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I have a small board that controls some appliances through the parallel port.

What i want to do is to put on high/low pin X with out modifying the rest of the pins (short story, control each pin individuality)

Example: D0-D5 = 1 what i want D0 = 0 and D1-D5 = 1

Thanks a lot.

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  • \$\begingroup\$ Which OS? Which language. C++ Boost library has a very open license, is cross-patform and very reliable. It has a asio module, which I am currently using to cotnrol a serial port (webalice.it/fede.tft/serial_port/serial_port.html). Maybe this could work out for the parallel port too. Good luck! \$\endgroup\$ – Vorac Sep 12 '12 at 7:46
  • \$\begingroup\$ Also google search for "parallel port terminal" (without the quotes) turns up loads of results. Haven't researched them, however. \$\endgroup\$ – Vorac Sep 12 '12 at 7:48
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Usually in this situation I keep a variable with the whole byte, change the bits I want and then write it back to the port.

Example in C:

PortValue = 0x00;    // Set all bits to 0
LPT = PortValue;

PortValue |= 0x01;   // Set the bit 0 to 1
LPT = PortValue;

PortValue &= ~0x01;  // Set the bit 0 to 0
LPT = PortValue;
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