I have a common problem that I can’t seem to solve, my micro’s I/O line are too few, I have looked into serial shift registers but it seems to unclear to me and I get the feeling it over complicates the software for PWM. Is there any way that I can expand my I/O’s with an IC that does not have feedback, and needs a pulse to activate certain channels of that IC.(truth table) Something like a shift register but more simple to use and find.
I am planning on using a BS2 micro, I know its old but for some reason I like it.
Do you need inputs, outputs, or both on the same IC?
A simple option for extra outputs is to use a 3-to-8 or 4-to-16 decoder IC. For 3 or 4 output pins you get 8 or 16 outputs, but only one of these outputs can be active at any instant, so you have to take that into account.
Apart from getting a bigger micro, there are some dedicated I/O expanders around that use I2C, SPI, or another serial comms protocol. They are essentially shift registers at heart, but they’re a little more advanced so you may find them easier to use.
I would honestly suggest you look at the PICAXE line of chips. Their price should be comparable if not better and they come with up to 40 pins total, I believe that is about 32 i/o pins(4 8 bit wide ports).
