Is there an IC that does this? (switches)

[out_of_my_depth]

Hi, I need a device that takes upto 4 separate input signals and, using pulses from a 5th input, connects the 4 inputs (one at a time) to a single output pin.

What i'm trying to do is time the pwm pulses from 4 channels of an rc model rx unit using only two IO ports on a PIC.

Can sometime tell me if such a device exists and, if so, what it's called.

Thanks

 

[evandude]

a multiplexer will allow you to access multiple inputs with just one input pin on the microcontroller. however, as far as I know you can't get any that can cycle through the inputs with just one I/O pin... but since you only need to access 4 inputs, you could do it with two output pins for addressing.

if you REALLY need it to only use two pins, then you could build another circuit from some flip-flops that cycles through the 4 addresses you need (00,01,10,11) with input pulses from your one output pin. (simple binary counter)

or if you don't mind overkill, bear in mind that an 8-pin PIC has 6 I/O pins, exactly enough to handle the 4 servo inputs, 1 pulse input, and 1 output that you need... and it would be very simple to whip up a program to handle it (and at a 1 uS instruction time with the 4MHz internal oscillator, you probably wouldn't lose any significant accuracy versus a hardware solution...)

 

[out_of_my_depth]

multiplexer it is then. Cheers.

For info, pins are at a premium but more important is the need to use a single input to the PIC.

/edit

I've had a search round my fav components site and can't find anything that resembles what what you describe. Might it be called something else? (I'm in the UK) do you have a link I could follow?

edit/

 

[out_of_my_depth]

found 'em. They're called 'Data Selectors' on the site I use. They appear to be exactly what you said. Thanks again.