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* * SPP (STANDARD PARALLEL PORT) ADAPTER BOARD * *

A project log for 68k-MBC: a 3 ICs 68008 homebrew computer

An easy to build homebrew SBC with a 68008 CPU. Two HW options: Lite and Full. Lite allows to build a 3 ICs 68008 system running CP/M-68K.

Just4FunJust4Fun 10/10/2021 at 09:032 Comments

* * SPP (STANDARD PARALLEL PORT) ADAPTER BOARD *  *

The Standard Parallel Port (SPP) Adapter board allows to use the GPIO port of the 68k-MBC as a standard printer parallel port.

In this way you can use a legacy parallel (Centronics) printer.

To connect the SPP Adapter board to the GPIO connector of the 68k-MBC board you need a 10cm long 20 wires flat cable terminated with an IDC connector at both sides (pay attention to connect the cable in the right way on both sides, so the pin 1 on the 68k-MBC GPIO connector corresponds to the pin 1 on the SPP Adapter board GPIO connector).

Please note that you have to power off the 68k-MBC board before connecting or disconnecting the SPP Adapter board to it.


NOTE:
before using the SPP Adapter board (A240721-R270921) you have to update both the IOS firmware and the SD image to the latest available version (see the FILES section).

In the following image the SPP Adapter board with the flat cable (connected to the GPIO connector of the 68k-MBC) and with the printer cable:

The cable to use for the printer is the common parallel printer cable, with a DB-25 connector at one side and a Centronics connector at the other:


HOW TO BUILD IT

In the FILES section you can find a zip file with all the documentation needed to build the SPP Adapter board, including the Gerber files for the PCB production.


HOW TO USE IT: THE SPP CP/M-68K UTILITY

To enable the SPP Adapter board under CP/M-68K I've added on the drive B: the custom utility SPP.68K (and the source SPP.BAS).

You have to execute the SPP utility to enable the SPP Adapter board and "link" to it the LPT: CP/M device inside CP/M-68K. After the execution of the SPP utility the GPIO port will be linked and reserved (the "normal" GPIO opcodes/functions inside IOS will be disabled) to the SPP parallel port emulation until a system reset or reboot:

After the execution of the SPP utility you need to link the LST: logical device to the LPT: device with the CP/M command STAT LST:=LPT:


At this point you have a working printer parallel port on LST:, so if you give the Ctrl-P command all the console output will be echoed to the printer:


NOTE:
The SPP utility will output an error message if the GPE (GPIO Expansion) option is not installed.


HOW TO USE IT: GCC EXAMPLES

I've added a couple of source examples in the SD image (/gcc-68k/workdir directory) to show how to use the SPP Adapter with the gcc cross compiler.

The two source examples are getStatusSPP.c and writeTestSPP.c, and they are the ones I used for the first test of the SSP Adapter board:


WHERE TO GET A PCB

I've prepared an "easy" link to get a small lot (5 pcs minimum) of PCB of the SPP Adapter. The link is this one.


HOW TO GET A KIT OR AN ASSEMBLED UNIT

TBD

Discussions

sq9pxb wrote 10/21/2021 at 10:17 point

Can I connect to the GPIO in the V20-MBC? Is there any software to emulate an SPP printer in CP / M-86?

  Are you sure? yes | no

Just4Fun wrote 10/21/2021 at 11:42 point

Yes, you can connect it to the GPIO of the V20-MBC (or Z80-MBC2), but you have to write a program (driver) to use it or (better but more complex) modify the IOS FW and the BIOS for a complete support inside CP/M (the same I'll do for CP/M-68K here for the 68k-MBC) . I currently haven't the time to backport it on the previous boards and CP/M "flavors".

  Are you sure? yes | no