Serial interface ticket printer prints garbage, doesn’t cut, or performs unreliably

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POS printers with a serial interface can sometimes perform unreliably because they are incorrectly set up. Serial interface printers are typically used in locations where a computer is over 10 feet from the printer because the cable can be much longer than with a printer connected to a parallel (standard printer) port or USB port.

Unreliability, if it occurs, is more likely the larger an order grows. Symptoms will include printing of unrecognizable or random “garbage” characters and a failure to cut the ticket on printers equipped with a cutter.

This problem is caused by a buffer overrun in the printer — The computer fails to stop sending information to the printer when the printer cannot accept additional information to print. This is a computer/printer problem and is entirely unrelated to Point of Success.

Correct this problem by matching the flow control (also called handshaking) between the computer and printer.

Changing printer flow control: See your printer’s user manual for information on the location and setting of the printer’s dip switches.

Changing computer flow control: Open the Properties window for the serial printer. Click the Port tab, then choose the flow control setting that matches your printer’s setting. The two available flow control settings are XON/XOFF and Hardware (also called DTR/DSR).

Note: All serial communication settings must match between the computer and printer, including bits per second (also called data rate, which is the communication speed), data bits, parity and stop bits. The default settings for these items will normally work without changes.

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