So I'm making a 16 x 6 LED matrix and I'm having a couple issues with the registers. When I originally built the matrix I planned to use a current sink driver so I made it correspondingly. Now I'm using regular registers so its reversed. To deal with this I just switched things around in the code. What I mean is instead of writing B00000000 and B00000000 to turn everything off I use B11111111 and B11111111. For testing purposes I'm just using the first row of LEDs so I'm not getting into the more tricky coding of multiplexing with registers. So far there are 3 problems.
First of all I'm having power problems, what I mean by that is that when I have a few LEDs on they are all pretty bright but the more I turn on the dimmer it is. I'm not sure how to get around this other than using 16 small transistors (one for each column) but that seems a bit much. Luckily I started off on a breadboard so its still pretty easy to change things.
Second when I turn on all of the LED's (write B00000000 and B00000000) none turn on, but if I turn all but 1 on it works (write B00000000 and B00000001) my only idea on this one is that its some sort of feature of the registers as in when all of the LEDs are supposed to be off it automatically just goes to high impedance or something which is a problem for my setup. If that is the problem then maybe using transistors for each column would be good because I could run it as a flip flop so that the code would be normal again.
Thirdly the 8th output pin on my first register doesn't seem to work like it should. I think this might be the ic itself or just some problem with the temporary circuit I made but I don't see a problem. Its weird though because its not like it never works because it sort of flashes really fast every time it gets rewritten to. To my surprise when i was just messing with the code and wrote a program that just went through each LED one at a time and ran it so that it only turned on each one for 1 ms (making a multiplexing type always on effect) it was just as bright as all of the others. Thats what leads me to suspect the actual IC but I don't know.
Any input would be helpful! Thanks in advance