1   How_it_started

Many years ago I bought Omen Kilo (SBC with HD6309) and start to play with it. It worked, but did not anything visible (does it even run?), just communicated over Serial. Which was not so much satisfying.

So I invented and constructed card for 8 serial channels and called it Expanduino (pages in Czech only and incomplete), as it was Arduino based.

It worked somehow, but was mechanically unreliable, slow and did not allowed for more extensions.

So I decided to make my own design from the start and make it simply extensible, so it culd have everything a computer needs - output to some monitor, input from keyboard, filesystem to store and load data and programs, ports and so on and so on. This was not SBC anymore.

I also found Composite video from Arduino UNO from ceptimus and Squeezing Water from Stone 3: Arduino Nano + 1(!) Logic IC = Computer with VGA and PS/2 from slu4coder which looked like solution for the video output. I use their ideas (and many others) and reworked it to system, which can switch between VGA and RCA even on runtime. This looked as good foundantion for videocard I wanted.

First public presentation was on 2024 Maker Faire in Prague, in form of Computer at price for dinner as proof of concept.

I then expanded it to FORTH driven breadboard computer NanoHomeFORTH and started work on even better version with more RAM and power.

I called the project MegaHomeFORTH, as it was based on Arduino Mega, but then I discovered, that the most importaint pin (16MHz clock) is not accessible on Arduino Mega, nor on Arduino Mega Pro, so I went to make my own board, where it will be all included.

On that time the PCBway reached to me and told me, that the project prom Maker Faire catched their interest and that they will sponsor me with PCB for it, should I make the plans. I offered the new project instead, as it made more sense for me and they agreed. It took me 2 months to came with the first version MHF-001 and they manufactured the board for it.

The PCB was nice, simple to use, soldering there was easy for normal parts, but I had problems with the MCU and the RAM as the footprints I used was for machine soldering, but I had to solder this with my hands and eyes. MCU went well after lot of effort, but I could not solder the RAM reliably even after many attempts. It sometime worked, sometime not and sometime helped to press it with fingers. The pads for its pins was too small for me to make it reliable. The PCB itself managed well even when I repeatedly solder and desolder the pins, the problem was my handwork. Anyway it prove the concept, the RAM worked well sometimes.

Also other parts worked, it generated nice VGA signal with color lines, it generated RCA signal too, it read PS/2 keyboard and it even was able to read SD card while doing all the previous at the same time (I was using some Arduino library, where I hacked the millis() mechanism, as I used the interrupt for other purposes, I read one byte at time at each frame to do not collide with the VGA, so it got speed 50 char/sec, but it proved the concept).

I also published it as project there

There was problems with USB connector, mainly because small footprint, it was torned from the PCB more time due my manipulation and was not as reliable as I wanted, but the desing did not allowed for other connection to MCU (except for ISP programming), so new concept for that was included to the new step too.

So I took another 2 moths to redesign it, added more features, made more logical configuration, and improved everything I could and now I am here, with MHF-002, which have more circuits on it, new module for USB, debug NeoPixel LEDS and so on and so on, which PCBway also offered to manufacture for free as sponsoring - and it is just manufactured as I write this lines :)

Here is 3D model, how it will look fully assembled:

I am looking for bring real photo soon :)