making HP39GS Serial Cable (RS-232)

[ilkka777]

(05-07-2019 05:51 AM)ilkka777 Wrote:  

(05-07-2019 05:10 AM)cyrille de brébisson Wrote:  Hello,

Depending on the cals, the higher level protocols will be either an improved version of X-modem or Kermit...
Some other logical data can be exchanged to do directory listing and the like.

Cyrille

Hp39GS, HP40GS and HP50, assuming they all use the same. These are newer calculators, what do you think about the protocol?

Also the Baud rate would be important to know in order to sniff the protocol details, if you know it?

now im getting like 2 bytes of data or so from receiving calculator (clear to send signal??) but not sure is it correct because it looks like question mark mirrored (?, but mirrored), In HEX its like 3E3E so it looks like a pattern. Not sure it is just gibberish though. Tried to use several different baud rates.

Edit: I had error, corrected

Ok, I was wrong (got bug with character conversions), it sends first character "D" three times and then NAK, could it be possibly negotiating the protocol this way? Tried to send NAK the receiving HP39GS but it sends weird set of frames -- does not look like X-Modem to me? Can anyone know the protocol?

https://pythonhosted.org/xmodem/xmodem.html

http://web.mit.edu/6.115/www/amulet/xmodem.htm

Edit: removed some text which was error, my program read false characters leading to wrong conclusion