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 |
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12 | #include <stdint.h>
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13 | #include <avr/io.h>
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14 | #include <avr/interrupt.h>
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15 |
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16 | #ifndef F_CPU
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17 | #define F_CPU 1000000 // processor clock frequency
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18 | #warning kein F_CPU definiert
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19 | #endif
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20 |
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21 | #define KEY_DDR DDRB
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22 | #define KEY_PORT PORTB
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23 | #define KEY_PIN PINB
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24 | #define KEY0 0
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25 | #define KEY1 1
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26 | #define KEY2 2
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27 | #define ALL_KEYS (1<<KEY0 | 1<<KEY1 | 1<<KEY2)
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28 |
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29 | #define REPEAT_MASK (1<<KEY1 | 1<<KEY2) // repeat: key1, key2
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30 | #define REPEAT_START 50 // after 500ms
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31 | #define REPEAT_NEXT 20 // every 200ms
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32 |
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33 | #define LED_DDR DDRA
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34 | #define LED_PORT PORTA
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35 | #define LED0 0
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36 | #define LED1 1
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37 | #define LED2 2
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38 |
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39 | volatile uint8_t key_state; // debounced and inverted key state:
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40 | // bit = 1: key pressed
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41 | volatile uint8_t key_press; // key press detect
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42 |
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43 | volatile uint8_t key_rpt; // key long press and repeat
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44 |
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45 |
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46 | ISR( TIMER0_OVF_vect ) // every 10ms
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47 | {
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48 | static uint8_t ct0, ct1, rpt;
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49 | uint8_t i;
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50 |
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51 | TCNT0 = (uint8_t)(int16_t)-(F_CPU / 1024 * 10e-3 + 0.5); // preload for 10ms
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52 |
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53 | i = key_state ^ ~KEY_PIN; // key changed ?
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54 | ct0 = ~( ct0 & i ); // reset or count ct0
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55 | ct1 = ct0 ^ (ct1 & i); // reset or count ct1
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56 | i &= ct0 & ct1; // count until roll over ?
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57 | key_state ^= i; // then toggle debounced state
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58 | key_press |= key_state & i; // 0->1: key press detect
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59 |
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60 | if( (key_state & REPEAT_MASK) == 0 ) // check repeat function
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61 | rpt = REPEAT_START; // start delay
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62 | if( --rpt == 0 ){
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63 | rpt = REPEAT_NEXT; // repeat delay
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64 | key_rpt |= key_state & REPEAT_MASK;
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65 | }
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66 | }
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67 |
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68 | ///////////////////////////////////////////////////////////////////
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69 | //
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70 | // check if a key has been pressed. Each pressed key is reported
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71 | // only once
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72 | //
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73 | uint8_t get_key_press( uint8_t key_mask )
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74 | {
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75 | cli(); // read and clear atomic !
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76 | key_mask &= key_press; // read key(s)
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77 | key_press ^= key_mask; // clear key(s)
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78 | sei();
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79 | return key_mask;
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80 | }
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81 |
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82 | ///////////////////////////////////////////////////////////////////
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83 | //
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84 | // check if a key has been pressed long enough such that the
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85 | // key repeat functionality kicks in. After a small setup delay
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86 | // the key is reported beeing pressed in subsequent calls
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87 | // to this function. This simulates the user repeatedly
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88 | // pressing and releasing the key.
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89 | //
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90 | uint8_t get_key_rpt( uint8_t key_mask )
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91 | {
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92 | cli(); // read and clear atomic !
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93 | key_mask &= key_rpt; // read key(s)
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94 | key_rpt ^= key_mask; // clear key(s)
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95 | sei();
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96 | return key_mask;
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97 | }
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98 |
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99 | ///////////////////////////////////////////////////////////////////
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100 | //
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101 | uint8_t get_key_short( uint8_t key_mask )
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102 | {
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103 | cli(); // read key state and key press atomic !
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104 | return get_key_press( ~key_state & key_mask );
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105 | }
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106 |
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107 | ///////////////////////////////////////////////////////////////////
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108 | //
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109 | uint8_t get_key_long( uint8_t key_mask )
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110 | {
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111 | return get_key_press( get_key_rpt( key_mask ));
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112 | }
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113 |
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114 | int main( void )
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115 | {
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116 | LED_PORT = 0xFF;
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117 | LED_DDR = 0xFF;
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118 |
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119 | // Configure debouncing routines
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120 | KEY_DDR &= ~ALL_KEYS; // configure key port for input
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121 | KEY_PORT |= ALL_KEYS; // and turn on pull up resistors
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122 |
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123 | TCCR0 = (1<<CS02)|(1<<CS00); // divide by 1024
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124 | TCNT0 = (uint8_t)(int16_t)-(F_CPU / 1024 * 10e-3 + 0.5); // preload for 10ms
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125 | TIMSK |= 1<<TOIE0; // enable timer interrupt
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126 |
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127 | sei();
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128 |
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129 | while(1){
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130 | if( get_key_short( 1<<KEY1 ))
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131 | LED_PORT ^= 1<<LED1;
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132 |
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133 | if( get_key_long( 1<<KEY1 ))
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134 | LED_PORT ^= 1<<LED2;
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135 |
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136 | // single press and repeat
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137 |
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138 | if( get_key_press( 1<<KEY2 ) || get_key_rpt( 1<<KEY2 )){
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139 | uint8_t i = LED_PORT;
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140 |
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141 | i = (i & 0x07) | ((i << 1) & 0xF0);
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142 | if( i < 0xF0 )
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143 | i |= 0x08;
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144 | LED_PORT = i;
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145 | }
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146 | }
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147 | }
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