Tutorial: How to Use Arduino Uno as HID | Part 1: Arduino Keyboard Emulation

  1
  2uint8_t buf[8] = {
  3  0
  4};  // Keyboard Report Buffer: 8 bytes
  5
  6#define PIN_W A0
  7#define PIN_A A1
  8#define PIN_S A2
  9#define PIN_D A3
 10
 11//#define SERIAL_DEBUG  // for serial debug: remove //
 12                        // for actual HID: put //
 13
 14bool currState_W = HIGH;
 15bool currState_A = HIGH;
 16bool currState_S = HIGH;
 17bool currState_D = HIGH;
 18          
 19bool prevState_W = HIGH; 
 20bool prevState_A = HIGH; 
 21bool prevState_S = HIGH; 
 22bool prevState_D = HIGH; 
 23
 24unsigned long prevTime_W = 0;
 25unsigned long prevTime_A = 0;
 26unsigned long prevTime_S = 0;
 27unsigned long prevTime_D = 0;
 28
 29unsigned long waitTime_W = 50;
 30unsigned long waitTime_A = 50;
 31unsigned long waitTime_S = 50;
 32unsigned long waitTime_D = 50;
 33
 34void setup() 
 35{
 36  Serial.begin(9600);
 37
 38  pinMode(PIN_W, INPUT_PULLUP);
 39  pinMode(PIN_A, INPUT_PULLUP);
 40  pinMode(PIN_S, INPUT_PULLUP);
 41  pinMode(PIN_D, INPUT_PULLUP);
 42  
 43  delay(200);
 44}
 45
 46void loop() 
 47{
 48  checkButton();
 49}
 50
 51
 52void checkButton() {
 53
 54  bool currRead_W = digitalRead(PIN_W);
 55  bool currRead_A = digitalRead(PIN_A);
 56  bool currRead_S = digitalRead(PIN_S);
 57  bool currRead_D = digitalRead(PIN_D);
 58
 59  if (currRead_W != prevState_W) {
 60    prevTime_W = millis();
 61  }
 62  if (currRead_A != prevState_A) {
 63    prevTime_A = millis();
 64  }
 65  if (currRead_S != prevState_S) {
 66    prevTime_S = millis();
 67  }
 68  if (currRead_D != prevState_D) {
 69    prevTime_D = millis();
 70  }
 71
 72  if ((millis() - prevTime_W) > waitTime_W) {
 73    if (currRead_W != currState_W) {
 74      currState_W = currRead_W;
 75      if (currState_W == LOW) {
 76        // Send the code
 77        buf[2] = 26;    // HID: W key
 78#ifdef SERIAL_DEBUG
 79        buf[2] = 'W';     // Serial: W key
 80#endif
 81        Serial.write(buf, 8); // Send keypress
 82      } else {
 83        // Release the keyboard
 84        releaseKey();
 85      }
 86    }
 87  }
 88  if ((millis() - prevTime_A) > waitTime_A) {
 89    if (currRead_A != currState_A) {
 90      currState_A = currRead_A;
 91      if (currState_A == LOW) {
 92        // Send the code
 93        buf[2] = 4;   // HID: A key
 94#ifdef SERIAL_DEBUG
 95        buf[2] = 'A';   // Serial: A key
 96#endif
 97        Serial.write(buf, 8); // Send keypress
 98      } else {
 99        // Release the keyboard
100        releaseKey();
101      }
102    }
103  }
104  if ((millis() - prevTime_S) > waitTime_S) {
105    if (currRead_S != currState_S) {
106      currState_S = currRead_S;
107      if (currState_S == LOW) {
108        // Send the code
109        buf[2] = 22;    // HID: S key
110#ifdef SERIAL_DEBUG
111        buf[2] = 'S';     // Serial: S key
112#endif
113        Serial.write(buf, 8); // Send keypress
114      } else {
115        // Release the keyboard
116        releaseKey();
117      }
118    }
119  }
120  if ((millis() - prevTime_D) > waitTime_D) {
121    if (currRead_D != currState_D) {
122      currState_D = currRead_D;
123      if (currState_D == LOW) {
124        // Send the code
125        buf[2] = 7;   // HID: D key
126#ifdef SERIAL_DEBUG        
127        buf[2] = 'D';   // Serial: D key
128#endif
129        Serial.write(buf, 8); // Send keypress
130      } else {
131        // Release the keyboard
132        releaseKey();
133      }
134    }
135  }
136
137  prevState_W = currRead_W;
138  prevState_A = currRead_A;
139  prevState_S = currRead_S;
140  prevState_D = currRead_D;
141
142}
143
144void releaseKey() 
145{
146  buf[0] = 0;
147  buf[2] = 0;
148  Serial.write(buf, 8); // Release key  
149}