Current place and operation
On the top of the burnstation, power is supplied by an old AT unit
Project goalsendre has bought a LED display made by Mediotext a while ago from Vatera, with dried out capacitors. The project aims to replace the original microcontroller with Arduino and to develop an Arduino library so that one can make use of the display for various projects.
The displayThe display itself is built up with 96x7 5mm red LED pixels made by german firm Mediotext, and has had a 6502 microcontroller that has been replaced with Arduino lately. Award goes to MrT for his excellent reverse engineering work.
InterfaceThe display is equipped with a DB-9 connector on the top, having the folling pinout:
OperationThe X and Y axis "addressing" are completely independent and driving them has completely different approach.
- X axis: a LED is "addressable" by filling the shift registers with loading all of the 96 LEDs levels (Arduino
shiftOut()function) corresponding to a specific row.
- Y axis: a row can be selected by pulling the ROW_ID_x levels down. Obviously only one row can be selected at a time.
- Blanking: The display can be blanked (for example during the shiftOut update period) with all the lines pulled down.
Arduino codeArduino source code is available in the https://github.com/hsbp/arduino2mediotext repository. The master branch has code that scrolls a hardcoded text.
Remote control branchThe remote-control branch makes the Arduino a dumb framebuffer that can be controlled over a serial connection. Currently, the protocol offers only one command, block update and a speed of 19.200 bps.
Block update commandThe block update command deals with 8-pixel horizontal blocks, resulting in 12 × 7 such blocks. The header bits look like the following:
- AAA is the first row to be updated (0-6)
- BBB is the first row not to be updated (1-7)
- CCCC is the first 8-pixel horizontal block to be updated (0-11)
- DDDD is the first 8-pixel horizontal block not to be updated (1-12)
Python APITo make things easier, a simple Python API is implemented by the Remote class, having the following methods. Pixels are expressed with tuples having two members, X and Y.
- __init__ (serial_class=Serial) the only optional parameter can be used for testing, otherwise the
/dev/ttyUSB0(first USB-Serial converter on Linux) will be used using pySerial
- set_pixel(pixel, value) sets the pixel specified by the first parameter to value (True means lit, False means dark)
- get_pixel(pixel) returns the current state of the pixel specified by the only parameter
- flush_pixels() if any pixels has changed since the last flush, it updates the affected region
Note: for performance reason, set_pixel calls doesn't take effect until the next call to flush_pixels, but get_pixel already returns the new value
If you need low-level access, the
framebufattribute stores the framebuffer as a flat list of boolean values, from left to right then top to bottom. Reading it should not cause any problems, but writing it is discouraged as the next call to flush_pixels will not know which pixels you changed.
- test cases, providing a 100% code coverage of the Python Remote class
- spectrum visualization using pyaudio and numpy (YouTube video)
- hackerspace uptime using HackSense data (YouTube video)
- temperature display of zoldfal using SpaceAPI data
- game of life, displaying Conway's classic on a sphere (top-bottom and left-right edge pixels are neighbours)
- scroller, capable of displaying any monochrome PNG, example:
As seen on..
Contributors to this page: eapo
Page last modified on Thursday 29 of May, 2014 11:18:25 CEST by .