====== TGP communication protocol ======

===== Data model =====

  * project consists of multiple pages
  * each page contains a list of objects
  * each object may have one or more associated parameters
  * a parameter can be of type: bit, nibble, byte, integer, or long

  * sending page command displays the page with objects and their values
  * changing an object sends event with parameter index and new value

===== Message frame =====

  * uart parameters: 115200 8n1
  * integers are little endian (low byte first)

^ A0h  ^ device  ^ page  ^ pp0_lo  ^ pp0_hi  ^ pp1_lo  ^ pp1_hi  ^ pp2_lo  ^ pp2_hi  ^ checksum  ^
|  0   |  1      |  2    |  3      |  4      |  5      |  6      |  7      |  8      |  9        |

  * A0h - page frame, cybro-to-display
  * device - device receiving the message (00h-broadcast, 01h..FFh-device number)
  * page - request to display specified page
  * pp0..pp2 - parameters (optional)
  * checksum - sum of all bytes before the checksum mod 256

^ A1h  ^ device  ^ event  ^ ep0_lo  ^ ep0_hi  ^ ep1_lo  ^ ep1_hi  ^ ep2_lo  ^ ep2_hi  ^ checksum  ^
|  0   |  1      |  2     |  3      |  4      |  5      |  6      |  7      |  8      |  9        |

  * A1h - event frame, display-to-cybro
  * device - device sending the message (00h-not defined, 01h..FFh-device number)
  * event - event triggered by user
  * ep0..ep2 - parameters (optional)
  * checksum - sum of all bytes before the checksum mod 256


===== Parameter encoding=====

|<500px 100px >|
^ 1x long  | long0 = pp0 + pp1<<16                                                                                     |
^ 3x int   | int0 = pp0, \\ int1 = pp1, \\ int2 = pp2                                                                  |
^ 6x byte  | byte0 = pp0lo, \\ byte1 = pp0hi, \\ byte2 = pp1lo, \\ byte3 = pp1hi, \\ byte4 = pp2lo, \\ byte5 = pp2hi   |
^ 12x nib  | nib0 = pp0n0, \\ nib1 = pp0n1, \\ nib2 = pp0n2, \\ nib3 = pp0n3, \\ nib4 = pp1n0, \\ nib5 = pp1n1,\\ ...  |
^ 48x bit  | bit0 = pp0b0, \\ bit1 = pp0b1, \\ bit2 = pp0b2, \\ bit3 = pp0b3, \\ bit4 = pp0b4, \\ bit5 = pp0b5,\\ ...  |

Any combination of types can be used.

===== Object specifications =====

|                        ^  page          ^  event                                        ^
^ decimal number         | enable, value  | none                                          |
^ multi-state indicator  | enable, value  | none                                          |
^ push button            | enable         | 1 = press, \\ 2 = release, \\ 3 = long press  |
^ toggle button          | enable, value  | value                                         |
^ slider input           | enable, value  | value (on change, max 200ms)                  |
^ numeric input          | enable, value  | value (update on enter)                       |

===== Cybro-to-Display =====

^  page  ^  pp0              ^  pp1              ^  pp2  ^  description                                         ^
^  0     |  0                |  0                |  0    | none                                                 |
^  1     |  0                |  0                |  0    | ping, used to check the connection                   |
^  2     |  parameter index  |  parameter value  |  0    | generic write when the page has too many parameters  |
^  10+   |                   |                   |       | project-specific pages                               |


===== Display-to-Cybro =====

^  event       ^  ep0           ^  ep1           ^  ep2  ^  description                        ^
^  0           |  0             |  0             |  0    | none                                |
^  1           |  0             |  0             |  0    | ping, used to check the connection  |
^  2           |  page          |  0             |  0    | page request                        |
^  10+\\ page  |  object index  |  object value  |  0    | object change                       |


===== Example =====

|  A0  |  00  |  page=22  |  pp0=220 (setpoint)  |  pp1=-1 (disable)  |  pp2=-1 (disable)  |

=> set page 22, setpoint 22.0°C, disable fan, disable ventilator

|  A1  |  00  |  page=22  |  ep0=0 (setpoint)  |  ep1=225 (value)  |

=> setpoint changed to 22.5°C