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steve_smith94
Joined: 21 Mar 2011
Posts: 7
Location: London
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| How to configure IOC on PIC16F917 |
 Posted: Mon Mar 21, 2011 5:22 am |
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Hi,
I'm a PIC newbie and have been given a circuit and asked to write the software.
I need to recognise a High (5v) on either RB6 and RB7, provided by a momentary push button switch. Then run code dependant upon which button is switch.
I have tried all the examples i can find on configuring the interrupts and can't seem to get it to work.
One obvious problem is that I'm unable to use pullups on port B as I need to trigger on a high.
Any pointers would be most welcome. |
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temtronic
Joined: 01 Jul 2010
Posts: 9229
Location: Greensville,Ontario
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| Posted: Mon Mar 21, 2011 6:03 am |
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Without seeing the code you wrote it's very hard to tell you what's wrong !
Could be your hardware setup, could be software...
Wrong or missing pulldown resistors, power supply incorrect,defective switches, bad wiring, just to start...
Sounds like you want a low-to-high interrupt. you will need debouncing on the pushbuttons.
The example that CCS supplies will work,the help file has an FAQ section. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Mar 21, 2011 1:18 pm |
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| Quote: | One obvious problem is that I'm unable to use pullups on port B as I need
to trigger on a high. |
But you control the source code. You can use positive logic or negative
logic. The C language is completely flexible with respect to that.
Here is the normal way to connect a push-button switch to a PIC:
| Code: |
+5v
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<
> 4.7K
< ___ Push button switch
To | _|_|_
PIC -----------------o o------
pin |
--- GND
-
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However, sometimes on PIC hobby websites, you will see it wired the
opposite way. When you press the switch, it connects the +5v Vdd voltage
to the PIC pin. I suspect you are looking at one of those websites.
This thread has links to several push-button switch example programs:
http://www.ccsinfo.com/forum/viewtopic.php?t=42285 |
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steve_smith94
Joined: 21 Mar 2011
Posts: 7
Location: London
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| Posted: Tue Mar 22, 2011 3:42 am |
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Thanks guys.
\My code is below
| Code: |
#include <16F917.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOPUT //No Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES MCLR //Master Clear pin enabled
#FUSES NOCPD //No EE protection
#FUSES NOBROWNOUT //No brownout reset
#FUSES IESO //Internal External Switch Over mode enabled
#FUSES FCMEN //Fail-safe clock monitor enabled
#FUSES NODEBUG //No Debug mode for ICD
#FUSES RESERVED //Used to set the reserved FUSE bits
#use delay(clock=20000000)
#include "C:\Documents and Settings\Smiths\Desktop\test\test1.h"
#include <float.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
short int dbutton6, dbutton7;
#int_RB
void RB_isr(void)
{
int current;
static int last=0;
set_tris_b(0xF0);
current=input_b();
if ((!bit_test(last,6))&&(bit_test(current,6)))
{
//b6 went High
dbutton6=1;
}
if ((!bit_test(last,7))&&(bit_test(current,7)))
{
//b7 went High
dbutton7=1;
}
delay_ms(10);
}
void clear_delta()
{
dbutton6=0;
dbutton7=0;
}
void main()
{
setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_CLOCK_DIV_2);
setup_spi(SPI_MASTER|SPI_L_TO_H|SPI_CLK_DIV_4);
setup_lcd(LCD_DISABLED);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
enable_interrupts(INT_RB);
enable_interrupts(GLOBAL);
clear_delta();
while(1)
{
output_bit(PIN_D0,0);
output_bit(PIN_D1,0);
output_bit(PIN_D2,0);
output_bit(PIN_D3,1);
output_bit(PIN_D4,0);
output_bit(PIN_D5,0);
output_bit(PIN_D6,0);
output_bit(PIN_D7,1);
delay_ms( 1000 ) ;
if(dbutton6)
{
output_bit(PIN_D0,1);
output_bit(PIN_D1,1);
output_bit(PIN_D2,0);
output_bit(PIN_D3,0);
output_bit(PIN_D4,1);
output_bit(PIN_D5,1);
output_bit(PIN_D6,0);
output_bit(PIN_D7,0);
//dbutton6=0;
delay_ms( 1000 ) ;
}
if(dbutton7)
{
output_bit(PIN_D0,0);
output_bit(PIN_D1,1);
output_bit(PIN_D2,1);
output_bit(PIN_D3,0);
output_bit(PIN_D4,0);
output_bit(PIN_D5,1);
output_bit(PIN_D6,1);
output_bit(PIN_D7,0);
//dbutton7=0;
delay_ms( 1000 ) ;
}
}
}
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All that happens is two 7 seg displays output figures dependant upon which switch is depressed( RB6 or RB7). Unfortunatly the hardware switches +5v 
There are no pull down resistors on the inputs. However, scoping the pind RB6 and RB7 the levels look good. But I will try to place some pull downs on the lines and report back with my findings.
Cheers |
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steve_smith94
Joined: 21 Mar 2011
Posts: 7
Location: London
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| Posted: Tue Mar 22, 2011 3:45 am |
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| Just one further question; what size pull downs would you suggest? 4k7 as per pull ups? |
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steve_smith94
Joined: 21 Mar 2011
Posts: 7
Location: London
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| Posted: Wed Mar 23, 2011 9:20 am |
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I have downloaded the real pic simulator to aid my getting to the bottom of this issue.
Using this configured for a PIC16F917, I can't get any of the examples I have seen to work.
Is there a ccs compiling issue for this PIC?
Does anyone have any ideas how I can get an int_rb interrupt to work with this PIC? I have now pulled down my 2 ports using a 10k res (still no joy). But seeing the simulator also doesn't work I guess that it must be a software issue.
Please help  |
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