AWalker@rutgers.arpa (04/28/83)
From: Hobbit <AWalker@rutgers.arpa> This is a copy of a message I sent to someone earlier, about hacking an Epson HX-20. I like the little box; it has a lot of really winning things designed into it, and it is at least easy to find where its limitations *are* fairly quickly without a lot of thrashing. -------- Well, so far so good. I found the Epson manuals quite thorough, and could do useful things in short order by looking a few things up. As far as downloading is concerned, the first thing to do was make a compatible cable for the rear end of the thing. Do you know how hard it is to find a DIN-8 connector??? No wonder Epson wants $60 for their custom-hacked cable, and it wouldn't have worked anyway with our setup since the Epson doesn't see signal ground from AC ground like everything else. I finally found a plug for it, but it was the wrong type. I forced the issue by bending and grinding down two pins so it would fit the jack on the back of the micro. Writing a terminal program, and then a downloader, was trivial. You simply open the RS232 port as a file device in Basic, and do line inputs to a huge array, and the write the results to the microtape. However it must see all lines beginning with line numbers, or it will not subsequently load the program. To prepare a BASIC program for downloading, I tacked the string <EOF> on the end, and made the downloader look for that to signal end of file. The Epson is a slow machine, so it can only handle LINE INPUTS at the RS232 interface at 300 baud max. This is the only lose as I see it. This also involves not echoing *back* from the RS232 port, since there is a 6-character or so typeahead buffer, and while you are echoing something back, input is already piling up for the next LINE INPUT. It's best to do nothing but receive for effective downloading, if you're not using something smart on the sending end. With the above described setup, I simply had the Epson tell the host ''TYPE <file>'', and then snarf up lines till it hit that <EOF> thing. So far we've loaded a 4K or so model, in very tight code with no spaces, that was generated by another Expert program. We are supposed to be getting a 16K expansion box, so we can theoretically get 32K worth of BASIC stuffed into it. --------- _H* -------