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Arduino led matrix max721911/20/2023 ![]() The one Arduino output pin, and each buffer output can drive 8 of the MAX7219 chips.Ĭ. I can drive several (2 to 4) buffers with The Arduino output pin and the 8 MAX7219 inputs. ![]() Many displays I initially experiment with, put a non-inverting buffer pair in series to between The outputs of these 4 (One each to a set of 8 Max7219 chip displays). ![]() Take my Arduino output pin for CS, and run that into 4 of my non-inverting buffers, connecting Take a pair of inverting 7404 gates, and cascade a pair so they are non-inverting.ī. It looks like Data-In and Data-Out cascade "through" each max7219 chip, so I don't need to doįinally, to confirm my understanding If I want to drive 4 sets of modules, then I can experiment withĪ. Second, for using these buffers, I assume we are only talking about the CS and CLK lines, right? Is there any harm in experimenting with the regular 7404 chips, or is there a large I don't have any 74HC04's, but I have a parts draw full of regular 7404 chips. Lines to verify what is going on speed wise, and how clean the signal looks.Ĭan't hurt to experiment, so when I get time this week, I will try some 7407 buffers. That is 10hz ? I should hook my scope up to the CLK and CS To the other poster that mentions it is a signal delay issue on the long lines, can that be trueĪt these speeds? We are updating the display (according to the code in the library examples), In other words, is it still the case where I need buffer chips?] [Or, for fan-out, is the line length and capacitance of the inputs more important than the 1 uA load? Now, you said the UNO output pin can drive 20 mA, and the MAX7219 inputs only take 1 uA.īut then, where did you get the mention above for driving only 6 of the MAX7219 chips? With 5 of the 4-in-1 modules strung together, that means the UNO output pin for CLK is driving 20 of the MAX7219 chip inputs Each module has four 8x8 LED matrix unit, with 4 of the MAX7219 chips. You mention that, according to the chip specs, an UNO output pin will safely drive 6 of the LED MAX 7219 chip inputs. ![]() Ideas? Has anyone built a large diplay with lots of these modules? It really feels more like TTL signal instability due to how many chips are sitting on the CS and Or could it be software timing in the example programs with the library? This requires something like a 7407 buffer IC between each module set of 4? These lines, at least CS and CLK, look like they feed all matrix modules in parallel. That are doing the serial clocking? These modules use 3 output pins for CS, CLK, and Data In. I suspect or get a feeling that maybe there is too much load for the 3 output pins on the Arduino I did add bypass and filter caps to each of the modules. I am using an external power supply for the LED matrix displays, not from the arduino uno. It works for scrolling text, but with random corruption of certain LEDs in some of the blocks. I set in the library max modules = 24 and compile/upload. QUESTION: If I create a daisy chain of four of the 4-in-1 modules (16 of the 8x8 matrix displays)Īnd set max modules = 16 in the library, everything works fine for scrolling text and bit-mapped graphics.īut if I add a fifth or sixth module, I get random corruption in various 8x8 blocks of the display.įor example, if I string 6 of these 4-in-1 displays, that equals 24 of the 8x8 matrix squares in a row. I tested each module using the MD_MAX72xx library example programs. These are 4 of the 8x8 LED matrix displays on a single board, each 8x8 matrix having a MAX7219 chip under it. I purchased a number of the MAX7219 LED Matrix 4 in 1 modules (8x32).
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