You can get from distributors new for $4.40 & $5.11 I'm just gonna check if there's any library that supports common-anode
#RGB COMMON CATHODE LED VS COMMON ANODE SOFTWARE#
(rows run from top to bottom and cols run from left to right)Įven if we rotate by 90 degrees the resulting image will be the mirror of the desired one.yep it's gonna take some software fiddling which I'm not willing to do (I love programming but I'm currently working on other projects), I prefer to buy another led matrix. ROW1,2,3,4 = H, H, L, L (the COLS from above)ĬOL1,2,3,4 = L, H, H, H (the ROWS from above)Īnd this will result in lighting leds If we do the swapping the way I suggested, for the common-anode it will be: To be more specific, if we want to switch the two leftmost leds in the upper row, then for the common-cathode it's it's hard to imagine that only I discovered that MAX7219 works with common-anode while everywhere is written specifically "common-cathode" it's hard to imagine the professionals would design it in such an inefficient way And what works for one LED works for any other, so the two matrices are identical.nope! That would work if only one LED is lit at a time, which I'm sure is not the case, without even having to refer to the datasheet, because
In my simple example, everything seemed to be fine. That's a good question, HOW does MAX7219 does the multiplexing? It would be easy to write a sketch to turn on 1 segment at a time, one register at a time, to see where things ended up. If you ran in no-decode mode and defined your fonts you'd be okay, otherwise things could rotated 90 degrees, or maybe flipped somehow, from what you are expecting.
However, if the MAX7219 multiplexes by driving current into one Digit line and sinking current into 1 Segment line at a time, then electrically you would be okay. (EDIT some 4066 bilateral switches could take care of that, although not in the most efficient way perhaps)īack to the main point though, it seems you agree that a MAX7219 will work with common-anode led matrix just as well? I haven't looked in the datasheets if they have such capability, my first though is to switch them on/off alternatively fast enough to get the colors multiplex.but that sounds like a punishment to the chip lolĪ better solution would be to use one MAX7219 and connect the anodes (for common-cathode) or cathodes (for common-anode) of each color maxtrix alternatively to it, by using an arrangement of transistor and logic gates that acts as a SPDT switch. Yep you got a point there, because each color matrix will share either the column or the rows with the other.which in turn are driven by separate MAX7219, so this will need a scheme to multiplex the 7219s. Note that common cathode RGB LEDs and common anode RGB LEDs are not the same! Make sure you get the right one for your project.īuy this Common Cathode RGB LED from Amazon or SparkFun.I think if you have 2 MAX7219 trying to drive a 16x8 matrix (2 color) or 3 driving a 24x8 matrix (RGB) there would be a lot of interference between chips as they each try and drive the anodes or the common cathodes for their own 800 Hz multiplexing. From longest to shortest, the pins are cathode, green, red, blue. Common cathode RGB LEDs have 4 pins – 1 shared cathode (you generally connect this ground) and 3 anode pins for red, green, and blue (you generally connect each of these through a current limiting resistor to an Arduino pin).
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