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+--- Thread: 50g serial port tech. - Help. (/thread-7515.html)
50g serial port tech. - Help. - Vtile - 01-04-2017 03:52 PM
Hello, I have seen somewhere a techical specification for 50g serial port, something like serial communication manual or something on those lines, now I just can't find it on hpcalc.org. My memory says it did also had some form of HW specs for the port at some level.
I have basic knowledge of the port at the back of my head, but would be nice to read the manual/writing anyway.
I'm sure I have seen it there before ...somewhere.
.. Another question.. Can anyone see any pitfalls in HW hack that turns the (supposed) always on Vcc (directly from batteries) line off, while calculator is turned off ??? IIRC the SD card Vcc goes down with the calculator so basicly one N-channel 3.3V logiclevel MOSFET should do the trick ... Free space inside of the calculator is not a problem at all.
RE: 50g serial port tech. - Help. - Garth Wilson - 01-04-2017 07:51 PM
From my bookmarks:
http://hpmuseum.org/forum/thread-7009.html
http://commerce.hpcalc.org/serialcable.php
http://imgur.com/a/qR35j
https://www.allenwan.com/hpcalcserialcable/
RE: 50g serial port tech. - Help. - Vtile - 01-05-2017 01:38 PM
Thanks, those helps while not what I were searching for. To be fair, now I'm thought this a while I start to feel the document I remember seen somewhere propably were the hp50g IRDA-serial port tech abstract or similar. (Wondering if there could be any rumours of the part number of the IRDA transceiver/receiver module...) I'm extremely interested if it does have sensitivity control pin as do ie. Telefunken/Vishay TFDU4100 chip, that could explain the small operation distance (In Telefunken/Vishay TFDU4100 the DataSheet do say that SC high might (or will) introduce errors as:
Quote:The sensitivity control (SC) pin allows the minimum)
detection irradiance threshold of the transceiver to be
lowered when set to a logic HIGH. Lowering the
irradiance threshold increases the sensitivity to
infrared signals and increases transmission range up
to 3 meters. However, setting the Pin SC to logic HIGH
also makes the transceiver more susceptable to
transmission errors due to an increased sensitivity to
fluorescent light disturbances. It is recommended to
set the Pin SC to logic LOW or left open if the increased
range is not required or if the system will be operating
in bright ambient light.
PS. I just opened my calc and the GND line for the serial connector is directly from batteries with common wire, the Vcc comes from PCB.. So my easy MOSFET hack, wouldn't be that easy.
RE: 50g serial port tech. - Help. - rprosperi - 01-05-2017 02:23 PM
You may be thinking of this manual on hpcalc.org, "HP48 I/O Technical Interfacing Guide", however this is obviously for the HP-48, not the 50g.
RE: 50g serial port tech. - Help. - Vtile - 01-06-2017 01:44 AM
(01-05-2017 02:23 PM)rprosperi Wrote: You may be thinking of this manual on hpcalc.org, "HP48 I/O Technical Interfacing Guide", however this is obviously for the HP-48, not the 50g.
It might be it..
Oh, I'm scared that I fried it. CloseIO just out of nowhere did stop to work and Transmit line stays up.. While oddly the Transmit goes down as should while transmitting data, maybe more current on the control circuitry or pull down transisto...
Memory reset didn't throw the unworking closeio away, but even normal OFF closes the IO as CloseIO previously.. hmpf. I should have put those optoisolators BEFORE starting to toy around, couldn't resist. Well, AAAs and button cell out and Reflashing the ROM tomorrow (in hope the rom did manage to loose a bit or two) ... hopefully it works out..
It didn't like my loopback wiring, through MAX232 it seems. Too much current and 200mV overvoltage after lifting the Vcc to 5V (Inline diode from odds and ends box did cut only 1.3V ). On the other hand it were satisfactory to read "Hello world" from oscilloscope screen and from stack while it did return there. I wonder when I learn that hackin these kind of equipment should be done with fresh pair of eyes and not middle of the night.
