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Parallel Port

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Some older personal computers have a Parallel/Printer Port. This port is falling into disuse and USB is replacing it but USB to parallel port converters are available.

Running an older operating system like MS-DOS and programming in QBASIC, it is quite easy to use older hardware for control systems. Tasks like data logging are easier because the computer has disk storage.

Parallel Port Pinout

Parallel Port Features ...

The port uses a 25 pin D connector (DB25 - diagram above)
The parallel port is a memory mapped device
It is often called the printer port or LPT1
LPT stands for Line Printer
Three addresses are used
Address 378₁₆ is connected to eight output pins called D0, D1, D2, D3, D4, D5, D6, D7
Address 379₁₆ is connected to five input signal pins called S3, S4, S5, S6, S7
Address 37A₁₆ is connected to four input control pins called C0, C1, C2, C3
The ₁₆ means the number is hexadecimal.
If the port can be configured to be bi-directional so D0 to D7 can also be inputs.