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Some time ago we introduced a tiny tool called ppmview.prg in our collection of tools and progs for our Steckschwein. The ppmview.prg, as the name already tells, is able to load an image in ppm (Portable BitMap) format with a maximum size of 256x212px and displays it on the screen.

The first version of ppmview was released in 2018 and since then we just use the SCREEN 8 (MSX) also known as graphic mode 7 (RGB).
Mode 7 is a bitmap mode where we have 256 colors available and each pixel requires 1 Byte for their color information. The 1 Byte color information must be stored in VRAM encoded as GRB 3:3:2 (green, red, blue), which means 3 Bit green, 3 Bit red and 2 Bit blue.
On the other side we have the PPM color information - which is 24Bit RGB - so we have to adapt or map the 24Bit to our 8 Bit GRB color value in some way.
It becomes apparent that this comes with a price, namely the loss of color information. Especially the blue part of the pixel is just 2 Bit, hence we have 4 levels of blue per pixel available only. The following screenshot from our Emulator shows the loss of color information.

Niklaus Wirth has died on 1.1.2024 at the age of 89. Known to most as the creator of the programming language Pascal, Wirth was also primary designer of the programming languages Euler, PL360, ALGOL W, Modula, Modula-2 and Oberon, heavily influencing coming languages and the paradigm of object oriented programming, and programming methodology altogether. Furthermore, he led the team designing the Lilith workstation, a graphical workstation with a bitmapped graphical display, heavily influenced by the Xerox Alto.

In order to fill the void in the days between Christmas and New Year’s Eve 2013, we began experimenting with a 65C02 on a breadboard. This little experiment would later evolve into an actually working 8bit computer. 10 years and some significant amount of focus creep later we had build this cool little 8bit machine with the specifications found here.

The amount of new stuff to learn to design a new computer out of “old” or “retro” components was massive. We went about it as rather electroics noobs who only had basic knowledge about anything. We did not have a lot of experience with circuit board design. We did some assembly coding on the C64, but nothing as big and complex as a FAT32 filesystem, let alone some sort of an operating system, albeit a rudimentary one.

Our FAT32 driver now supports byte-wise writing of a file. Reason enough to continue reworking the file handling of our EhBasic port that we started here to finally having the SAVE command write ASCII source files.

The basic idea is to open a file, redirect the EhBasic output vector to our new kernel call “krn_write_byte”, then trigger the LIST command internally. The listing being output by LIST will then be written to the opened file instead the screen. Finally, once LIST is done writing, close the file and return.

For reasons mostly related to the pandemic, we did not attend VCFb since 2019. Finally, this year we managed to be there again, just im time to show our newly assembled rev0.6 (and fully working !!!) SBC boards around, and have tons of fun with other very nice people there (Hello https://mega65.org/!). Also, we talked about how the Steckschwein evolved over the last almost 10 years and about our development methodology. As always at VCFb, the talk was streamed and the video is available at media.ccc.de. Our slides from our talk can be downloaded in PDF format here and here.

After some troubleshooting, we finally finished Revision 0.6 of our boards, and the new boards are finally there, ready to be assembled. We managed to fix all the issues we found, and also did some cleaning up, used better footprints for the resistors and the mini DIN jacks.
Soldering session coming up..

Revision 0.6 boards are there