Add parallel port comms to arduino

arduino/kbd/kbd.cc

@@ -0,0 +1,193 @@
+// keyboard wiring diagram:
+// https://www.minuszerodegrees.net/5150/misc/5150_keyboard_reset.jpg
+
+#include "Arduino.h"
+
+constexpr int kClockPin = PC6;
+constexpr int kDataPin = PC4;
+
+constexpr int kBitDelayMicros = 100;
+constexpr int kCodeDelayMicros = 200;
+constexpr int kKeyDelayMicros = 100;
+
+namespace {
+
+void sendCode(int code) {
+    // preconditions: clock and data pins are INPUT
+
+    while (digitalRead(kDataPin) == LOW || digitalRead(kClockPin) == LOW) {
+        // wait. we're not allowed to send
+    }
+
+    digitalWrite(kDataPin, LOW);
+    digitalWrite(kClockPin, LOW);
+
+    pinMode(kClockPin, OUTPUT);
+    delayMicroseconds(kBitDelayMicros);
+    pinMode(kClockPin, INPUT);
+    // delayMicroseconds(kDelayMicros);
+
+    for (int i = 0; i < 8; i++) {
+        if ((code & (1 << i)) == 0) {
+            // send a 0
+            pinMode(kDataPin, OUTPUT);
+        } // else do nothing, it's already a 1
+        delayMicroseconds(kBitDelayMicros);
+
+        pinMode(kClockPin, OUTPUT);
+        delayMicroseconds(kBitDelayMicros);
+        pinMode(kDataPin, INPUT);
+        pinMode(kClockPin, INPUT);
+    }
+    delayMicroseconds(kCodeDelayMicros);
+}
+
+enum State {
+    kReady,
+    kMaybeReset,
+};
+
+constexpr int kResetDelay = 19;
+
+constexpr int kLetterCodes[] = {
+        0x1E, // 'a'
+        0x30, 0x2E, 0x20, 0x12, 0x21, 0x22, 0x23, 0x17, 0x24,
+        0x25, 0x26, 0x32, 0x31, 0x18, 0x19, 0x10, 0x13, 0x1F,
+        0x14, 0x16, 0x2F, 0x11, 0x2D, 0x15, 0x2c,
+};
+
+constexpr int kNumberCodes[] = {
+        0x0B, // '0'
+        0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A,
+};
+
+void sendNormalCode(int code) {
+    sendCode(code);
+    sendCode(code | 0x80);
+}
+
+void sendShiftCode(int code) {
+    sendCode(42); // left shift
+    sendNormalCode(code);
+    sendCode(42 | 0x80);
+}
+
+void sendCtrlAltDel() {
+    sendCode(0x1d); // ctrl
+    sendCode(0x38); // alt
+    sendCode(0x53); // del
+    sendCode(0x53 | 0x80);
+    sendCode(0x38 | 0x80);
+    sendCode(0x1d | 0x80);
+}
+
+void sendCtrlBreak() {
+    sendCode(0x1d); // ctrl
+    sendCode(0x46); // break
+    sendCode(0x46 | 0x80);
+    sendCode(0x1d | 0x80);
+}
+
+} // namespace
+
+void sendAsciiChar(int c) {
+    if (c >= 'a' && c <= 'z') {
+        return sendNormalCode(kLetterCodes[c - 'a']);
+    } else if (c >= '0' && c <= '9') {
+        return sendNormalCode(kNumberCodes[c - '0']);
+    } else if (c >= 'A' && c <= 'Z') {
+        return sendShiftCode(kLetterCodes[c - 'A']);
+    }
+    switch (c) {
+    case '-':
+        return sendNormalCode(12);
+    case '=':
+        return sendNormalCode(13);
+    case '[':
+        return sendNormalCode(26);
+    case ']':
+        return sendNormalCode(27);
+    case ';':
+        return sendNormalCode(39);
+    case '\'':
+        return sendNormalCode(40);
+    case ',':
+        return sendNormalCode(51);
+    case '.':
+        return sendNormalCode(52);
+    case '/':
+        return sendNormalCode(53);
+    case ' ':
+        return sendNormalCode(57);
+    case '\n':
+        return sendNormalCode(28);
+
+    case '!':
+        return sendShiftCode(2);
+    case '@':
+        return sendShiftCode(3);
+    case '#':
+        return sendShiftCode(4);
+    case '$':
+        return sendShiftCode(5);
+    case '%':
+        return sendShiftCode(6);
+    case '^':
+        return sendShiftCode(7);
+    case '&':
+        return sendShiftCode(8);
+    case '*':
+        return sendShiftCode(9);
+    case '(':
+        return sendShiftCode(10);
+    case ')':
+        return sendShiftCode(11);
+    case '_':
+        return sendShiftCode(12);
+    case '+':
+        return sendShiftCode(13);
+
+    case '{':
+        return sendShiftCode(26);
+    case '}':
+        return sendShiftCode(27);
+    case ':':
+        return sendShiftCode(39);
+    case '"':
+        return sendShiftCode(40);
+    case '<':
+        return sendShiftCode(51);
+    case '>':
+        return sendShiftCode(52);
+    case '?':
+        return sendShiftCode(53);
+
+    case 0:
+        return sendCtrlAltDel();
+    case 27:
+        return sendCtrlBreak(); // escape
+    }
+}
+
+void setupKbd() {
+    pinMode(kClockPin, INPUT);
+    pinMode(kDataPin, INPUT);
+}
+
+void checkKbdReset() {
+    static State state = kReady;
+    static int lastclocklow = 0;
+
+    int clockp = digitalRead(kClockPin);
+    if (state == State::kReady && clockp == LOW) {
+        state = State::kMaybeReset;
+        lastclocklow = millis();
+    } else if (state == State::kMaybeReset) {
+        if (clockp == HIGH && millis() - lastclocklow > kResetDelay) {
+            delay(1);
+            state = State::kReady;
+            sendCode(0xaa);
+            Serial.println("Reset!");
+        }
+    }
+}