ReadPin

Nicholas Bott

This is probably going to sound really stupid; but, I can't seem to get a pin to read when I send positive current to it. I'm not even sure if that's the approach I should be using. Here is my scenario:

I wrote a nifty class for the littleStepU component. While the component is in operation it sends a busy signal. The busy signal is a 5v load on a busy pin on the component. I need to be able to read this value when it's high. I tried setting a microcontroller pin for input and using ReadPin - I think the code is good; but my circuit is bad.

Can you describe a basic circuit to read from that busy pin? Note: the busy pin shares the same circuit as the stamp, it's not isolated.

Also, Peter (since you'll probably be the one who answers this), your help with the DC-16 class was invaluable when I wrote a class to communicate with the littleStepU component, so thanks a lot for your help!

Peter Verkaik

If that busy pin outputs a low (0V) or high (5V) signal, then you
can directly, or via a 1k resistor, connect the busy pin to a javelin i/o pin.
If the busy pin happens to be an open collector, then you need a pullup
resistor to 5V. This pullup may also be present in case it is not an
open collector.
The circuit that should work in all cases:

····························+5V
···························· |
···························[noparse][[/noparse]10k]
·····························|
device busy pin o----[noparse][[/noparse]1k]----+

---

o javelin i/o pin
device gnd o

---

o javelin gnd

In your javelin program use

CPU.setInput(CPU.pin0);
CPU.readPin(CPU.pin0);

regards peter