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stewc
Guest
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| Simple question about port i/o |
 Posted: Wed Jan 16, 2008 6:20 pm |
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HI,
I have written a very simple program to turn all the port bits on for the 12F509. But when I run it in MPLAB I cant get GP2 to turn on. I was wondering if this is some strange querk in MPLAB or is there something wrong with my program?? I'm beginning to tear my hair out!!
| Code: | // Version 1.00
//
//
//********************************************************
#include "12F509.h"
#fuses INTRC,NOWDT,NOPROTECT,NOPROTECT,NOMCLR
#use delay(clock=4000000
void main(void)
{
/********************************************************
Initilisation
*********************************************************/
set_tris_b(0x00); //Set PORT all output
/*******************************************************
Main
********************************************************/
output_high(pin_b0);
output_high(pin_b1);
output_high(pin_b2);
output_high(pin_b3);
output_high(pin_b4);
output_high(pin_b5);
} |
TIA |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Jan 16, 2008 7:14 pm |
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| Quote: |
output_high(pin_b0);
output_high(pin_b1);
output_high(pin_b2);
output_high(pin_b3);
output_high(pin_b4);
output_high(pin_b5);
I cant get GP2 to turn on |
You probably mean GP3. It can't be done because that's an input-only
pin. |
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Guest
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| Posted: Thu Jan 17, 2008 2:24 am |
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No, its GP2 & GP3. I know GP3 cant be outputted as it is configured as input only.
I still cant get this to work????? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Jan 17, 2008 2:46 am |
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It's probably because the T0CS bit in the OPTION register is set to 1.
Use the set_options() macro to change the OPTION register so that
bit is set to 0. Example:
Add the set_options() macro above main(), and then call it at the
start of your program. See the 12F509 data sheet for an explanation
of the bits in the OPTION register.
| Code: |
#define set_options(value) {#ASM \
MOVLW value \
OPTION \
#ENDASM}
void main()
{
set_options(0xC0); // Allow use of GP2 for i/o
// Put the rest of your program here.
while(1); // Prevent PIC from going to sleep. Important !
} |
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Guest
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| Posted: Thu Jan 17, 2008 3:49 am |
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Thanks for that, works fine now.  |
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stewc
Guest
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| Posted: Thu Jan 17, 2008 8:00 am |
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I am making progress but have encountered another problem
Here is my code
| Code: | #include "12F509.h"
#use fast_io(B)
#fuses INTRC,NOWDT,PROTECT,NOPROTECT,MCLR
#use delay(clock=4000000)
#define set_options(value) {#ASM \
MOVLW value \
OPTION \
#ENDASM}
#define ENABLEPULLUPS (0)
#define DISABLEPULLUPS (128)
void main(void)
{
/******************************************************************************
Initilisation
******************************************************************************/
SETUP_TIMER_0(RTCC_DIV_1 | ENABLEPULLUPS); //Work around to enable pullups
set_options(0x80); // Allow use of GP2 for i/o
set_tris_b(0x3A); //Set PORT to desired I/O
/******************************************************************************
Main
******************************************************************************/
while(1)
{
output_bit(PIN_B2,input(PIN_B1));
output_bit(PIN_B0,input(PIN_B3));
}
}
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The program doesnt read B3 properly and subsequently wont output to B0
If I change B3 to B1 it works fine.
I have built a simple test circuit to test this. a switch to GND off B1 and B3 and 2 LEDs off B0 and B2. B3 is normally high (pullups enabled) and goes low when I press the button but it doesnt read it properly.
I cant see what is wrong |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Jan 17, 2008 5:49 pm |
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| Quote: |
The program doesnt read B3 properly.
#fuses INTRC,NOWDT,PROTECT,NOPROTECT,MCLR
|
Whenever a pin doesn't work as expected, it's probably because it
has not been configured to work in the desired mode.
Download the 12F509 data sheet and look at this table (on page 13 in
the Acrobat reader):
| Quote: | | TABLE 3-2: PIC12F508/509 PINOUT DESCRIPTION |
It shows the three possible modes that the GP3 pin can be in.
http://ww1.microchip.com/downloads/en/DeviceDoc/41236D.pdf
One of them is programming mode, which is not relevant. The other
two modes are: GP3 can either be an input pin or it can be the MCLR pin.
These two modes are controlled by Config bits (CCS calls them fuses).
You can see a list of the fuse settings at the top of the 12F509.H file.
| Quote: | | /////// Fuses: LP,XT,INTRC,RC,NOWDT,WDT,PROTECT,NOPROTECT,NOMCLR,MCLR |
Here's the file location:
| Quote: | | c:\Program Files\picc\Devices\12F509.h |
By looking at that table in the data sheet, and the list of fuse settings,
you should be able to figure out how to fix the problem. |
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