jdsb@coachk.egr.duke.edu (John D. S. Babcock) (03/22/91)
One of my professors teached a VLSI design class in which we fabricate a 2000 transistor chip. Since each student must come up with a semester project, he was suggesting an infrared receiver to receive the 48SX I/R, decode the kermit protocol, and send the data to a PC. I know you can do kermit on a PC, but he wanted the kermit implemented on the CMOS chip. All this so you don't have to plug in a three wire I/O port. Go figure. However, it would be kind of fun to design. 1. Are there I/R receivers that take care of most of the conversion so all you have to work with is digital signals? 2. Could Kermit be implemented in fairly simple logic (i.e. via a complex state machine)? 3. Where would he find a Kermit specification? 4. Which book would have enough detailed specifications for the 48SX infrared I/O port to make an interface that would receive from the 48SX? 5. Do I need two way I/R to do Kermit? 6. What I/R projects is anyone out there working on? How much sucess have you had? Please email responses. Email if you want a summary. Thanks!! ------------------------------------------------------------------------- J. D. Sterling Babcock Duke University Electrical Engineering jdsb@dukee.egr.duke.edu or jdsb@egr.duke.edu or att!egr.duke.edu!jdsb
akcs.jwtrav@hpcvbbs.UUCP (John Wettroth) (03/30/91)
The HP-48 ir couldn't be simpler. Look at it on a scope. It is just a uart driving an led. Receiving the ir over short distances can be done easily with a photo-transistor. The book referenced in 48 manual about Kermit (by Cruz) has more in it about Kermit than any human could ever want to know. Its about $30 at any good college bookstore. Kermit needs a microcomputer to implement, a state machine doesn't make much sense. As far as my luck with HP-48 ir, I sell a small data acquisition and control system (available from Edu-Calc) that is controlled over the IR link. Good luck.
s2499576%techst02.technion.ac.il@TAUNIVM.TAU.AC.IL (Yaniv Shaya) (03/31/91)
Is it possible to build an amplifier for the IR, so it would be possible to transmit and receive from longer distances (few meters), It could be useful to many people (specialy students). ???? Think about it !
pashdown@javelin.es.com (Pete Ashdown) (04/01/91)
s2499576%techst02.technion.ac.il@TAUNIVM.TAU.AC.IL (Yaniv Shaya) writes: >Is it possible to build an amplifier for the IR, so it would be possible to >transmit and receive from longer distances (few meters), It could be useful >to many people (specialy students). ???? Why don't you just ask the professor to write the answers to the test on the chalk board? Then you don't have to do any learning AT ALL! -- "Why can't I be you?" - Robert Smith "Why can't he be you?" - Patsy Cline "Why can't you be you?" - `Seven Faces of Eve' Pete Ashdown pashdown@javelin.sim.es.com ...uunet!javelin.sim.es.com!pashdown
Yaniv Shaya <s2499576%techst02.technion.ac.il@TAUNIVM.TAU.AC.IL> (04/02/91)
Well, I asked, but he didn't want to, so I try different approaches.
darrylo@hpnmdla.hp.com (Darryl Okahata) (04/03/91)
In comp.sys.handhelds, akcs.jwtrav@hpcvbbs.UUCP (John Wettroth) writes: > The HP-48 ir couldn't be simpler. Look at it on a scope. It is just a > uart driving an led. Receiving the ir over short distances can be done While the I/R interface on the HP-48SX is not complex, it's not trivial either. It's also not an "UART driving an LED". The output from the HP-48SX LED consists of very narrow *pulses*, and is not directly compatible with an RS/232 interface. You need some fairly simple circuitry (basically, a digital one-shot) to lengthen the pulses into something that most RS/232 interfaces can handle. Back in August/September 1990, Tony Duell (ard@pva.bristol.ac.uk) of the University of Bristol, England, posted a schematic for a bidirectional I/R <--> RS/232 interface. I haven't tested it, but it looks useful. Some of the parts may be difficult to locate, but experienced designers should have no trouble working around that. If anyone wants a copy, send email (I don't think this newsgroup is archived anywhere). See the (unsupported) "HP-48 I/O Technical Interfacing Guide" for more information. ASCII versions of this short document were posted here, and should still be available on the HP BBS. The troff sources, which requires the pic processor, are available via anonymous ftp from the HP BBS (hpcvbbs.cv.hp.com -- 15.255.72.16). I've forgotten the name of the file, offhand. -- Darryl Okahata UUCP: {hplabs!, hpcea!, hpfcla!} hpnmd!darrylo Internet: darrylo%hpnmd@relay.hp.com DISCLAIMER: this message is the author's personal opinion and does not constitute the support, opinion or policy of Hewlett-Packard or of the little green men that have been following him all day. Also, the author, while being an HP employee, has absolutely no connection with the calculator folks.
akcs.jwtrav@hpcvbbs.UUCP (John Wettroth) (04/11/91)
actually the last response is correct. the ir is simple once you've got a handle on it. my real answer should have been that the ir consists of 52 microsecond pulses of light for logic ones but other than that is much like the output of a standard uart. a project for your vlsi class that might be interesting and fun would be to make a "uart" that could receive hp ir and stretch it to times that would be compatible with a standard uart (like those in a pc). the way this could work would be to have a latch that would take the ir and get set and have a counter that would come by every 420 microseconds (2400 baud) and sample it. standard uarts sample at the center of a bit period after getting sync'ed on the start bit. your uart would sample at the center but the input would be latched. this latch would be reset shortly after a sample for the next sample. do this 11 times and pass through the output, level shift with something like a maxim max-232 chip and you would have rs-232 that could go into a pc. this kind of stuff is easier to do with a micro-controller using interupts but would be a good exercise for anyone. good luck and thanks to the last responder for the clarification.