View source for Equipment/Piccadilly circus LED sign

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The LED sign is awesome in every way the jumbotron was not: it has high pixel density, brightness, and low weight, AND pretty simple insides.

This Howto is a basic hack to drive on of the tiles

== What is what ==

The board is made of segments each with four columns and a column has three tiles. Each tile has 16x16 pixels RGB.

In this document we are interested in the tiles as they are the easiest. They can be driven my AVR/Arduinos

Instructional [http://www.youtube.com/watch?v=6iHTbGsnI8Q video] by Mike Harrison

[https://groups.google.com/d/topic/london-hack-space/Ns7keUUNI1M/discussion Documentation]

== Pinout ==

The tiles have the following pinout

  1. FLACK
  2. NC
  3. NC
  4. MA0
  5. MA1
  6. NC
  7. BRIGHTNESS
  8. NC
  9. R_EN
 10. G_EN
 11. B_EN
 12. GND
 13. R_DATA
 14. GND
 15. G_DATA
 16. GND
 17. B_DATA
 18. GND
 19. SCLK
 20. GND

Inside the module looks like this

[[File:TB2706-sipo.png]]

Note: The arrangement of the pixels is not a nice linear buffer! 


  Top left front pixel
  \/
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |0f|0e|0d|0c|0b|0a|09|08|07|06|05|04|03|02|01|00|  |1f|1e|1d|1c|1b|1a|19|18|17|16|15|14|13|12|11|10|
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |00|01|02|03|04|05|06|07|08|09|0a|0b|0c|0d|0e|0f|  |10|11|12|13|14|15|16|17|18|19|1a|1b|1c|1d|1e|1f|
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |                                                                                                  |
 |                                            .  .  .  .                                            |
 |                                                                                                  |
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |cf|ce|cd|cc|cb|ca|c9|c8|c7|c6|c5|c4|c3|c2|c1|c0|  |ef|ee|ed|ec|eb|ea|e9|e8|e7|e6|e5|e4|e3|e2|e1|e0|
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |d0|d1|d2|d3|d4|d5|d6|d7|d8|d9|da|db|dc|dd|de|df|  |f0|f1|f2|f3|f4|f5|f6|f7|f8|f9|fa|fb|fc|fd|fe|ff|
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
                                                                                                  /\
                                                                             Bottom right front pixel

== Writing stuff! ==

Hook all the pins up and strobe them all high. Basically the FLATCH signals the start of the frame. The R_EN, G_EN, B_EN need to be pulsed high at the start if you want those colours. 


Then drop them all low. Now write one bit by placing the data on R_DATA, B_DATA and G_DATA pins with CLOCK high. Then drop the CLOCK. Data is written on the falling edge.

== How should it work? ==

Well this is a hack. Please read the documentation for proper timing diagrams. It is supposed to be driven at 12.5mhz but anything lower shouldn't spook it too much and an ardiuno/avr is not going to get close to that clock frequency.

RGB gradients are accomplished by writing the data fast enough to do PWM.

== Things done with the tile so far ==
* The [http://www.icrobotics.co.uk/wiki/Main_Page Imperial College Robotics Society] has made a lot of progress, and their [http://www.icrobotics.co.uk/wiki/index.php/Large_LED_Screen code] now displays various parametric visualizations, as well as gifs, with good colour mixing.

=== The H ===
[[File:Led-h.jpg]]

[[Category:Projects]]