This is a fun project based on an Intel P8031 processor (may be any higher version such as 8051, 8052, etc.) a small 8031 shield and an Arduino Mega board. This allows you to experiment with a real 8031 processor where the ROM, external RAM and serial I/OI are all provided by the Arduino Mega. In effect, this gives you an 8031 based computer, with up to 64KB of ROM, 6KB of external RAM and serial I/O. In addition, you have all pins of P1 open to connect external hardware to it and all other connections of the 8031 processor are also routed out. I myself threw the software that originally came with the 8031 retroshield into the trash and wrote new Arduino software. This has been improved on many points and no longer needs external libraries.
In addition, a Paul Monitor was included as standard, but you can’t do much with it. It’s nice that it works but it’s not a nice demo. I decided to dust up an old version of Tiny Basic that I had once modified. This was a bigger job than I imagined, I also wanted the code to run on a bare 8031 with 128 bytes of ram and for that everything had to be rewritten to the external ram. I also did a major code cleanup and organized and formatted the code neatly and clearly. On this page I provide a zip file with the source code of the basic interpreter in 8031 assembly.
Hardware
The hardware you need is an 8031 retroshield, which you can order HERE. You also need an 8031 processor, which I sell in my webshop, and you need an Arduino Mega board. One of the minor tweaks I made to the hardware is on the 8031 retroshield. According to the datasheet, the X1 pin must be grounded when the 8031 is controlled with an external clock. The photo shows how I did this on the back of the PCB with a solder bridge.
So I did this and so I only had to solder the resistor for the X2 line. The rest of the capacitors, the resistor and the LED are actually superfluous and I didn’t install them either. I did use a socket for the processor and soldered a series of pins on both sides so that I can easily connect external hardware, or for example a row of LEDs.
The result is impressive, the code works fine on the 8031 Arduino Mega computer and there is a small demo program included in the rom. When you compile the sketch and send it to the Arduino Mega, it works “out of the box”. This is an example using the Arduino IDE.
Links and downloads
- Here you can order the 8031 shield in Germany (www.pcb4diy.de)
- Homepage of the original Arduino Mega Retroshields site
- Here you can download the complete Arduino sketch for this project as a zip file.
- Here you can download the assmbly source of the TB31 basic interpeter as a zip file.
- Here you can download an open text document with the manual of TB31.
