595 shift register (SIPO)

Forum 2005-2010 (read only) Hardware Interfacing
1

Hey all,

As always thanks for taking the time to read this. I was just curious, I have a bunch of spare 595 shift registers I was using with my binary clock project laying around.

Put simply, what is the Q7" (pin 9, serial out) pin used for on the 595 shift register (as illustrated on the diagram here: http://www.arduino.cc/en/Tutorial/ShiftOut).

I was gonna start playing with COM interfacing and basically run this the other way around. Instead of outputting to LED's from arduino I wanted to put switches there and shift into to arduino. Can I use the 595 chip for this or do I need to use a 4021?

Obviously, it's parallel out, so I'm guessing no, but I noticed there is that serial interface on pin 9. Upon plugging pin 9 in as the ShiftIn tutorial suggested for the 4021 (http://www.arduino.cc/en/Tutorial/ShiftIn) it does not read the inputs with the 595.

Every now and then if i hit a certain button it gives 8 1's, but that's been the only response I got and I'm assuming those 1's were probably from it catching serial information on the latch pin or something to that effect.

I'm happy to order some 4021's as they are extremely inexpensive, I just wanted to make sure I needed to before doing so.

Thanks,

Y-aji

2

you need a 597 if you want to input data with shift registers. q7 is used to daisy chain more shift registers together to get more outputs with the same inputs.

3

ohhhh.. cool.. Thanks so much..

That may explain why every now and then i get a bunch of 1's from it.