code to read in scripts from a file.