Author Topic: 16x8 LED matrix based on TLC5920 - issues  (Read 517 times)

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Offline FlyingDutch

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16x8 LED matrix based on TLC5920 - issues
« on: October 17, 2021, 11:18:49 am »
Hello,

i am attempting to make 16 rows X 8 column LED driver based on "Texas Instruments" IC - TLC5920. Here is product page on TI website;

https://www.ti.com/product/TLC5920

and here data sheet:

https://www.ti.com/lit/ds/symlink/tlc5920.pdf?ts=1634467956053&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTLC5920

I am using custom board with STM32F103VGT6 MCU and lightly modified C language code from "Matrix Clock" project from this link:

http://www.carbonfrog.com/Products/MC201V1.html

When i try display on LED matrix constant pattern (not changing pattern) everything is OK. When I am trying to display pattern which is changing wit frequency about 20 Hertz I had some issues - relay  on that slightly shine columns that shouldn't shine.

I am using semaphores to synchronize displaying data on LED driver and refreshing display procedure. Can someone has experience with this TLC5920 IC?
I am also wondering if it is good idea to make TLC5920 IC controler based on small FPGA and writing VHDL code?

Thanks in advance and Regards
 

Offline TomS_

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Re: 16x8 LED matrix based on TLC5920 - issues
« Reply #1 on: October 19, 2021, 08:21:16 pm »
How are you driving the LATCH pin?

At a guess you are idling high. When this pin is high, the latch is transparent, which means you are probably seeing the data as it is being shifted through.

You will want to keep LATCH low when shifting, then give just a brief high pulse to allow the newly shifted data through to the output drivers.

FPGA .. depends on the size of the matrix you want to drive, and how fast you want to refresh it. Small matrices can be done easily enough in software with timers and interrupts.
« Last Edit: October 19, 2021, 08:31:06 pm by TomS_ »
 
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Offline FlyingDutch

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Re: 16x8 LED matrix based on TLC5920 - issues
« Reply #2 on: October 22, 2021, 12:21:57 pm »
Hello,

today I had a little of time that I could spend on this subject. Simple VHDL code had been written by me to generate signals needed to drive serial in to TLC5920 IC. Here is link on polish forum Forbot.pl - translated to English by "Google Translate" wher I described further works on this subject:

https://forbot-pl.translate.goog/forum/topic/20667-tlc5920-sterownik-matrycy-led-16wierszy-x-8-kolumn/?tab=comments&_x_tr_sl=pl&_x_tr_tl=en&_x_tr_hl=pl&_x_tr_pto=nui#comment-169760

Best Regards
 


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