Drivers/Braille/LogText/PROTOCOL

File: Develop
by Hans Schou

Logtext manufactor:
 Tactilog
 Roskildevej 15
 DK-7441 Bording

 Contact: Poul Erik Skov
 Phone: +45 86 86 20 88
 Fax: +45 86 86 21 88

9600 baud

Logtext protocol
----------------

1. Request from Logtext

1.1. Update a line: <start><line>
 start: start code 0xFF
 
 line: line number to update
   0x01 <= line 0x19
when going into terminal

1.2. Update cursor line: <start><0>
 start: start code 0xFF

 0: code 0x00

2. Answer from computer

2.1. Protocol: <start><line><cursor><column><count><text>
 start: start code 0xFF.

 line: line number on screen.
   0x01 <= line 0x19

 cursor: cursor position on this line.
   0x01 <= cursor <= 0x50
 Special cursor == 0x00, no cursor on this line.

 column: text starts from this column.
   0x01 <= column <= 0x50

 count: number of bytes in text.
   0x00 <= count <= 0x50

 text: ASCII characters. Any character except 0xFF.
  It is not possible to turn on all dots (0xFF).


2.2. Automatic cursor tracking.
If the mode is currently in cursor tracking and the
cursor moves to another line, the computer should send
a new updated line to Logtext. If the cursor moves
within the same line the computer sends an update of
the cursor position.

Regardless of the mode, the computer always send an
updated line if the content has changed.


-------------------------
If a wrong protocol package is send
the Logtext will go into an error mode
and stop receiving.

Key pressed on Logtext comes as ANSI codes.
Press dot 1 gives 'a' and 12 gives 'b'.
Cursor movements comes as ANSI starting with 0x00.