07/30/2020 at 12:53 •
Progress is slow, but the project is not dead!
I just have very little time in the past months because of a little addition to our family.
This project requires me to be able to work on it for periods of several hours straight and that's just not happening right now.
I did come to the realization that the pin headers that I'm using to interconnect all the PCB were not sufficient; it did not have enough pins.
That forced me to redo some of the work I had previously done on the circuit designs.
There are now two 64-pin headers in place which should be enough.
Just to be sure I will not do any PCB design until all the circuit schematics are done.
To be continued some day...
05/12/2020 at 15:36 •
Because running programs in the Logisim circuit is incredibly slow, I decided to write an emulator for the DM-02.
The emulator features a (separate) text and video display, just like the Logisim circuit does. The only difference is that this video display supports 240x200 pixels instead of the puny 128x128 from Logisim.
Programs need to be assembled first before they can be loaded into the emulator to run. There is currently no option for editing programs from inside the emulator.
If you'd like to give it a go, the emulator is available online: https://dutchmaker.com/dm-02/emulator/
Code can be found in the GitHub repo.
05/03/2020 at 12:52 •
Added an LCD to the Logisim circuit and wrote a program that outputs a 64x64 black and white bitmap image on it.
Although the LCD has a 128x128 resolution and supports 16 bits colors, filling the entire screen would be painfully slow and color was ditched as well for that reason.
It was a good chance to test some more of the assembler and got a few bugs squashed in the process.
It also allowed me to test the general idea I had for a simple video card, which now looks very do-able.
I also received the first couple of PCB so the actual machine will now slowly start to be built.
The computer will consist of several stacked modules that are interconnected by pin socket with long pins, as such:
Not sure how many modules I'll end up with yet. The only one designed so far are the debugger (which is not more than a few sockets that hold an Arduino Mega that is connected to all the interconnected pin sockets) and the power & clock circuit that I still need to assemble. The bottom plate is empty and only meant as, well, bottom..
I'll try to publish some more updates as they happen in the coming time.