OUTGOING (commands sent by the controller):
===========================================

There are 3 possible sources for messages sent by the controller

 - Keypad .. a key/button has been pressed or released  (note offset 0x00)
 - GPIO   .. a GPI has changed its state                (note offset 0x20)
 - Analog .. the analog value of an input has changed   (note offset 0x40)


Keypad:
-------

 - the 16 buttons are numbered 0-15 (note 0x00-0x0F)
 - a key press event sends the following command:

     0x90 <key nr + 0x00> 0x7F

 - a key release event sends the following command:

     0x80 <key nr + 0x00> 0x00

 Example:
   Key 14 is pressed and released:

     0x90 0x0D 0x7F
     0x80 0x0D 0x00


GPIO:
-----

 - the 4 inputs are numbered 0-3 (note 0x20-0x23)
 - a low to high transition sends the following command:

     0x90 <input nr + 0x20> 0x7F

 - a high to low transition sends the following command:

     0x80 <input nr + 0x20> 0x00

 Example:
   input 1 goes from low to high and back to low:

     0x90 0x20 0x7F
     0x80 0x20 0x00


Analog:
-------

 - the 8 analog inputs are numbered 0-7 (note 0x40-0x47)
 - by default all inputs are disabled. See below to find out how
   to enable/disable analog inputs
 - on every change of the value of the analog port the following command
   is sent:

     0xB0 <input nr + 0x40> <value>

    (value is between 0x00 and 0x7F -> 0..127)

 Example:
   input 7 changes its value to 42:

    0xB0 0x46 0x2A




INCOMING (commands understood by the controller):
=================================================

There are 3 possible sinks for messages sent to the controller

 - Keypad .. controls the led of a key/button     (note offset 0x00)
 - GPIO   .. sets or unsets a GPO                 (note offset 0x20)
 - Analog .. enables or disables an analog input  (note offset 0x40)


Keypad:
-------

 - the 16 leds are numbered 0-15 (note 0x00-0x0F)
 - all leds can be changed by the special address 0x1F
 - switch a led on:

     0x90 <key nr + 0x00> 0x00

 - toggle a led:

     0x90 <key nr + 0x00> 0x01

 - led blinking:

     0x90 <key nr + 0x00> 0x02..0x1F

    the value controls the blinking speed. Smaller values correspond to
    higher blinking frequencies.

 - switch a led off

     0x80 <key nr + 0x00> 0x00

 Examples:
   Turn led 3 on:

     0x90 0x03 0x7F

   Toggle led 5:

     0x90 0x05 0x01

   led 6 blinking fast:

     0x90 0x06 0x03

   led 14 blinking slow:

     0x90 0x0D 0x40

   turn all leds off:

     0x80 0x1F 0x00


GPIO:
-----

 - the 4 outputs are numbered 0-3 (note 0x20-0x23)
 - all outputs can be controlled by the special address 0x3F
 - for a low to high transition send the following command:
    (this does nothing if the port is already high)

     0x90 <output nr + 0x20> 0x00

 - for a high to low transition send the following command:
   (this does nothing if the port is already low)

     0x80 <output nr + 0x20> 0x00

 - for a state change send the following command:

     0x90 <output nr + 0x20> 0x01

 Example:
   toggle the state of output 3:

     0x90 0x22 0x01

   set all outputs to high:

     0x90 0x3F 0x00


Analog:
-------

 - the 8 analog inputs are numbered 0-7 (note 0x40-0x47)
 - all inputs can be controlled by the special address 0x5F
 - after a reset all inputs are disabled.
 - to enable an input send the following command:

     0x90 <input nr + 0x40> 0x00

 - to disable an input send the following command:

     0x80 <input nr + 0x40> 0x00


 Example:
   enable input 2:

    0x90 0x41 0x00

   disable all inputs:

    0x80 0x5F 0x00