"hacking" color correction system of a professional led screen - Page 1
Forum section: electronics / repair

author: jmibk
author_rank: Regular Contributor
timestamp: July 09, 2019, 07:03:52 pm
content: We have some led screen modules 3,9mm here in our company, that needs some repair. Its a system out of chinese production. Now there are some boards faulty because we tried to repair them and killed the board traces. 4mm leds are f**** small to solder. Now the chinesians need to calibrate the modules, if we order new ones. That is very pricy - so there must be a way to to that myself...https://www.esdled.com/outdoor-dazzle-iii-rental-led-display_p26.htmlShort to the cabinets: a cabinet is a 50x50cm unit, that contains a power supply, two led panels 25x50cm and a receiving card, that converts video data to a kind of multiplexed color format for the two panels. The "standard" is also called HUB75. The receiving card is a Novastar A4s.https://www.novastar.tech/wp-content/uploads/2019/04/Product-Deion-of-the-A4s-Receiving-Card-V1.1.0.pdfNow we need some new panels from the led wall company and they told me that the modules contain some kind of "brain" that contains color correction information. On the panel there is a SPI connection marked with "MISO, MOSI, CS and CLK". Two of them to be exactly - per module.Now I ripped one module apart (because it has fall damage) and figured out, that one module consists out of two separate boards connected via a data adapter board. Now lets speak about the half module 25x25cm....The LEDs are on the back side of the board. It seems to be a multilayer board.A closer look at the board... There is some led driving logic stuff on the board. The chips are LS9929S and LS9739S. If someone can find a datasheet, it would be helpful. But i know from other same systems, that they are a kind of shift registers with current source to drive the anodes and multiplexers to drive the cathodes of the leds.There are also a few chips marked with DF5556, 20 pin package and one 8 pin next to it. The 8 pin is a GD25Q41BTIG (http://www.wasuntech.com/upload/2017-06/21/20140409160111_3496.pdf) that is a 4Mbit flash with SPI like interface. The DF5556 I cant find on the internet, but a little look told me, that it must be a 8bit buffer.Now I will try to read the contents of that chip (and the other one on the second half of the panel. Does someone know a little software (win) to dump the data out of the chip? I think it can be done with an arduino and the serial command to read out the flash and write the data back to the console? Using an ESP8266 should do the job well because the 3,3V voltage of the flash chip?Does someone know how the color correction works and how the data is managed? The data must be read back by the novastar A4s card, because its the only thing that can handle that and there are connections for a SPI memory.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 09, 2019, 10:14:17 pm
content: Have you access to an programmer to see the content in hex edit ??Maybe if you compare 2 -3 eeproms you could see some logic in them ??Thoses p4 tiles are they 64x64 128x128 leds ??Ive played with novastar products, xixun, linsn cards etc ... Some novastar card can adjust the display to get "eveness" among the entire panel, in your pdf you have section 2 overview, surely in the software you could do something ??In older novastar stuff in (dvi display mode) there was a setup section to adjust all the tiles brightness