I'm making a clock and part of it is a big **** screen of 8x40 leds. But I'm having trouble driving it. You need a loooot of output pins to drive that kind of screen.
I assembled a driver for the screen myself. I daisychained six 74hc595 chips to drive the 40 columns and to sink the current of the 8 rows (through transistors). You can see the schematic here.
Here is the datesheet of 74hc595
But writing the code, I got in a bit of a pickle. I can't seem to get a non-flickering image. And even worse, if I use a lot of 'heavy' characters that light a lot of leds, the image gets worse and more flickery. Here's the code I'm using.
Any ideas? 'cause this is kind of exceeding my capacities.