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| Connecting 8x8 matrices to a 12x16 driver |
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| danners430:
Hey folks, I've got 3 8x8 LED dot matrix displays which I need to drive. The obvious way is to use the MAX7219 driver for each of them, but seeing as I have a total of 52 matrices, that gets very expensive, very quickly... The solution I stumbled upon is the IS31FL3733, which seems ideal. It's a 12x16 driver, so a total of 192 nodes, which of course is the same as my 3 matrices. The problem I've come across is how to connect them up - I can easily connect matrix 1 & 2 to columns 1-8 & 9-16 respectively, but that leaves matrix 3 spanned across all 16 columns, and it of course only has 8 inputs... :-// I attach a photo below of the dilemma... The only solution I've been able to think of, and I'm not sure if it would work, is to connect CS1 to CS9, CS2 to CS10 etc. at matrix 3, using diodes to prevent "backflow" into the other matrices... would this work? Cheers for the help guys |
| Rolo:
Did you look at the Holtek HT16K33? This is I2C and can drive up to 8x16 leds in a matrix. Cheaper as the MAX7219. Adafruit uses it in their Led backpacks is various configurations. |
| danners430:
--- Quote from: Rolo on February 05, 2019, 05:55:57 am ---Did you look at the Holtek HT16K33? This is I2C and can drive up to 8x16 leds in a matrix. Cheaper as the MAX7219. Adafruit uses it in their Led backpacks is various configurations. --- End quote --- Hmm, they would work just fine too... Only downside is I'd need two chips for each board (3 matrices per board), so a little more expense and programming overhead - by no means unachievable, and certainly a good backup plan if the IS31FL3733 doesn't work out :-) Sent from my ONEPLUS A3003 using Tapatalk |
| rs20:
If you wanted to drive 6 8x8 displays with 2 IS31FL3733s, then you'd be fine! (Sort of... maybe not even actually) It's very clever to stagger the two 8x8 displays the way you did to increase your chances, but unfortunately your suggestion doesn't work, at least, not naively. If you used a diode to steer CS10 into CS2, then trying to turn on LED K2 via the diode would also turn on LED K10 in the green array. In fact, the drop across the steering diode would probably mean that only K10 would turn on, K2 would be off or very dim. I haven't prepared a formal proof, but I have a vague hunch that it's impossible to drive 3 8x8 displays with the IS31FL3733s, unless you somehow electrically split one of the displays in 2 (or redefine the requirements in such away that the artifacts from the weird wiring work in your advantage.) |
| danners430:
--- Quote from: rs20 on February 05, 2019, 06:14:20 am ---If you wanted to drive 6 8x8 displays with 2 IS31FL3733s, then you'd be fine! (Sort of... maybe not even actually) It's very clever to stagger the two 8x8 displays the way you did to increase your chances, but unfortunately your suggestion doesn't work, at least, not naively. If you used a diode to steer CS10 into CS2, then trying to turn on LED K2 via the diode would also turn on LED K10 in the green array. In fact, the drop across the steering diode would probably mean that only K10 would turn on, K2 would be off or very dim. I haven't prepared a formal proof, but I have a vague hunch that it's impossible to drive 3 8x8 displays with the IS31FL3733s, unless you somehow electrically split one of the displays in 2 (or redefine the requirements in such away that the artifacts from the weird wiring work in your advantage.) --- End quote --- Dangit... I was determined to get it working :-( It may be that I find some strange way to get it working in the next couple days, but I'll put it on the back burner for now --- Quote from: danners430 on February 05, 2019, 06:07:43 am --- --- Quote from: Rolo on February 05, 2019, 05:55:57 am ---Did you look at the Holtek HT16K33? This is I2C and can drive up to 8x16 leds in a matrix. Cheaper as the MAX7219. Adafruit uses it in their Led backpacks is various configurations. --- End quote --- Hmm, they would work just fine too... Only downside is I'd need two chips for each board (3 matrices per board), so a little more expense and programming overhead - by no means unachievable, and certainly a good backup plan if the IS31FL3733 doesn't work out :-) Sent from my ONEPLUS A3003 using Tapatalk --- End quote --- Well, searching for the HT16K33 did have one advantage - it led me to the HT1632C, which can drive 24x16 LEDs - which is literally double what I need, since one of my boards is a "measly" 24x8... Means I could theoretically connect two boards together, with a master and slave board, with a simple 32 way connector between the two :-) |
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