Bench test for DOT Matrix
DMD tester
For plasma display
128 x 32
and
192 x 64
Presentation
Mounting is done directly on a plate of experimentation, it integrated the control (CPU, memory) as well as part power supplies high voltages. All is fixed in an insulating plastic enclosure to avoid any risk of electric shock.
The LEDs indicate the presence of different voltages (+ 5v, + 12v, + 62v, - 100v and - 110v) and the good functioning of the CPU.
Control is entrusted to a PIC 18F252 microcontroller that is associated with an EEPROM 24C512 memory. In this version, only 128 x 32 displays are taken into account.
The display can be modulated to 4 levels of intensity (per pixel) and allows the use of images previously stored in the EEPROM. Some samples:
Evolution
In order to also test the large displays DMD 192 x 64, we have developed an improved version. It uses a more powerful processor PIC 18F2620, while maintaining exactly the same hardware. Its characteristics are identical, we have just added a button to select the mode mode 128 x 32 or the mode 192 x 64.
As you can see on these photos, this DMD 192 x 64 is largely degassed and some lines are missing.
Thanks to "Nurbo" we have graciously loaned this display for our tests.
Compatibility
We had the opportunity to check the compatibility of our tester with LED DMD modules, and as you can see, it works perfectly.
Toolbox: encoder
In order to generate the images used in this assembly, we developed a specific tool. This one makes it possible to convert an PNG image 128 X 32 (or 640 x 160 from WPCEdit capture) into a binary file of 1024 bytes, which will be then easily integrable in a EEPROM (24C512 for example).
The binary result includes two planes (DIM and MEDIUM) of 512 bytes each (128 x 32 bit), intended to control the brightness of the display (with a typical scale of 0%, 75%, 90% and 100%). The detection of brightness levels used in the original PNG (RGB 24 bits) file, is totally automatic and not need any adjustment.
This tool also works for large displays, with a PNG 192 x 64 (or 960 x 320) image. The binary file generated is 3072 bytes and includes two plans (DIM and MEDIUM) of 1536 bytes each (192 x 64 bits).
Samples of useable PNG (128 x 32) pictures:
It is also possible to use 5X zommed PNG pictures (640 x 160), coming from a screen capture of WPCEdit
(the picture mode may be set to black & white, but colored pictures works also):
Toolbox: decoder
This tool performs the reverse operation of the previous, it generates an image in PNG format 640 x 160 (or 128 x 32) from a binary file. This one must have a size of 1024 bytes, or 2 plans of 512 bytes (DIM and MED).
For large displays, the file must be 3072 bytes, or 2 plans of 1536 bytes (DIM and MED). The generated PNG image will be 960 x 320 (or 192 x 64).
Distribution
This achievement is currently unavailable, but we are studying the possibility of its dissemination (free or paid) for the future.
