Add Virtual-On mode

Implement Virtual-On mode that emulates the twin stick controller
by single arcade controller that has only one 1 stick and 4 buttons.

The arcade stick affects both left and right sticks, but if button 2
is pressed, right results in turning left, left does turning right,
up does jumping, and down does cancelling it. Button 1 is L shot,
button 4 is R shot, and button 3 is turbo for both L and R.

Not sure if this is the best assignments, but it works enough.
Suggestion is welcomed, but definitely using SS twin stick is the
best alternative way to play Virtual-On.

iona.ino

@@ -8,32 +8,35 @@ JVSIO io;
 
 // Some NAOMI games expects the first segment starts with "SEGA ENTERPRISES,LTD.".
 // E.g. one major official I/O board is "SEGA ENTERPRISES,LTD.;I/O 838-13683B;Ver1.07;99/16".
-static const char io_id[] = "SEGA ENTERPRISES,LTD.compat;IONA-NANO;ver0.93;Normal Mode";
-static const char suchipai_id[] = "SEGA ENTERPRISES,LTD.compat;IONA-NANO;Ver0.93;Su Chi Pai Mode";
+static const char io_id[] = "SEGA ENTERPRISES,LTD.compat;IONA-NANO;ver0.94;Normal Mode";
+static const char suchipai_id[] = "SEGA ENTERPRISES,LTD.compat;IONA-NANO;Ver0.94;Su Chi Pai Mode";
+static const char virtualon_id[] = "SEGA ENTERPRISES,LTD.compat;IONA-NANO;Ver0.94;Virtual-On Mode";
 uint8_t ios[5] = { 0x00, 0x00, 0x00, 0x00, 0x00 };
 uint8_t coinCount = 0;
 uint8_t mode = 0;
 uint8_t coin = 0;
 uint8_t gpout = 0;
 
 bool suchipai_mode = false;
+bool virtualon_mode = false;
 
 int in(int pin, int shift) {
   return (digitalRead(pin) ? 0 : 1) << shift;
 }
 
 void updateMode() {
   int value = analogRead(A7);
-  if (value < 170)
+  if (value < 170)       // SW1-OFF, SW2-OFF
     mode = 0;
-  else if (value < 420)
+  else if (value < 420)  // SW1-OFF, SW2-ON
     mode = 1;
-  else if (value < 570)
+  else if (value < 570)  // SW1-ON , SW2-OFF
     mode = 2;
   else
     mode = 3;
 
   suchipai_mode = mode == 2;
+  virtualon_mode = mode == 1;
 }
 
 uint8_t suchipaiReport() {
@@ -69,6 +72,52 @@ uint8_t suchipaiReport() {
   return start;
 }
 
+uint8_t virtualonReport(size_t player, size_t line) {
+  //       |  B7 |  B6 |  B5 |  B4 |  B3 |  B2 |  B1 |  B0 |
+  // ------+-----+-----+-----+-----+-----+-----+-----+-----+
+  // P0-L1 |Start|  -  | L U | L D | L L | L R |L sht|L trb|
+  // P0-L2 | QM  |  -  |  -  |  -  |  -  |  -  |  -  |  -  |
+  // P1-L1 |  -  |  -  | R U | R D | R L | R R |R sht|R trb|
+  // P1-L2 |  -  |  -  |  -  |  -  |  -  |  -  |  -  |  -  |
+
+  // Try fullfilling 2 stick controlls avobe via usual single
+  // arcade controller that has only 1 stick and 4 buttons.
+  // Button 1 - L shot
+  // Button 2 - turn or jump w/ stick
+  // Button 3 - LR turbo
+  // Button 4 - R shot
+  if (player >= 2 || line != 1)
+    return 0x00;
+  uint8_t data = 0x00;
+  bool rotate = ios[1] & 1;
+  if (rotate) {
+    bool up = ios[1] & 32;
+    bool down = ios[1] & 16;
+    bool left = ios[1] & 8;
+    bool right = ios[1] & 4;
+    if (player == 0) { // Left Stick
+      if (left) data |= 32;
+      if (right) data |= 16;
+      if (up) data |= 8;
+      if (down) data |= 4;
+    } else {  // Right Stick
+      if (left) data |= 16;
+      if (right) data |= 32;
+      if (up) data |= 4;
+      if (down) data |= 8;
+    }
+  } else {
+    data = ios[1] & ~3;
+  }
+  if (player == 0 && ios[1] & 2)
+    data |= 2;
+  if (player == 1 && ios[2] & 64)
+    data |= 2;
+  if (ios[2] & 128)
+    data |= 1;
+  return data;
+}
+
 void setup() {
   io.begin();
 
@@ -102,7 +151,7 @@ void loop() {
    case JVSIO::kCmdIoId:
     io.pushReport(JVSIO::kReportOk);
     {
-      const char* id = suchipai_mode ? suchipai_id : io_id;
+      const char* id = virtualon_mode ? virtualon_id : suchipai_mode ? suchipai_id : io_id;
       for (size_t i = 0; id[i]; ++i)
         io.pushReport(id[i]);
     }
@@ -141,7 +190,9 @@ void loop() {
     io.pushReport(ios[0]);
     for (size_t player = 0; player < data[1]; ++player) {
       for (size_t line = 1; line <= data[2]; ++line) {
-        if (player)
+        if (virtualon_mode)
+          io.pushReport(virtualonReport(player, line));
+        else if (player)
           io.pushReport(0x00);
         else if (suchipai_mode)
           io.pushReport(suchipaiReport());