Reading Port Pins

Hi All,

This may be a dumb question......Is it standard practice that when you want to read either a 1 or a 0 from a port pin that an A/D must be used?

wuchy143 said:

Hi All,

This may be a dumb question......Is it standard practice that when you want to read either a 1 or a 0 from a port pin that an A/D must be used?

Click to expand...

No, not standard practice, and not even a practice at all - you just use a digital input pin.

wuchy143 said:

Hi All,

This may be a dumb question......Is it standard practice that when you want to read either a 1 or a 0 from a port pin that an A/D must be used?

Click to expand...

If you want to read either a 1 or a 0 from an input pin, you simply have the external hardware set the input high or low, then read the input pin. The most common way of doing this is to use a pull up resistor between the input pin and the positive side of the supply, then use a switch to ground the input pin to input a 0 and unground the input pin to input a 1. You can even use a transistor with the collector/emitter junction between the input pin and ground, then use a digital source to pulse the base of the transistor high and low.

If the source of said input is an analog source, then an A/D converter must be used.

Jon Wilder said:

...
If the source of said input is an analog source, then an A/D converter must be used.

Click to expand...

But not if all you want to do is quantize it to a 1 or a 0. An input set to digital mode will have a trip point of ~2V. Crude, but works.

If you want a programmable trip point, then use an analog comparator (not all PICs have these).