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Author Topic: max7219cng problem all my 8x8 leds are on and i can't turn them off  (Read 1117 times)
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hi all
i have a problem with working with the max7219cng
i am reading the beginning arduino book and i did exactly like the books says but my dot matrix led 8x8 is on all the time

i got my max7219cng from ebay (i got 2 max7219cng) and i think its fake or maybe damaged but it's possible that i don't know how to work with the max7219cng
i am quite new to electronics and arduino but i managed to get my dot matrix led 8x8 work with the 74hc595 chip even with 2 74hc595 and it works fine.

the problem is that i connect everything good (i even check with multiple sites ) but all the 64 leds are all the time on i even tried different resistor with no help i only get 2 modes everything is on or everything is off

iv'e added the code and the sketch

can anyone run this code and connect his max7219cng to dot matrix 8x8 and see if it's working
does anyone know what is my problem ?

i tried to test the max7219cng  with wiring only 2 regular leds and see if i am able to control only 2 leds and i was unsuccessful(no matter what i did both of them were power on

i am pretty frustrated and need your help

thank you very very much  smiley


* max7219.JPG (92.25 KB, 815x549 - viewed 49 times.)
* _021_LED_Dot_Matrix_Display_Scrolling_Message.ino (12.71 KB - downloaded 20 times.)
« Last Edit: February 02, 2013, 09:54:26 am by ygarti » Logged

Norfolk UK
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A quick look at the drawing and the power, data & IREF look to be connected fine. I cannot check the 8x8 matrix connections as you have no pinout description for it. Is the matrix common cathode or common anode, the MAX7219 need common cathode.
As to the code, I would suggest you download the LedControl library here http://playground.arduino.cc/Main/LedControl and check your wiring with the example programs it includes. It's tried and tested so you should be able to isolate if the problem is code/wiring quickly.
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hey man, I think i have the exact same problem as you: http://arduino.cc/forum/index.php/topic,146483.0.html

I bought 5 MAX7219s, all from digikey, and none of them are working like i want them to. I have no idea how to fix it. Hope we can figure out something soon!
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30 Jahre Elektronikbastelei, Programmieren null Ahnung!
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Hi, in german group one guy did have the same problem. He found, that he bought a lot of fake "chips"
There is a photo with true 7219 and bad copy. And he did post his source!
http://arduino.cc/forum/index.php/topic,138061.15.html
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Well, just finished a small project using Max7219 -- a new buffer based led matrix library that is fast enough for games. During development, I encountered the same problem, but it turned out that I was not sending commands correctly -- I was not lowering and raising the LOAD/CS line for each command/data. So the MAX7219 was in some weird state that wouldn't shutdown, even starting from beginning.

To fix it, turn off the power and send in the correct sequence of command via SPI, now everything works fine.

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