|Re: HP82164A HP-IL/RS-232C interface|
Message #6 Posted by Tony Duell on 11 Feb 2011, 4:29 a.m.,
in response to message #3 by Andrés C. Rodríguez (Argentina)
From what I remember, Epson made at least 3 diffferent RS232 interfaces for the MX/RX/etc printers. As you said, the standard printer firmware included a (bit-banged, IIRC) serial interface, and the simplest RS232 board enabled this (IIRC by grounding a pin on the conenctor for the interface PCB) and converted between RS232 levels and TTL. Configuration (baud rate, etc) was done by DIP switches on the board, read via the (redundant) parallel input port.
The other 2 RS232 boards had microcontrollers and buffer RAM on them and did a full serial-parallel conversion. The printer was left as a normal parallel device.
Epson also made an HPIB/GPIB/IEEE488 interface. It does the address comparison, handshake, etc and just feeds the data to the printer as a parallel device.
Those are not easy to find, but much harder to find still is the HP HPIL interface board. It was part of the HP82905 printer, but it will work in many older Epsons. IIRC, it's a microcontroller and a 1LB3, basically.