Light up led source code - what went wrong ?

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evaang2003

Joined: 28 May 2009
Posts: 14

09 Jun 2009 7:10 light up led source code

hi, i currently play with led using pic16f877a.
i connect one led to port b bit7.
the result i want to get is just to lit the led.
however, it does not response.
here is the source code i write using ccs picc compiler.

#include <16f877a.h>

void main()
{
output_high(PIN_B7);
}

can anybody tell me what went wrong?

xxtigerxx

Joined: 05 Jun 2001
Posts: 240
Helped: 5
Location: Greece

09 Jun 2009 7:28 light up led source code

you must make the B7 output..

TRISB7=0;

after

PB7=1;

saeed_pk

Joined: 20 May 2006
Posts: 199
Helped: 5
Location: Islamabad, Pakistan

09 Jun 2009 8:15 light up led source code

Yes you have to clear the the TRISB7 bit to make this pin output make sure about CONFIG word if DEBUG is enabled this pin may not function.

bld

Joined: 25 Jul 2006
Posts: 54
Helped: 7
Location: Iasi, Romania

09 Jun 2009 8:47 Re: light up led source code

I would suggest:

Code:

#include <16f877a.h>

void main()
{
output_high(PIN_B7);
while(1);
}

In your code, after the the LED is on, the microcontroler reaches the end of the program and resests. So the result will be a blinking of the LED with a very small duty factor and maybe that's why you can't see any light.

I've never used CCS compiler but maybe you need to set pin RB7 as output separately before putting it high.

evaang2003

Joined: 28 May 2009
Posts: 14

10 Jun 2009 4:43 Re: light up led source code

well, i modify the code to:

#include<16f877a.h>

#BYTE PORTB=0x06
#BIT PORTB7=PORTB.7

void main(void)
{
set_tris_b(0x00);
output_high(PIN_B7);
while(1);
}

sadly, it din work:(

xxtigerxx

Joined: 05 Jun 2001
Posts: 240
Helped: 5
Location: Greece

10 Jun 2009 6:20 light up led source code

can you tell me which compiler you r using?

maybe your problem is hardware..

Try run in simulation. it works?

bld

Joined: 25 Jul 2006
Posts: 54
Helped: 7
Location: Iasi, Romania

10 Jun 2009 8:11 Re: light up led source code

I can't see in your code if you set the configuration bits of the controller, especially the oscillator configuration...

evaang2003

Joined: 28 May 2009
Posts: 14

10 Jun 2009 9:49 Re: light up led source code

i just want to test the i/o function of pic16f877a.
i experiment it with one led, 4MHz oscilator but it din work.
i m using ccs compiler.

i then include these into source code but it din work.
#use dalay(clock=4000000)// 4MHz crytal is used.

it din work.
why???

jumper2high

Joined: 24 May 2009
Posts: 62
Helped: 3
Location: Serbia

10 Jun 2009 12:45 Re: light up led source code

What exactly are you expecting the LED to do?
The way you created it, the moment the chip gets power it'll turn the LED on and that's it. If you want it to blink, you'll need to turn it on, wait and then turn it off. You do this by using a delay function, usually called DelayMs(X) where X is the number of milliseconds you want to wait.

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10 Jun 2009 12:45 Ads

evaang2003

Joined: 28 May 2009
Posts: 14

11 Jun 2009 3:11 Re: light up led source code

i now know the fatal error that occur.
my compiler is damaged that it generate rubbish hex code.

thanks for those try to help me.
i will work it on after i get the new compiler.