1 | /************************************************************************/
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2 | /* */
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3 | /* Debouncing 8 Keys */
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4 | /* Sampling 4 Times */
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5 | /* With Repeat Function */
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6 | /* */
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7 | /* Author: Peter Dannegger */
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8 | /* danni@specs.de */
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9 | /* */
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10 | /************************************************************************/
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11 | // Target: ATMega48
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12 |
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13 | #include <io.h>
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14 | #include <interrupt.h>
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15 |
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16 | typedef unsigned char u8;
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17 | typedef signed short s16;
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18 |
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19 | #define XTAL 8000000L // 8MHz
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20 |
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21 | #define KEY_PIN PINB
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22 | #define KEY0 0
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23 | #define KEY1 1
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24 | #define KEY2 2
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25 | #define KEY3 3
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26 |
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27 | #define LED_DDR DDRC
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28 | #define LED_PORT PORTC
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29 | #define LED0 0
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30 | #define LED1 1
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31 | #define LED2 2
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32 |
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33 | #define REPEAT_MASK (1<<KEY3^1<<KEY2^1<<KEY1^1<<KEY0)
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34 | #define REPEAT_START 10 // after 100ms
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35 | #define REPEAT_NEXT 20 // every 200ms
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36 |
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37 | u8 key_state; // debounced and inverted key state:
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38 | // bit = 1: key pressed
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39 | u8 key_press; // key press detect
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40 |
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41 | u8 key_rpt; // key long press and repeat
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42 |
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43 |
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44 | ISR( TIMER0_COMPA_vect ) // every 10ms
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45 | {
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46 | static u8 ct0, ct1, rpt;
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47 | u8 i;
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48 |
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49 | i = key_state ^ ~KEY_PIN; // key changed ?
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50 | ct0 = ~( ct0 & i ); // reset or count ct0
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51 | ct1 = ct0 ^ (ct1 & i); // reset or count ct1
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52 | i &= ct0 & ct1; // count until roll over ?
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53 | key_state ^= i; // then toggle debounced state
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54 | key_press |= key_state & i; // 0->1: key press detect
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55 |
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56 | if( (key_state & REPEAT_MASK) == 0 ) // check repeat function
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57 | rpt = REPEAT_START; // start delay
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58 | if( --rpt == 0 ){
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59 | rpt = REPEAT_NEXT; // repeat delay
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60 | key_rpt |= key_state & REPEAT_MASK;
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61 | }
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62 | }
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63 |
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64 |
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65 |
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66 | u8 get_key_press( u8 key_mask )
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67 | {
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68 | cli(); // read and clear atomic !
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69 | key_mask &= key_press; // read key(s)
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70 | key_press ^= key_mask; // clear key(s)
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71 | sei();
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72 | return key_mask;
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73 | }
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74 |
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75 | u8 get_key_rpt( u8 key_mask )
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76 | {
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77 | cli(); // read and clear atomic !
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78 | key_mask &= key_rpt; // read key(s)
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79 | key_rpt ^= key_mask; // clear key(s)
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80 | sei();
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81 | return key_mask;
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82 | }
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83 |
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84 | u8 get_key_short( u8 key_mask )
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85 | {
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86 | cli(); // read key state and key press atomic !
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87 | return get_key_press( ~key_state & key_mask );
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88 | }
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89 |
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90 | u8 get_key_long( u8 key_mask )
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91 | {
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92 | return get_key_press( get_key_rpt( key_mask ));
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93 | }
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94 |
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95 | int main( void )
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96 | {
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97 | TCCR0A = 1<<WGM01; // Mode 2: CTC
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98 | TCCR0B = 1<<CS02^1<<CS00; // divide by 1024
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99 | OCR0A = (s16)(XTAL / 1024.0 * 10e-3 - 0.5); // preload for 10ms
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100 | TIMSK0 = 1<<OCIE0A; // enable timer interrupt
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101 |
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102 | LED_PORT = 0xFF;
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103 | LED_DDR = 0xFF;
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104 | sei();
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105 |
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106 | for(;;){ // main loop
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107 |
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108 | switch( get_key_long( 1<<KEY1^1<<KEY0 )){
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109 |
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110 | case 1<<KEY0: LED_PORT ^= 1<<LED0; break;
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111 |
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112 | case 1<<KEY1: LED_PORT ^= 1<<LED1; break;
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113 |
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114 | case 1<<KEY1^1<<KEY0: LED_PORT ^= 1<<LED2; break;
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115 | }
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116 |
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117 | switch( get_key_rpt( 1<<KEY3^1<<KEY2 )){
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118 |
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119 | case 1<<KEY2: LED_PORT ^= 1<<LED0; break;
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120 |
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121 | case 1<<KEY3: LED_PORT ^= 1<<LED1; break;
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122 |
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123 | case 1<<KEY3^1<<KEY2: LED_PORT ^= 1<<LED2; break;
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124 | }
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125 | }
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126 | }
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