The HW specification in the end of the manual would
Quote:You can also*lmoa!! I have been bullshitted with so many ways with this calculator before bying it, but I still love it. ..unfortunately.
use a serial cable to connect to the RS232 port on the calculator. (This cable is
available as a separate accessory.)
RE: 50g serial port tech. - Help. - Eric Rechlin - 01-06-2017 02:48 AM
I will resume sales of my serial cable before too long. It's just that I have way too many things going on at the present. I'm sorry I don't have any available right now, but last year when I thought I'd made enough to last a long time, one person bought 10 and another person bought 5 and before too long I had nothing left. With previous typical sales of one per 2 weeks or so, that put a big dent in my inventory.
In the last month my biggest focus has been on fixing the hosting of my site. This has taken far longer than I hoped. Right now I've moved it to a new server, which performs better and is saving me money, and I've been in the process of fixing bugs that the moving process has uncovered. I'm very close to having everything transferred over, and once I get everything fully functional I will get back to resuming availability of my most demanded products (namely, the 34s overlays, the 34s calculators, and the 50g serial cables, approximately in that order).
You may have already noticed the biggest improvements. My site is now usable on mobile devices, should load faster in all situations, and has cleaner URLs, better usability for voting/commenting on programs, and more screenshots. These are just a few of the changes I've rolled out in recent months.
RE: 50g serial port tech. - Help. - Vtile - 01-06-2017 10:44 AM
@Eric
Your and mister Wans cable design is fine I'm sure and don't feel sorry atleast for me. I would have gone the same route even if I had yours RS-232 cable in disposal.
For random lurkers/readers: http://commerce.hpcalc.org/serialcable.php
Edit. I must ask btw. Is it that the cable doesn't provide more than Tx, Rx and Ground? So it is still "3-wire" max. without further transformer devices and glue software. If so, it might be worth to consider to give clearly that information in somewhere. Some older devices might need the ie. 4th line while still running under 7 (in DE9, DP9 connector).
PS. I had long rant of HPs lack of overall quality and engineering standards in past decade, but I managed to delete it. Like management deleted the quality inside the HP I assume. I hope that the future is better.
PPS. A bit of information the minimum voltage for Receive line seems to be about 2 volts, propably in 3.3 volt TTL (is it called LVTTL?) specs.
PPPS. I need to ensure now that I weren't dreaming last night.. The CLOSEIO command should drive the Transmit line to zero volts (or near zero) right..???? Since testing with my spare unit (2nd hand) it doesn't react to CLOSEIO command and Transmit line stays up until I shutdown the calculator (RS + ON).
PPPPS. Edit. for the above closeIO question.. If I take as a working hypothesis that my 2nd calculator is behaving correcty I must have been encountered to that Receive (RxD) line turns to sink (pulled down through resistor I assume) when you run the CLOSEIO command. While making loopback connection (RxD&TxD wired together), it drives Transmit line down to near 1.8 volts, which on the scope looks like a zero while using +-20 volts FSD setting.
Now this chapter is speculation unless someone can confirm or deny it.
RE: 50g serial port tech. - Help. - joeres - 01-07-2017 06:47 AM
Hi Eric,
(01-06-2017 02:48 AM)Eric Rechlin Wrote: I will resume sales of my serial cable before too long.
many thanks for the good news. At the moment i use only a wrong home made cable.
Kind regards
Joerg
RE: 50g serial port tech. - Help. - ilkka777 - 05-06-2019 05:22 AM
(01-06-2017 10:44 AM)Vtile Wrote: PPPPS. Edit. for the above closeIO question.. If I take as a working hypothesis that my 2nd calculator is behaving correcty I must have been encountered to that Receive (RxD) line turns to sink (pulled down through resistor I assume) when you run the CLOSEIO command. While making loopback connection (RxD&TxD wired together), it drives Transmit line down to near 1.8 volts, which on the scope looks like a zero while using +-20 volts FSD setting.
Now this chapter is speculation unless someone can confirm or deny it.
Can you remember, how did you solve this? I have similar problem and I dont understand why the HP39GS TX line goes to around 1.6V when connected to pulled down line in arduino