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int0_bounce.c
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1 /*
2  * "Copyright (c) 2008 Robert B. Reese, Bryan A. Jones, J. W. Bruce ("AUTHORS")"
3  * All rights reserved.
4  * (R. Reese, reese_AT_ece.msstate.edu, Mississippi State University)
5  * (B. A. Jones, bjones_AT_ece.msstate.edu, Mississippi State University)
6  * (J. W. Bruce, jwbruce_AT_ece.msstate.edu, Mississippi State University)
7  *
8  * Permission to use, copy, modify, and distribute this software and its
9  * documentation for any purpose, without fee, and without written agreement is
10  * hereby granted, provided that the above copyright notice, the following
11  * two paragraphs and the authors appear in all copies of this software.
12  *
13  * IN NO EVENT SHALL THE "AUTHORS" BE LIABLE TO ANY PARTY FOR
14  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
15  * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE "AUTHORS"
16  * HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
17  *
18  * THE "AUTHORS" SPECIFICALLY DISCLAIMS ANY WARRANTIES,
19  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
20  * AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
21  * ON AN "AS IS" BASIS, AND THE "AUTHORS" HAS NO OBLIGATION TO
22  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS."
23  *
24  * Please maintain this header in its entirety when copying/modifying
25  * these files.
26  *
27  *
28  */
29 
30 #include "pic24_all.h"
31 
32 /** \file
33  * Demonstrates the use of int0 interrupt
34  * to detect switch bounce.
35  *
36  *
37  */
38 
39 //Interrupt Service Routine for INT0
40 volatile uint8_t u8_bcnt;
41 void _ISRFAST _INT0Interrupt (void) {
42  _INT0IF = 0; //clear the interrupt bit
43  u8_bcnt++; //increment the bounce count
44 }
45 
46 #define SW1 _RB7 //switch state
47 #define SW1_PRESSED() (SW1==0) //switch test
48 #define SW1_RELEASED() (SW1==1) //switch test
49 /// Switch1 configuration, RB7 shares INT0 pin on PIC24HGP202
50 inline void CONFIG_SW1() {
51  CONFIG_RB7_AS_DIG_INPUT(); //use RB7 for switch input
52  ENABLE_RB7_PULLUP(); //enable the pullup
53 }
54 
55 
56 int main (void) {
57  uint8_t u8_cnt;
58  configBasic(HELLO_MSG);
59  /** Configure the switch ***********/
60  CONFIG_SW1(); //enables individual CN interrupt also
61  DELAY_US(1);
62  /** Configure INT0 interrupt */
63  _INT0IF = 0; //Clear the interrupt flag
64  _INT0IP = 2; //Choose a priority
65  _INT0EP = 1; //negative edge triggerred
66  _INT0IE = 1; //enable INT0 interrupt
67  while (1) {
68  u8_bcnt = 0;
69  outString("Press & release switch... ");
70  while (SW1_RELEASED());
72  while (SW1_PRESSED());
74  u8_cnt = u8_bcnt; //copy variable so will not change
75  if (u8_cnt != 1) outString("..bounced: ");
76  else outString("..no bounce: ");
77  outUint8(u8_cnt);
78  outString("\n");
79  }
80 }