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Revision 3567, 1.2 KB
(checked in by mds, 12 years ago)
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updates to pport docs from Daniel Smolik
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Property svn:eol-style set to
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Author Date Id Revision
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| 1 | Primitive parallel port is driver for i2c bus, which exploits |
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| 2 | features of modern bidirectional parallel ports. |
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| 3 | |
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| 4 | Bidirectional ports have particular bits connected in following way: |
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| 5 | |
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| 6 | | |
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| 7 | /-----| R |
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| 8 | --o| |-----| |
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| 9 | read \-----| /------- Out pin |
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| 10 | |/ |
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| 11 | - -|\ |
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| 12 | write V |
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| 13 | | |
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| 14 | --- |
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| 15 | |
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| 16 | |
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| 17 | It means when output is set to 1 we can read the port. Therefore |
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| 18 | we can use 2 pins of parallel port as SDA and SCL for i2c bus. It |
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| 19 | is not necessary to add any external - additional parts, we can |
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| 20 | read and write the same port simultaneously. |
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| 21 | I only use register base+2 so it is possible to use all |
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| 22 | 8 data bits of parallel port for other applications (I have |
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| 23 | connected EEPROM and LCD display). I do not use bit Enable Bi-directional |
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| 24 | Port. The only disadvantage is we can only support 5V chips. |
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| 25 | |
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| 26 | Layout: |
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| 27 | |
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| 28 | Cannon 25 pin |
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| 29 | |
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| 30 | SDA - connect to pin 14 (Auto Linefeed) |
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| 31 | SCL - connect to pin 16 (Initialize Printer) |
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| 32 | GND - connect to pin 18-25 |
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| 33 | +5V - use external supply (I use 5V from 3.5" floppy connector) |
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| 34 | |
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| 35 | no pullups requied |
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| 36 | |
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| 37 | Module parameters: |
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| 38 | |
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| 39 | base = 0xXXX |
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| 40 | XXX - 278 or 378 |
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| 41 | |
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| 42 | That's all. |
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| 43 | |
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| 44 | Daniel Smolik |
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| 45 | marvin@sitour.cz |
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