[PIC] Use RA4 input as impulse input

[dahmano]

Hi,
I use PIC16F84A.
I want to use the RA4 input as a pulse input, instead of RB0
is it possible or not?
frequency between 1Hz and 300Hz,
thank you

 

[KlausST]

Hi,

is it possible or not?

for sure it is possible.

in detail it depends on
* voltage levels
* and how you want to process the pulses.

Klaus

 

[Aussie Susan]

Let me guess - you were using RB0 because of the external 'INT' (interrupt). On that device you can't reassign functions to pins so you will need to use some other technique to detect the changes. It might be a little easier as you can only use the INT signal to detect either a raising edge or a falling edge (i.e. you can detect that a pulse appears but not how long for).
RA4 does NOT have 'interrupt on change' capability so any pulse detection (i.e. change of state on the pin) will have to come from you constantly monitoring the state of the pin and detecting the changes in software - won't let your MCU do much else then!
So yes, it is possible but there are many, MANY other factors that need to be taken into account before you can decide if it is practical.
Susan

 

[dahmano]

input help RA4 PIC16F84A

Hi,
I want to use the input RA4 input.
I try several times I can not activate it.
to realize a led tachometer.
I am looking for a code example that uses this input RA4 on pic16f84.
frequency between 1 Hz to 300 Hz,
max.
Thank you.

 

[betwixt]

Show us your code so far and we will try to find the problem. Also tell us which compiler or assembler you are using.

Brian.

 

[baileychic]

RA4 is a open drain pin.

 

[betwixt]

RA4 is a open drain pin.

Makes no difference, it still works as an input.

Brian.