Stefan,

Proper documentation is always a pain in hobby projects... ;-)

0. The original Intel Basic52 manual applies (see e.g. here), plus the extras I added, as described on the "changes" page. Not very wordy, but the core information is all there.

1. I2C extension... B52 has a concept of extensions - there is an interface through which you can add BASIC commands/keywords (simply attaching an EPROM in the original concept - or just a piece of code in the 'RD2). There are two "positions" for extensions, mapped at 2000h and 4000h. There are a few extensions around already, providing more or less interesting features. One of these came with the Elektor version of B52 by H.Boehling and implements four BASIC commands for simple bit-banged I2C. Look inside the zipfile to which I gave the link above, there is the asm source of that extension there. Simply assemble it and merge the resulting hex with the hex of B52/RD2 from my site.

2. Simply as if you would type it in - use the "send file" facility of your terminal emulator. There are a few dedicated BASIC52-terminals around which are aimed at more luxurious BASIC program upload/download, but I only briefly tried one or two - I am not interested, the general terminal approach is more than enough for me.

3. Yes, of course; but there is no built-in comfortable provision for that. On the other hand, you have almost 32kB FLASH available for BASIC programs, I think that's more than enough for most purposes.

JW