LED timing

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- 26th June 2008, 23:40
elen-group

LED timing

Hi,
We are trying to program our PIC 16F88 so that we can time our LED when triggered by a switch. We want the LED to stay on for five seconds everytime the switch is turned on.
This is the code we have so far:
'---------------------
DEFINE OSC 20

TRISB = %00000000 'setup PORTB; 0 for output, 1 for input
TRISA.0=1

loop:

IF PORTA.0 = 1 Then ledon
PORTB.0=0 'turn off LED

GOTO loop

ledon:

PORTB.0=1 'light LED
PAUSE 5000 'pause for 2 seconds
PORTB.0=0 'turn off LED
GOTO loop

END
'------------------------------------------

We have connected the switch to port A0 and the led to port B0. We would appreciate any help.
- 27th June 2008, 01:40
Archangel

Hello elen-group,
this should get you started:
ADCON0 = 0
ADCON1=0
CMCON = 7
ANSEL = 0
edit: pause 5000 = 5 seconds
- 27th June 2008, 02:58
skimask

Quote:

Originally Posted by elen-group

We have connected the switch to port A0 and the led to port B0. We would appreciate any help.

So, what's the problem?
- 27th June 2008, 20:48
elen-group

Our circuit is not conditioned to the switch. Everytime we turn on the circuit our led comes on regardless if we use the switch or not. We tried the suggested help but still did not fix it. I am thinking that there is some issue with the if statement which is not implementing the switch we want.
- 27th June 2008, 21:11
Archangel

Quote:

Originally Posted by elen-group

Our circuit is not conditioned to the switch. Everytime we turn on the circuit our led comes on regardless if we use the switch or not. We tried the suggested help but still did not fix it. I am thinking that there is some issue with the if statement which is not implementing the switch we want.

Code:

DEFINE OSC 20 PortA = %00000000 TRISB = %00000000 'setup PORTB; 0 for output, 1 for input TRISA.0=1 loop: IF PORTA.0 = 1 Then ledon PORTB.0=0 'turn off LED GOTO loop ledon: PORTB.0=1 'light LED PAUSE 5000 'pause for 2 seconds PORTB.0=0 'turn off LED GOTO loop END

put a pulldown resistor on porta.0
and a pullup on PortB.0
- 28th June 2008, 10:51
sayzer

Here, I think, what is needed.

Code:

'All the usual stuff here. '.... '.... '.... Sw VAR PORTA.0 ' Switch is connected to RA0. LED VAR PORTB.0 ' LED is connected to RB0. Flag VAR BIT ' Use a flag to have a virtual falling-edge,rising-edge thingie. Begin: INPUT Sw ' Switch pin is an input pin. Tie it to V+ with a resistor. Flag = 0 Loop: ' When button is pressed, the LED turns ON, stays ON 5 secs and then turns OFF. ' While button is being pressed, the led does NOT repeat Turn ON action. ' When the button is released then Flag is cleared. Thus, what happens? IF Sw = 0 AND Flag = 0 THEN LedOn ' SW is pressed. IF Sw = 1 AND Flag = 1 THEN Flag = 0 ' SW is released. GOTO Loop LedOn: LED = 1 ' Turn ON led. PAUSE 5000 ' Wait 5 secs. LED = 0 ' Turn OFF Led. Flag = 1 GOTO Loop END