{"id":683,"date":"2013-09-11T11:13:05","date_gmt":"2013-09-11T15:13:05","guid":{"rendered":"http:\/\/www.logicalzero.com\/blog\/?p=683"},"modified":"2014-08-08T21:35:10","modified_gmt":"2014-08-09T01:35:10","slug":"check-out-my-atari-key-pad-part-3-making-it-work","status":"publish","type":"post","link":"http:\/\/www.logicalzero.com\/blog\/?p=683","title":{"rendered":"Check Out my (Atari Key-)Pad, Part 3: Making it Work"},"content":{"rendered":"

\"Keypad<\/a>Note:<\/strong> for some reason, something in the combination of the code listings in this post, the syntax highlighter I’m using (Crayon), and my theme causes rendering problems in some browsers. I apologize if parts are difficult to read. I’m looking into it.<\/em><\/p>\n

To recap: In part 1<\/a>, I figured out how the CX85 keypad works and how it’s wired; in part 2<\/a>, I made a change to the Arduino’s HID library that will give me more control over the keypad emulation. Now, to write a sketch to drive it!<\/p>\n

Hooking the keypad up to an Arduino Leonardo was trivially easy. I used a male DB9 on a ribbon cable, the serial port from an old computer. A simple breakout board (the most complex part of the setup) just widens the 2×5 header connector enough to fit across the gap of a breadboard, DIP style. I wired it to the Arduino somewhat out of order:
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<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
DB9 Pin<\/th>\nName<\/th>\nArduino Pin<\/th>\n<\/tr>\n
1<\/td>\nOUTA<\/code><\/td>\n3<\/td>\n<\/tr>\n
2<\/td>\nOUTB<\/code><\/td>\n6<\/td>\n<\/tr>\n
3<\/td>\nOUTC<\/code><\/td>\n4<\/td>\n<\/tr>\n
4<\/td>\nOUTD<\/code><\/td>\n7<\/td>\n<\/tr>\n
5<\/td>\nOUTE<\/code><\/td>\n5<\/td>\n<\/tr>\n
6<\/td>\nDATA_AV<\/code><\/td>\n2<\/td>\n<\/tr>\n
7<\/td>\nVCC<\/code><\/td>\n+5V<\/td>\n<\/tr>\n
8<\/td>\nGND<\/code><\/td>\nGND<\/td>\n<\/tr>\n
9<\/td>\n(No connection)<\/em><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

<\/center><\/p>\n

This order was simply the tidiest layout on my little breadboard; I didn’t bother getting the OUT*<\/code> pins in sequence. The only critical pin is DATA_AV<\/code>, attached to Arduino pin 2; an interrupt handler listening to changes on that pin does all the work. It’s worth mentioning that pins 3-5 are all part of the same port<\/a> on an Arduino Uno (specifically, PORTD<\/code>), which I used for my initial experiments. The Leonardo uses a different microcontroller with a weirder layout of ports, so I’m just reading the inputs with old digitalRead()<\/code>, but the consecutive pins are still useful for iterating.<\/p>\n

The Arduino sketch itself is moderately simple. As I mentioned earlier, it uses an interrupt handler (handleKeypress()<\/code>)attached to pin 2 to actually handles the key presses on the keypad and send the corresponding USB keyboard scan codes. Note that the values sent as the first argument to sendKey()<\/code> are the codes that the keyboard uses to represent the keys, not the characters.<\/p>\n

