1 | // ps/2 keyboard decoder on ATMega8, ATMega48
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2 | // Copyright 2010-2014, Adrien Destugues <pulkomandy@pulkomandy.tk>
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3 | // This file is distributed under the terms of the MIT Licence.
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4 |
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5 | // Parts borrowed from :
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6 | // keyboard.c
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7 | // for NerdKits with ATmega168
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8 | // hevans@nerdkits.com
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9 |
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10 | #include <avr/io.h>
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11 | #include <avr/interrupt.h>
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12 |
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13 |
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14 | //ps/2 Keyboard pin out
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15 | //pin 5 - clock
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16 | //pin 3 - GND
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17 | //pin 1 - data
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18 | //pin 4 - VCC
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19 |
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20 | //PIN configuration
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21 | #define PS2_PORT PIND
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22 | #define PS2_CLK PD3 /* Also INT1 */
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23 |
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24 | #ifdef __AVR_ATtiny2313__
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25 | // K4KUSB modified board
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26 | #define PS2_DATA PD5
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27 | #else
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28 | // ENSSAT IR modified board
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29 | #define PS2_DATA PD4
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30 | #endif
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31 |
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32 | static volatile uint8_t char_waiting;
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33 | static uint8_t started;
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34 | static uint8_t bit_count;
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35 | static uint8_t extended;
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36 |
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37 | volatile uint8_t kbd_data;
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38 | uint8_t release;
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39 |
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40 | // Interrupt vector - Triggered when there is activity on the clock line
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41 | ISR(INT1_vect)
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42 | {
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43 | //make sure clock line is low, if not ignore this transition
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44 | if(PS2_PORT & (1<<PS2_CLK)){
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45 | return;
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46 | }
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47 |
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48 | //if we have not started, check for start bit on DATA line
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49 | if(!started){
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50 | if ( (PS2_PORT & (1<<PS2_DATA)) == 0 ) {
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51 | started = 1;
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52 | bit_count = 0;
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53 | kbd_data = 0;
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54 | //printf_P(PSTR("%d"),started);
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55 | return;
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56 | }
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57 | } else if(bit_count < 8) { //we started, read in the new bit
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58 | //put a 1 in the right place of kdb_data if PC2 is high, leave
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59 | //a 0 otherwise
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60 | if(PS2_PORT & (1<<PS2_DATA)){
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61 | kbd_data |= (1<<bit_count);
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62 | }
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63 | bit_count++;
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64 | return;
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65 | } else if(bit_count == 8){ //pairty bit
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66 | //not implemented
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67 | bit_count++;
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68 | return;
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69 | } else { //stop bit
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70 | //should check to make sure DATA line is high, what to do if not?
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71 | started = 0;
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72 | bit_count = 0;
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73 | }
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74 |
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75 | if(kbd_data == 0xF0){ //release code
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76 | release = 1;
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77 | kbd_data = 0;
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78 | return;
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79 | } else { //not a special character
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80 | #ifdef CALLBACK
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81 | CALLBACK
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82 | #endif
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83 | if(release){ //we were in release mode - exit release mode
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84 | release = 0;
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85 | } else {
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86 | // Notify callback that there's a new char waiting
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87 | char_waiting = 1;
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88 | }
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89 | }
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90 | }
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91 |
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92 |
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93 | uint8_t read_char(){
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94 | while(!char_waiting);
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95 | char_waiting = 0;
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96 | return kbd_data;
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97 | }
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98 |
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99 |
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100 | void init_keyboard(){
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101 | started = 0;
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102 | kbd_data = 0;
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103 | bit_count = 0;
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104 |
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105 | //make PS2_CLK input pin
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106 | DDRD &= ~((1<<PS2_CLK) | (1<<PS2_DATA));
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107 | //turn on pullup resistor
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108 | PS2_PORT |= (1<<PS2_CLK);
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109 |
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110 | // FIXME we can use the "pin change" interrupt rather than INT0/INT1 when not
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111 | // on the old clumsy ATMega8. This would allow for any pin to be used.
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112 | // PCMSK |= (1<<PIND3);
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113 | MCUCR |= (1<<ISC11); // Falling edge
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114 | MCUCR &= ~(1<<ISC10);
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115 | #ifdef __AVR_ATmega48P__
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116 | EIMSK |= (1<<INT1);
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117 | #else // ATmega8
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118 | GIMSK |= (1<<INT1);
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119 | #endif
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120 |
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121 | sei();
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122 | }
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123 |
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124 |
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