root/i2c/trunk/doc/i2c-pport @ 3567

Revision 3567, 1.2 KB (checked in by mds, 13 years ago)

updates to pport docs from Daniel Smolik

  • Property svn:eol-style set to native
  • Property svn:keywords set to Author Date Id Revision
Line 
1Primitive parallel port is driver for i2c bus, which exploits
2features of modern bidirectional parallel ports.
3
4Bidirectional ports have particular bits connected in following way:
5   
6                        |
7            /-----|     R
8         --o|     |-----|
9      read  \-----|     /------- Out pin
10                      |/
11                   - -|\
12                write   V
13                        |
14                       --- 
15
16
17It means when output is set to 1 we can read the port. Therefore
18we can use 2 pins of parallel port as SDA and SCL for i2c bus. It
19is not necessary to add any external - additional parts, we can
20read and write the same port simultaneously.
21        I only use register base+2 so it is possible to use all
228 data bits of parallel port for other applications (I have
23connected EEPROM and LCD display). I do not use bit Enable Bi-directional
24 Port. The only disadvantage is we can only support 5V chips.
25
26Layout:
27
28Cannon 25 pin
29
30SDA - connect to pin 14 (Auto Linefeed)
31SCL - connect to pin 16 (Initialize Printer)
32GND - connect to pin 18-25
33+5V - use external supply (I use 5V from 3.5" floppy connector)
34     
35no pullups  requied
36
37Module parameters:
38
39base = 0xXXX
40XXX - 278 or 378
41
42That's all.
43
44Daniel Smolik
45marvin@sitour.cz
Note: See TracBrowser for help on using the browser.