andrew@earwax.pd.uwa.oz.au (Andrew Williams) (10/18/90)
Hi- I'm trying to build a receiver for the infra-red printer output on my HP28S. The data seems to be RS232 protocol, but getting the frequency right is a bit tricky. I assume thats its a carrier of around 40kHz, with a couple of signal tones for 1 and 0 around a few hundred Hertz. Does anyone out there know the exact frequencies, for both carrier and signal? (I dont have a storage CRO, and its pretty tricky triggering properly without one). With a bit of luck, I'll be able to make a 'Infra-red to RS232' converter, and keep up with the 48 owners (at least partially)! Andrew Williams, Physics Department, University of Western Australia. (andrew@earwax.uwa.oz.au)
chuck@mitlns.mit.edu (10/19/90)
-Message-Text-Follows- In article <andrew.656252611@earwax.pd.uwa.oz.au>, andrew@earwax.pd.uwa.oz.au (Andrew Williams) writes... >Hi- I'm trying to build a receiver for the infra-red printer output on my >HP28S. The data seems to be RS232 protocol, but getting the frequency >right is a bit tricky. I assume thats its a carrier of around 40kHz, with >a couple of signal tones for 1 and 0 around a few hundred Hertz. Does >anyone out there know the exact frequencies, for both carrier and signal? >(I dont have a storage CRO, and its pretty tricky triggering properly >without one). With a bit of luck, I'll be able to make a 'Infra-red to >RS232' converter, and keep up with the 48 owners (at least partially)! > Andrew Williams, > Physics Department, > University of Western Australia. > (andrew@earwax.uwa.oz.au) HP has a news letter that they publish, in it several years ago they gave a complete spec. I did it from a scope and it was damn hard but kind of fun to crack. It's a great way to get data out of your microprocessor project. Get the newsletter from HP for the real dope, but if you can't wait I'll follow with a bit of what I remeber, don't count on it being absolutly accurate I don't remeber so well after 2 years. This is what I remeber. Tone 32,768 Khz I'm pretty sure, I remember the striking match to a power of 2. I assumed it was to match up with the cheap crystals they use in watches. since I got it off a scope I only had it to 1% or so 8 bit ascii data with 4 error correction bits, also a 1 1/2 bit introduction bit. The correction bits come first. To generate the error correction bits you need to figure out 4 1 byte numbers. I did it by printing out the alphabet and figuring it out, HP has it in there news letter article. Basically each ECC bit is: BIT_i = PARITY(CODE_i.AND.ASCII) At least thats what I did, I'm sure ther are other ways of calculating it that look quite different but give the same result. The ones and zeros are sent as follows (S=silience T=carrier) tone, what is important is the is the transition between time slices 2 and 3, does it go tone to silence or silence to tone? 1 = SSTS 0 = STSS The tone bursts a 7 cycles long I think Chuck@mitlns.mit.edu
kenw@col.hp.com (Ken Wyatt) (10/23/90)
This was detailed in the "Hewlett-Packard Journal", August 1987 issue. Try contacting your local HP sales office and I'm sure they could get that issue for you. Ken
akcs.007@hpcvbbs.UUCP (greg sheka) (11/05/90)
I just wanted you to know that I just completed a IR to RS232 converter
for my HP48. I'm doing it for a senior design project. It works really
well with mskermit. I currently have a range of about 8". I talk to HP
and asked for a the IR format and they sent me a I/O specifications
sheet.
Greg J. Shekasteve@altos86.Altos.COM (Steve Scherf) (11/06/90)
In article <273510a1-3a1.2comp.sys.handhelds-1@hpcvbbs.UUCP> akcs.007@hpcvbbs.UUCP (greg sheka) writes: > > I just wanted you to know that I just completed a IR to RS232 converter >for my HP48. I'm doing it for a senior design project. It works really >well with mskermit. I currently have a range of about 8". I talk to HP >and asked for a the IR format and they sent me a I/O specifications >sheet. > > Greg J. Sheka How about posting the info here, or perhaps telling us how you got the info? Thanks in advance. -- Steve Scherf steve@Altos.COM ...!{sun|sco|pyramid|amdahl|uunet}!altos!steve These opinions are solely mine, but others may share them if they like.
fred@panther.mbir.bcm.tmc.edu (Fred Ledley) (11/06/90)
How about a post of the schematic? It would be great to be able to build an I/R receiver for my Macintosh and stop plugging and unplugging those cables. In the past people have converted schematics to sort of ASCII representation for posting on this board. Thanks! R. Mark Adams Baylor College of Medicine Department of Cell Biology fred@mbir.bcm.tmc.edu
winters@Apple.COM (Steve Winters) (11/07/90)
In article <273510a1-3a1.2comp.sys.handhelds-1@hpcvbbs.UUCP> akcs.007@hpcvbbs.UUCP (greg sheka) writes: > > I just wanted you to know that I just completed a IR to RS232 converter >for my HP48. I'm doing it for a senior design project. It works really >well with mskermit. I currently have a range of about 8". I talk to HP >and asked for a the IR format and they sent me a I/O specifications >sheet. > > Greg J. Sheka Would you be willing to publish the design when you are through? I'm sure a number of people would be interested. Steve Winters winters@apple.com