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Parallel Port Adapters |
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If you are installing parallel port adapters it means you are probably messing |
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around with wires and IC's and the like. If you have purchased a card that |
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provides an external i2c/smbus this will require combined algorithm and |
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adapter code in a single module. |
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If you are doing it yourself by using the parallel port there |
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are basically 2 options. |
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1) Using the parallel port and using the i2c-pport adapter module and the |
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i2c-algo-bit algorithm module together to enable you to wire up your parallel |
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port to act as an i2c/smbus. This provides a bus that will enable most |
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sensors to work but doesn't support the entire i2c/smbus capability. |
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2) Using the parallel port to interface to a Philips PCF8584 parallel to i2c |
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adapter chip. You will need to build a bit of a circuit to do this. This |
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configuration needs the i2c-pcf-epp adapter module and the i2c-algo-pcf |
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algorithm module. This support almost all of the i2c/smbus capabilities. |
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i2c-pport Documentation |
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----------------------- |
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This is a primitive parallel port driver for the i2c bus, which exploits |
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features of modern bidirectional parallel ports. |
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Bidirectional ports have particular bits connected in following way: |
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/-----| R |
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--o| |-----| |
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read \-----| /------- Out pin |
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|/ |
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- -|\ |
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write V |
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--- |
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It means when output is set to 1 we can read the port. Therefore |
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we can use 2 pins of parallel port as SDA and SCL for i2c bus. It |
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is not necessary to add any external - additional parts, we can |
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read and write the same port simultaneously. |
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I only use register base+2 so it is possible to use all |
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8 data bits of parallel port for other applications (I have |
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connected EEPROM and LCD display). I do not use bit Enable Bi-directional |
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Port. The only disadvantage is we can only support 5V chips. |
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Layout: |
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Cannon 25 pin |
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SDA - connect to pin 14 (Auto Linefeed) |
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SCL - connect to pin 16 (Initialize Printer) |
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GND - connect to pin 18-25 |
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+5V - use external supply (I use 5V from 3.5" floppy connector) |
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no pullups requied |
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Module parameters: |
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base = 0xXXX |
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XXX - 278 or 378 |
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That's all. |
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Daniel Smolik |
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marvin@sitour.cz |
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