Sunday, November 13, 2011

Arduino PS2 Emulator-Computer Control!

I wanted to control my computer with a Arduino and sonar module, but wasn't exactly sure how to connect the computer and Arduino. I could either send data via serial and have a C# program interpret the data and emulate a key press accordingly, or I found a way for the Arduino to act as a PS2 keyboard. Once i learn more about C# I may redo it, but using the PS2 emulator is the far easier option. The program is pretty similar to the TV sonar control program except it sends PS2 commands for tabbing, volume, copy and paste. To connect it to the computer i just have to connect the two digital pins specified in the code to the appropriate pins in a PS2 connector and plug it in to my computer. The Arduino sends keys using "scan codes"; these are universal to any PS2 keyboard, so it could probably work on a Mac. More after the break.



Scan codes can be found here. At first they were confusing, but there was a well worded example on the website on how to use them:

"What sequence of make codes and break codes should be sent to your computer for the character "G" to appear in a word processor? Since this is an upper-case letter, the sequence of events that need to take place are: press the "Shift" key, press the "G" key, release the "G" key, release the "Shift" key. The scan codes associated with these events are the following: make code for the "Shift" key (12h), make code for the "G" key (34h), break code for the "G" key(F0h,34h), break code for the "Shift" key (F0h,12h). Therefore, the data sent to your computer would be: 12h, 34h, F0h, 34h, F0h, 12h."

In Arduino code it would be:
keyboard.write(0x12);
keyboard.write(0x34);
keyboard.write(0xF0);
keyboard.write(0x34);
keyboard.write(0xF0);
keyboard.write(0x12);

Code:
//KBD stuff
#include "ps2dev.h"  // to emulate a PS/2 device
PS2dev keyboard(3,2);  // PS2dev object (2:data, 3:clock)
int enabled = 0;  // pseudo variable for state of "keyboard"
unsigned char c;  //char stores data recieved from computer for KBD

//Sonar stuff
const int numReadings = 5;   // set a variable for the number of readings to take
int index = 0;                // the index of the current reading
int total = 0;                // the total of all readings
int average = 0;              // the average
int oldAverage = 0;           // the old average
int echoPin = 6;              // the SRF05's echo pin
int trigPin = 7;              // the SRF05's init pin
unsigned long pulseTime = 0;  // variable for reading the pulse
unsigned long distance = 0;   // variable for storing distance

void ack()
{
  //acknowledge commands
  while(keyboard.write(0xFA));
}

int keyboardcommand(int command)
{
  unsigned char val;
  switch (command)
  {
  case 0xFF: //reset
    ack();
    //the while loop lets us wait for the host to be ready
    while(keyboard.write(0xAA)!=0);
    break;
  case 0xFE: //resend
    ack();
    break;
  case 0xF6: //set defaults
    //enter stream mode
    ack();
    break;
  case 0xF5: //disable data reporting
    //FM
    enabled = 0;
    ack();
    break;
  case 0xF4: //enable data reporting
    //FM
    enabled = 1;
    ack();
    break;
  case 0xF3: //set typematic rate
    ack();
    keyboard.read(&val); //do nothing with the rate
    ack();
    break;
  case 0xF2: //get device id
    ack();
    keyboard.write(0xAB);
    keyboard.write(0x83);
    break;
  case 0xF0: //set scan code set
    ack();
    keyboard.read(&val); //do nothing with the rate
    ack();
    break;
  case 0xEE: //echo
    //ack();
    keyboard.write(0xEE);
    break;
  case 0xED: //set/reset LEDs
    ack();
    keyboard.read(&val); //do nothing with the rate
    ack();
    break;
  }
}

void setup()
{
  // send the keyboard start up
  while(keyboard.write(0xAA)!=0);
  delay(10);
  // make the init pin an output:
  pinMode(trigPin, OUTPUT);
  // make the echo pin an input:
  pinMode(echoPin, INPUT);
  // initialize the serial port:
  Serial.begin(9600);
}

void loop()
{
  // loop for a number of readings on the SRF-05 to get an average to smooth the results. Much like all my other examples
  for (index = 0; index<=numReadings;index++)
  {
    digitalWrite(trigPin, HIGH);
    delay(1);
    digitalWrite(trigPin, LOW);
    pulseTime = pulseIn(echoPin, HIGH);
    distance = pulseTime/58;
    total = total + distance;
    delay(5);
  }
  // store the previous reading
  oldAverage = average;
  // store the current reading
  average = total/numReadings;
  // debug to check for spikes in the sensor etc..
  Serial.println(average);

