2 PIC questions

[Electronics4you]

Hi All

Just a few minor PIC problems.

1. I have this code:

test1
btfss PORTA,0
goto test2
goto next1

test2
btfss PORTA,1
goto test3
goto next2

test3
btfss PORTA,2
goto test4
goto next3

test4
btfss PORTA,3
goto test1
goto next4

It's used as a scanningcode for 4 micro-switches. How can I store the values in variables so I can use them later on?

2. Can it be done in another way, so the scanning proces is faster?

__________________________________
Who can live without electronics - not me!

 

[eblc1388]

Your version works but you can try this shorter version:

test    btfsc PORTA,0   ; skip if portA,0 low
        goto next1        ; is high, go to handling routine
        btfsc PORTA,1
        goto next2
        btfsc PORTA,2
        goto next3
        btfsc PORTA,3
        goto next4
        goto test          ;loop until switch closure

It's used as a scanningcode for 4 micro-switches. How can I store the values in variables so I can use them later on?

You set a flag in each of the above next# entry.

2. Can it be done in another way, so the scanning proces is faster?

Four tests, total 8 instructions. Difficult to make it faster. On a PIC with a 20MHz crystal, the loop would take just 2uS to go around once. A switch closure is more like several mS and that's several thousand times slower than you can check them.

Why would you want the checking to be faster?

 

[atferrari]

No debouncing

If we are talking switches, some debouncing should be considered, I think.

**broken link removed**

 

[Exo]

Just write the main program so it only runs the switch checking code 5 times per second or so, that works very good for debouncing...

 

[Joel Rainville]

Re: No debouncing

If we are talking switches, some debouncing should be considered, I think.

**broken link removed**

Wow, that's a seriously good article. Thanks.

 

[eblc1388]

Re: No debouncing

Wow, that's a seriously good article. Thanks.

Then you'll find this one even better, by the same author.

http://www.ganssle.com/debouncing.pdf

 

[Electronics4you]

How can I get the bit-tests stored, so i can generate a function, when a combinations of 4 bits occur?

___________________________________
Life's good - isn't it?

 

[ChArLyZzZ]

in each routine of next#, u set the appropriate bit of a register, call it STATUS_SWITCH
i.e: next# bsf STATUS_SWITCH, #
...

at the end of your scanning, you subtract the value in STATUS_SWITCH by your desired set of combinations.
chill