Re: IR printer data format (from 42 etc) Message #3 Posted by Andrés C. Rodríguez on 6 Mar 1999, 10:03 a.m., in response to message #1 by simon bridger
There was an HP Journal issue, about 1998, in which the IR pulses coding of the calculator-to-printer link was described. I recall a strange detail, the checksum was computed by means of a AND function, instead of the usual XOR (XOR is normally preferred because it maintains more information content than AND). If you read my "guest contribution" (here at this Museum), you'll see that I tried, in time, to made some kind of external hookup to my HP 25, and later to my 41C. While not included in that article, I had also tried to pick IR pulses from my HP 42S with a simple phototransistor circuit, and to so "upload" the pulses to a PC. Although part of the experiment worked, I was not able to pursue it much after the first trials (around 1991)...
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