  //if host device wants to send a command:
  if( (digitalRead(3)==LOW) || (digitalRead(2) == LOW))
  {
    while(keyboard.read(&c)) ;
    keyboardcommand(c);
  }
  else
  {
    // now the fun part...
    // if my distance is less than 5...
    if (average <=5)
    {
      int x = 0;
      if(x<=5)  //how many times to press tab
      {
        Serial.println("TAB+ALT");
        keyboard.write(0x11); //send ALT
        keyboard.write(0x0D); //then send Tab

        keyboard.write(0xF0);  //tab break
        keyboard.write(0x0D);  //...
        delay(700); // wait so doesnt tab too fast

        if(x<=5)
        {
          keyboard.write(0x0D); //send another Tab
          keyboard.write(0xF0);  //tab break
          keyboard.write(0x0D);  //...        
          delay(700);
        }
      }
      else //x is nolonger <=5 must be 6, set x to 0, and end all keys
      {
        x=0; //reset tab counter
        keyboard.write(0xF0);  //tab break
        keyboard.write(0x0D);  //...

        keyboard.write(0xF0);  //alt break
        keyboard.write(0x11);  //...

      }
      x++; //add 1 to tab counter
    }
    else // otherwise if my hand is higher
    {
      // check to see if my hand is in the registered space above the sensor
      if (average <=20 && average >=10 && oldAverage >=10)
      {
        // the below statement is our sensitive the readings are so if the current and previous readings are different with a tolerance of +/
        //we can look at the direction of movement
        if ((average != oldAverage) && (average+1 != oldAverage) && (average-1 != oldAverage))
        {
          // if the current reading is higher than the previous, then my hand is moving upwards
          if (average > oldAverage)
          {
            Serial.println("Sound up");
            keyboard.write(0xE0); //make volume +
            keyboard.write(0x32); //...
            keyboard.write(0xE0); //break
            keyboard.write(0xF0); //...
            keyboard.write(0x32); //...
            delay(150);  //wait so it doesnt change volume rapidly
          }
          else
          {
            // otherwise if it is below then my hand is moving downwards
            if (average < oldAverage && oldAverage <=20)
            {
              Serial.println("Sound down");
              keyboard.write(0xE0); //make volume -
              keyboard.write(0x21); //...
              keyboard.write(0xE0); //break
              keyboard.write(0xF0); //...
              keyboard.write(0x21); //...
              delay(150);
            }
          }
          // otherwise my hand must be stationary so check where it is.
        }
        else
        {
          // if my hand is stationary between 10 and 15 cms away from the sensor
          if (average >= 10 && average <=15)
          {
            Serial.println("Copy");
            keyboard.write(0x14); //make CNTRL
            keyboard.write(0x21); //make 'c'

            keyboard.write(0xF0); //break 'c' break
            keyboard.write(0x21); //...
            keyboard.write(0xF0); //break FO capital o) CNTRL break
            keyboard.write(0x14); //...
            delay(250);
          }
          else
          {
            // if my hand is a bit higher up...
            if (average >= 16 && average <=20)
            {
              Serial.println("Paste");
              keyboard.write(0x14); //make CNTRL
              keyboard.write(0x2A); //make 'v'

              keyboard.write(0xF0); //break 'v' break
              keyboard.write(0x2A); //...
              keyboard.write(0xF0); //break FO capital o) CNTRL break
              keyboard.write(0x14); //...
              delay(250);
            }
          }
        }
      }
    }
  }
  // clear our index and total for the next reading just in case
  if (index >= numReadings)
  {
    index = 0;
    total = 0;
  }
}

5 comments:

  1. Nice work. I've successfully prototyped a PS2 keyboard using this library after reading your article. Thank you for the line by line explanation. :)

    But it's not clear to me why you used pin 2 and 3. Does it have anything to do with the interrupt?

    ReplyDelete
    Replies
    1. any pins can be used as set in the line:

      PS2dev keyboard(3,2); // PS2dev object (2:data, 3:clock)

      Delete
  2. It's intresting for me. But were can i find the "ps2dev.h". Thank you!

    ReplyDelete
  3. I tried it but it can send char to computer

    ReplyDelete