Using the Serial Port on the HP 50g Graphing Calculator

[HP-MACH]

Hi!, zekelegge:

IMHO, the best configuration for use, what you can check, if necessary, in your case is, is a little programm ... of Claudio Daniel Lapilli ... https://groups.google.com/forum/?fromgroups#!topic/comp.sys.hp48/JXhtA8R7SQA ... In this example, is 1200 baudios.

[Tim_Wessman]

That is only needed for 1200 baud - no other reason.

[BartdB]

Hi,

OK, I will try to cut a long story short and hopefully still be as clear as possible.

There is a big difference between Tiwag's design and the Eric Rechlin / Allen Wan design.

For one, the Eric Rechlin / Allen Wan design has a microcontroller in it and the RS-232 driver IC. Tiwag's design has only the driver chip to provide the RS-232 compatible signals (which also automatically does the inversion of the Tx & Rx lines).

In Tiwag's post there is a mention of some anomalies, V+ is always present and Tx & Rx lines on the 50g are pulled low when the port is closed. This will lead to problems in some circumstances. There are also problems that can lead to missed start bits etc. Also, most modern RS-232 driver IC's have a power down mode, which can be a problem for some devices where the RS-232 uses the controller's line power (e.g. a PC or the 50g) to power their own driver IC's (to provide isolation).

The Eric Rechlin / Allen Wan design attempts to address this so that the serial comms should work in almost all applications.

Unfortunately I currently don't have a compatible program to view Allen Wan's schematic (the Altium that I use at work doesn't read their schematics), so I can't tell what termination has been used on the 3.3v side. I'll try to find a program that can open this.

EDIT: OK, seems Allen Wan used gEDA, I've found the website and will look at installing it and viewing the schematic.

.

[HP-MACH]

Hi!, zekelegge:

For your problem, i'm have, the solution ...

1) Interface w/Cable connection RS232 - 9 pin male to USB (SABRENT 6ft. N° SBT-USC6K) ...

http://www.sabrent.com/support/knowledgebase.php?article=59 or, equivalent.

2) Interface w/Cable connection RS232 - 9 pin male to mini-USB male

3) Null Modem (RS232-female-female).

See the images ...

  

Note: Use the port USB, with COM 3 or, 4.

With this combination, you can use, in HP50G and PC, with USB Driver HP and the software, Conn4x.

[pin224466]

---

@miguel Angel Caporalini wrote:

Hi!, zekelegge:

For your problem, i'm have, the solution ...

1) Interface w/Cable connection RS232 - 9 pin male to USB (SABRENT 6ft. N° SBT-USC6K) ...

http://www.sabrent.com/support/knowledgebase.php?article=59 or, equivalent.

2) Interface w/Cable connection RS232 - 9 pin male to mini-USB male

3) Null Modem (RS232-female-female).

See the images ...

 

Note: Use the port USB, with COM 3 or, 4.

With this combination, you can use, in HP50G and PC, with USB Driver HP and the software, Conn4x.

---

again, this suggestion does not help to solve the OP's stated problem .

the 232 device that the OP has clearly pointed out that he wants to connect to the 50G is not a computer.  It is an autonomous peripheral device. 

The peripheral device does not have a windows based operating system, nor does it have the ability to load, store, and then execute the windows driver software to "configure" the "prolific chip" that resides in the 232 connector.

I thought your suggestion to the OP to connect an RS-232 to the streamsmart 400 was a simple mistake. 

Now I am beginning to wonder

.... maybe less focus on "kudos" might help.

[HP-MACH]

Hi!, zekelegge:

Have you the device, indicated in, the next manual ?. Have you, installed in one PC, with MS-DOS 6.22 and O.S. w/Windows 3.11? ... http://www.thiecom.de/ftp/mfj/mfj-1214pc.pdf

[Ranothil]

Hi Everyone,

I was off for the weekend, but I am back again. As for your questions, I don't have it yet, but I am planning on getting it if it is compatible! If not, then I will get a different one that is slightly cheaper but is reliant upon a modern day computer instead of the MS-DOS operating system. I also don't have an old computer that runs MS-DOS, but if I was going to use it on my Windows 7 computer, I would just use an emulator. I basically just want to make sure I have a chance of it working with the HP50g before I buy it. Otherwise, I can get one cheaper with better performance that connects to my computer. I can't string my antenna coax all the way down to my desktop basement computer, so I would perfer to use the calculator as a portable alternative. By the way, that link does link directly to the manual, so if anyone wants to see it it is there. 🙂 All the calculator will be doing is (I think) telling the device what mode of transmission I will be operating in and displaying the transmitted and recieved characters. That doesn't seem like to hard of a job for a calculator, considering some of the other things that it can do! Thanks for all of your help and consideration! I just want to make sure I have a chance at making this work before I try it 🙂

~Zekelegge~

[HP-MACH]

Hi!, zekelegge:

You can use DOS 6.22 and Windows 7, in the same PC, as a dual option.

Please, see ... http://thpc.info/dual/win7/dualboot_win7+ms-dos622_on_win7.html

[Ranothil]

Yep! I could try that as well. It might be harder to accomplish than an emulator, but it might also work better! I will keep that in mind 🙂 Is there an MS-DOS emulator for the HP 50g? I doubt it, but if there was it might make things a lot easier. The HP 50g actually has a better processer and more RAM than many IBM-PCs running MS-DOS! That is pretty impressive for a calculator! 🙂

~Zekelegge~

[BartdB]

Hi all,

I have looked at the schematic of the Eric/Allen design, and there seems to be little in the way of resistors in the circuit. (It seems the microcontroller is used to force the MAX3221 off when there is no comms detected, to save power when there is no comms and when the calculator is off).

Eric states on his HP-50g serial cable page that it has been tested from 1200 bps to 115.2 kbps.

(See the link on Allen Wan's page).

However, if needed the cable can easily be shortened. The little PCB is in the DB-9 connector casing which is easy to open. The cable side can easily be unsoldered, cut and re-soldered (just make a note which wire goes where :-).

.