\/*\r\n Atari CX85 Keypad to USB\r\n David Stokes, 2013\r\n http:\/\/www.logicalzero.com\/blog\/?cat=59\r\n*\/\r\n\r\n\/\/ The keypad's output for each of its keys\r\nconst byte KEYPAD_DEL =       B00100;\r\nconst byte KEYPAD_YES =       B00101;\r\nconst byte KEYPAD_5 =         B00110;\r\nconst byte KEYPAD_2 =         B00111;\r\nconst byte KEYPAD_ESC =       B01001;\r\nconst byte KEYPAD_NO =        B01100;\r\nconst byte KEYPAD_0 =         B01101;\r\nconst byte KEYPAD_8 =         B01110;\r\nconst byte KEYPAD_PLUSENTER = B01111;\r\nconst byte KEYPAD_4 =         B10100;\r\nconst byte KEYPAD_1 =         B10101;\r\nconst byte KEYPAD_6 =         B10110;\r\nconst byte KEYPAD_3 =         B10111;\r\nconst byte KEYPAD_7 =         B11100;\r\nconst byte KEYPAD_DOT =       B11101;\r\nconst byte KEYPAD_9 =         B11110;\r\nconst byte KEYPAD_MINUS =     B11111;\r\n\r\nstatic byte key;\r\n\r\nvoid handleKeypress() {\r\n  boolean d = digitalRead(2);\r\n\r\n  \/\/ Emergency escape. If pin 13 is LOW, output is inhibited.\r\n  if (!digitalRead(13))\r\n    return;\r\n\r\n  if (!d) {\r\n    \/\/ Pressed! \r\n    \/\/ Read the key pressed.\r\n    key = 0;\r\n    for (byte i=3; i<8; i++)\r\n      key = (key << 1) | digitalRead(i);\r\n\r\n    switch (key) {\r\n      \/\/ Standard keys: map directly to modern keys\r\n    case KEYPAD_MINUS:\r\n      sendKey(0x56, 0);\r\n      break;\r\n    case KEYPAD_PLUSENTER:\r\n      \/\/ The keypad \"Plus\" key is 0x57, \"Enter\" key is 0x58\r\n      \/\/ Enter is probably more useful.\r\n      sendKey(0x58, 0);\r\n      break;\r\n    case KEYPAD_1:\r\n      sendKey(0x59, 0);\r\n      break;\r\n    case KEYPAD_2:\r\n      sendKey(0x5A, 0);\r\n      break;\r\n    case KEYPAD_3:\r\n      sendKey(0x5B, 0);\r\n      break;\r\n    case KEYPAD_4:\r\n      sendKey(0x5C, 0);\r\n      break;\r\n    case KEYPAD_5:\r\n      sendKey(0x5D, 0);\r\n      break;\r\n    case KEYPAD_6:\r\n      sendKey(0x5E, 0);\r\n      break;\r\n    case KEYPAD_7:\r\n      sendKey(0x5F, 0);\r\n      break;\r\n    case KEYPAD_8:\r\n      sendKey(0x60, 0);\r\n      break;\r\n    case KEYPAD_9:\r\n      sendKey(0x61, 0);\r\n      break;\r\n    case KEYPAD_0:\r\n      sendKey(0x62, 0);\r\n      break;\r\n    case KEYPAD_DOT:\r\n      sendKey(0x63, 0);\r\n      break;\r\n\r\n    \/\/ Non-standard keys, arbitrarily mapped.\r\n    case KEYPAD_DEL:\r\n      \/\/ Send \"Del\" (from the cluster above the arrow keys)\r\n      sendKey(0x4C, 0);\r\n      break;\r\n    case KEYPAD_YES:\r\n      \/\/ Send multimedia keyboard \"Volume Up\"\r\n      sendKey(0x80, 0);\r\n      break;\r\n    case KEYPAD_NO:\r\n      \/\/ Send multimedia keyboard \"Volume Down\"\r\n      sendKey(0x81, 0);\r\n      break;\r\n    case KEYPAD_ESC:\r\n      \/\/ Sends \"Play\/Pause\" key (semi-standard)\r\n      \/\/ BUG: This doesn't actually work; this seem to be 'special' and may \r\n      \/\/ involve multiple bytes.\r\n      sendKey(0xE8, 0);\r\n      break;\r\n    }\r\n  }\r\n  else {\r\n    \/\/ Key released. If the user has pressed more than one key, the keypad\r\n    \/\/ only reports the ID of the last one, so releaseKeys() releases all\r\n    \/\/ keys, not just the one identified by OUT*. \r\n    releaseKeys();\r\n  }\r\n  key = 0;  \r\n}\r\n\r\n\r\nvoid setup(){\r\n  \/\/ The keypad's DATA_AV and OUT* should be attached to pins 2-7.\r\n  for (byte i=2; i<8; i++)\r\n    pinMode(i, INPUT);\r\n\r\n  \/\/ Pin 13 is used as a safety mechanism. If LOW, keypad output is disabled,\r\n  \/\/ just in case a bug causes the Arduino to freak out. This can be safely \r\n  \/\/ removed later.\r\n  pinMode(13, INPUT_PULLUP);\r\n\r\n  \/\/ Keypad's DATA_AV is on pin 2, which corresponds to interrupt 1 on the \r\n  \/\/ Arduino Leonardo.\r\n  attachInterrupt(1, handleKeypress, CHANGE);\r\n}\r\n\r\nvoid loop() {\r\n  \/\/ This space intentionally left blank; the interrupt handler does all \r\n  \/\/ the real work.\r\n}\r\n\r\n\/\/ sendKey() was largely borrowed from:\r\n\/\/ https:\/\/github.com\/una1veritas\/Arduino\/tree\/master\/HID_Keyboard_Advanced\r\nvoid sendKey(byte key, byte modifiers)\r\n{\r\n  KeyReport report = { 0 };  \/\/ Create an empty KeyReport\r\n  report.keys[0] = key;  \/\/ set the KeyReport to key\r\n  report.modifiers = modifiers;  \/\/ set the KeyReport's modifiers\r\n  report.reserved = 1;\r\n  Keyboard.sendReport(&report);  \/\/ send the KeyReport\r\n}\r\n\r\n\/\/ releaseKeys() was separated from sendKey() so that things like auto-repeat\r\n\/\/ still work. \r\nvoid releaseKeys() {\r\n  KeyReport report = { 0 };  \/\/ Create an empty KeyReport\r\n  report.reserved = 0;\r\n  Keyboard.sendReport(&report);  \/\/ send the empty key report\r\n}\r\n<\/pre>\n
What’s next? On the hardware side:<\/p>\n