![]() So all you need to do to get the wiring right is make sure the cathodes in your matrix are connected to the DIGit pins on the chip, and your anodes are connected to the SEGment pins on the chip. The max7219 can drive either type of 8x8 matrix because, as I said, all matrices are common cathode. Those have 8 pins for each of the individual leds in the segments, and one common pin for the common cathodes of each digit. It can only be used with common cathode 7-seg displays. Max7219 was originally designed to drive up to 8 digits of 7-segment led display. The data sheet describes both types, so what is printed on the matrix itself? The convention is that the two rows of pins on the back are horizontal rows. Even then, with a square matrix, who is to say which way up it should be held? Turn it 90° and rows become columns. The two different possible configurations are common cathodes on each row and common anodes on each column, or vice versa. Well, the term "common cathode" is useless when describing led matrices. pdf for the matrix says it is Row Cathode which I'm guessing is common cathode. ![]() I know there are rows and columns and I can see what wires go to the MAX7219 but to the matrix I am confused. I only put a few wires in and I tried to copy the wires from another video showing one wired up. I can't count how many time I have pulled all the jumpers and tried it all again. I guess I can't seem to read the 8x8 schmatic or I am just doing it all wrong. I am using an uno v3 and the matrix is from adafruit. and this to show the hookups from the chip to the matrix****. ![]() I am using this reference for the MAX7219. If not – switch them and try again.I getting to my wits end. If the diode lights up then you’ve successfully matched the positive probe with the anode and the negative probe with the cathode. Just turn the multimeter to its diode setting (it should be identified with a diode-shaped symbol) and touch each probe of the multimeter to the diode’s terminals. If you’re still uncertain you can just use a multimeter to test which end of the diode is its anode and which – its cathode.The pin near the flat edge should be the cathode. If the pins have been trimmed and equal in length, look at the edges on the diode’s outer casing – one should be flat and in line with the diode and the other should be extending a bit.In LEDs, the LED anode-cathode differentiation is done via the length of each pin at the end of each diode – the longer pin is usually the anode and the shorter pin – the cathode. ![]()
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