The Standard Parallel Port (SPP) Adapter board allows to use the GPIO port of the "retro-board" 68k-MBC SBC (Single Board Computer) 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 of the main project page).

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 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 connector will be linked and reserved (the normal GPIO opcodes/functions inside IOS will be disabled) to the SPP parallel port 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:

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 testing of the SSP Adapter board:

NOTE: All the files, updates and the details to build it are in the 68k-MBC page here:

https://hackaday.io/project/177988-68k-mbc-a-3-ics-68008-homebrew-computer/log/198836-spp-standard-parallel-port-adapter-board