PIC16F628a Schmitt Trigger Input

How would I program and wire a circuit to use a toggle switch on RA5? I've been unable to get it to work.

~ Dave

Quote:

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Originally Posted by yankee

How would I program and wire a circuit to use a toggle switch on RA5? I've been unable to get it to work.

~ Dave

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Hi Dave, . . . use a toggle switch . . . do you mean as an input or toggle as an output ? This chip will not output on RA5, so I will assume as an input. A simple if then loop to check port status will do fine. Schmitt trigger has higher and lower readings than TTL to switch say 1volt and 4 volt as opposed to about 1/2 supply voltage.

Code:

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IF PortA.5 THEN

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I haven't tried this yet. Does this look like it will work?

Code:

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@ device  pic16F628A, INTRC_OSC_NOCLKOUT, wdt_off, mclr_off, lvp_off, protect_off


TRISA = %00000100                                                        ' Make all port a pins inputs except for 5
TRISB = %00000000                                                        ' Make port b pins outputs

B15 VAR PORTB.7

switch:

if porta.5 = 0 then cal
if porta.5 = 1 then main

goto switch

cal:

low B15
pause 3000  ' pause 3 seconds
HIGH B15
pause 3000
if porta.5 = 0 then cal

goto switch

main:

IC performs main routine

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Quote:

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Originally Posted by yankee

I haven't tried this yet. Does this look like it will work?

Code:

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@ device  pic16F628A, INTRC_OSC_NOCLKOUT, wdt_off, mclr_off, lvp_off, protect_off


TRISA = %00000100                                                        ' Make all port a pins inputs except for 5
TRISB = %00000000                                                        ' Make port b pins outputs

B15 VAR PORTB.7

switch:

if porta.5 = 0 then cal
if porta.5 = 1 then main

goto switch

cal:

low B15
pause 3000  ' pause 3 seconds
HIGH B15
pause 3000
if porta.5 = 0 then cal

goto switch

main:

IC performs main routine

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I would probably do as follows:

Code:

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@ device  pic16F628A, INTRC_OSC_NOCLKOUT, wdt_off, mclr_off, lvp_off, protect_off
PortA = %00000000    ' set ports to known state
PortB = %00000000    ' outputs will initialize in low state

TRISA = %00100000 ' Make all port a pins outputs except for 5
TRISB = %00000000 ' Change PortB from HI Q to Outputs that will initialize low
       
i VAR BYTE ' counter variable
cmcon = 7  ' disable comparators
Switch:
    IF PortA.5 = 1 THEN Main
    PortB.7 = 0
    FOR i = 1 TO 30
    pause 100  ' pause 100 ms 30 times
    NEXT i
    PortB.7 = 1
    FOR i = 1 TO 30
    pause 100
    NEXT i
GOTO Switch

main:
              ' do your main stuff here

goto switch  ' go back to switch and check


end

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I would change the pauses in case you need to interrupt the code,
and remove redundant loops

Thanks Joe! That worked really slick. Now, I just have to figure out why your code works so well. I could definitely use a code for Dummies book. I'm not understanding the "FOR i = 1 TO 30."

~ Dave