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change_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 change notification interrupt
34 to detect switch bounce.
35 */
36 
37 volatile uint8_t bcnt;
38 //Interrupt Service Routine for Change Notification
39 void _ISRFAST _CNInterrupt (void) {
40  _CNIF = 0; //clear the change notification interrupt bit
41  bcnt++; //increment the bounce count
42 }
43 
44 
45 #define SW1 _RB13 //switch state
46 #define SW1_PRESSED() (SW1==0) //switch test
47 #define SW1_RELEASED() (SW1==1) //switch test
48 /// Switch1 configuration
49 inline void CONFIG_SW1() {
50  CONFIG_RB13_AS_DIG_INPUT(); //use RB13 for switch input
51  ENABLE_RB13_PULLUP(); //enable the pullup
52  ENABLE_RB13_CN_INTERRUPT(); //CN13IE = 1
53 }
54 
55 int main (void) {
56  configBasic(HELLO_MSG);
57  /** Configure the switch ***********/
58  CONFIG_SW1(); //enables individual CN interrupt also
59  /** Configure Change Notification general interrupt */
60  _CNIF = 0; //Clear the interrupt flag
61  _CNIP = 2; //Choose a priority
62  _CNIE = 1; //enable the Change Notification general interrupt
63  while (1) {
64  bcnt = 0;
65  outString("Press & release switch... ");
66  while (SW1_RELEASED());
68  while (SW1_PRESSED());
70  if (bcnt != 2) outString("..bounced: ");
71  else outString("..no bounce: ");
72  outUint8(bcnt);
73  outString("\n");
74  }
75 }