GPIB (IEEE-488) to Centronics (IEEE-1284 SPP) Protocol Converter

This is a work in progress. It has stalled at the moment as I have lost access to a test environment. The incomplete code is NOT available.

Introduction

This article describes a current project to implement a GPIB to Centronics protocol converter, for emulating a GPIB printer interface.

The application of particular interest in to allow screen printing from HP Spectrum Analysers to a low cost HP DeskJet printer, or any other printer supporting PCL.

The design in implemented in an Atmel AVR chip, an AT90S8535 which has four 8 bit ports providing enough capacity for data and control leads on both interfaces without multiplexing.

The prototype was based on a Lawicell prototype board for the Atmel AT90S8535, and contains the MCU, power supply regulator, and Kanda style In System Programming connector. The case houses the board, DB25F connector for the printer, a IEEE-488 connector for the GPIB bus, DC inlet jack, and the switches and LED.

Fig 1: Prototype

The menu is activated by holding the Menu key in while pressing and releasing the Reset key. The LED will flash once per second indicating the menu option, and the Menu key is then released after the desired number of flashes. For second level menus, the Menu key is pressed again and released after the desired number of flashes.

A quick flashing LED indicates an error, typically an invalid option. Some menu functions indicate that they have completed by turning the LED on solid. Press reset to resume normal operation. To abort menu selection, just press reset.

Print identification data
Inititialise Centronics printer
Print test pattern to Centronics printer
Hex dump mode (0/1)
Set GPIB address (1 - 7)
Set EEPROM to factory defaults
Test PCL substitution (debug only)