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Protocol.md

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UARTSwitchCon protocol.

(and to an extent, SwitchInputEmulator protocol)

Baud: 19200

Handshake:

Vanilla:

Goes into Chocolate mode... (I'm gonna need to rename this...)

Will simplify inputs according to the following comments.

  // Initial, vanilla handshake.
  // MASTER: 0xFF
  // SLAVE: 0xFF
  // MASTER: 0x33
  // SLAVE: 0xCC
  // MASTER: 0xCC
  // SLAVE: 0x33, then 0x90 with each packet sent as an HID
  
        // So... This is a big fork in the road between the original
        // SwitchInputEmulator and mine here on the ESP32.

        // Normally, it would just send the values as is, but now with the
        // original handshake (Master: FF 33 CC), it will go into what I am
        // naming "Chocolate" mode. Where inputs are simplified and
        // converted for sideways joycons (if it is set as a Joy-Con, that
        // is.)

        // DPad, Left Stick, and Right Stick is all converted to the main
        // stick for that controller. (Left stick for L Joy-Con and Pro Con,
        // Right stick for R Joy-Con).
        // As of writing, the order of importance is:
        // DPad, L Stick, R Stick. If one of those is off center, the first
        // one in that list is the one the stick is set off of.

        // A B X Y is set to the proper side for the sideways joycon.
        // Example: A is going to be Down on L JC, and X on R JC.

        // Shoulder buttons are simplified in this way:
        // Sending either L, ZL, or SL, will press:
        // L, ZL on Pro Con
        // SL on Joy-Cons.
        // Similar behavior is on the right side as well.

Chocolate:

  // "Chocolate" handshake.
  // MASTER: 0xFF
  // SLAVE: 0xFF
  // MASTER: 0x44
  // SLAVE: 0xEE
  // MASTER: 0xEE
  // SLAVE: CONTROLLER_TYPE, then 0x90 with each packet sent as an HID

Goes into original mode.

Inputs are sent exactly as sent.

Packets

Byte 0 1 2 3 4 5 6 7 8
Data MSB Buttons LSB Buttons HAT/DPad LX LY RX RY Vendor Spec (unused?) CRC8

Byte 0:

Bit 0 1 2 3 4 5 6 7
Button Y B A X L R ZL ZR

Byte 1:

Bit 0 1 2 3 4 5 6 7
Button Minus Plus L Clk R Clk Home Capture SL SR

Byte 2:

A_DPAD_CENTER    = 0x08
A_DPAD_U         = 0x00
A_DPAD_U_R       = 0x01
A_DPAD_R         = 0x02
A_DPAD_D_R       = 0x03
A_DPAD_D         = 0x04
A_DPAD_D_L       = 0x05
A_DPAD_L         = 0x06
A_DPAD_U_L       = 0x07

Also can be visualized with:

-- TOP --
7 0 1
6 8 2
5 4 3

Byte 8:

CRC8 is calculated with this:

// https://www.microchip.com/webdoc/AVRLibcReferenceManual/group__util__crc_1gab27eaaef6d7fd096bd7d57bf3f9ba083.html
uint8_t crc8_ccitt_update(uint8_t inCrc, uint8_t inData) {
  uint8_t i;
  uint8_t data;

  data = inCrc ^ inData;

  for (i = 0; i < 8; i++) {
    if ((data & 0x80) != 0) {
      data <<= 1;
      data ^= 0x07;
    } else {
      data <<= 1;
    }
  }
  return data;
}