HP50g - RS-232 cable

[joeres]

Hi, I am looking for a HP50g RS-232 cable. No order is possible on the websites http://commerce.hpcalc.org/serialcable.php and http://www.samsoncables.com/catalog/prod...rod_ID=391. And http://www.stk4hp.com/ does not deliver to Germany.

Are there other ways to buy a RS-232 cable?

Thanks for help and kind regards.
Joerg

[cyrille de brébisson]

Hello,

I am not aware of any commercial outfit that sells the cables.

The connector is a standard USB connector, but is unfortunately not widely used, which makes it hard to find.
Furthermore, the electronic signals are 'serial', nor RS-232, so you need a converter chip to make it into a true RS-232 if you want to connect it to a PC..

Note that it is not impossible to make (I made one or two a while ago to test it), just hard...

Cyrille

[Martin Hepperle]

(10-11-2016 05:09 AM)cyrille de brébisson Wrote:  ...
Furthermore, the electronic signals are 'serial', nor RS-232, so you need a converter chip to make it into a true RS-232 if you want to connect it to a PC..
...
Cyrille

Cyrille,

those cables mentioned by Joerg had been developed to do the conversion as well as to fix a few problems with the behavior of the serial interface of the 50g.
They include a level converter and some logic in the connector housing, thus they are more than a simple cable.

Martin

[mfleming]

Hi Joerg,

I was able to find a number of these serial adapters from a local electronics retailer (Fry's Electronics) here in the U.S. and bought the one by Sabrent for my HP50. The Sabrent web site is pretty informative and worth a look.

You can also find offerings on eBay, many of which ship directly from China. You will need to distinguish between the ones that provide a simple logic output from the FTDI chip (usually explicitly stated as 0-5V or 0-3.3V) versus the ones that use the old PC voltage standard (+- 6V if memory serves correctly). Most descriptions are frustratingly vague on voltage, but usually the ones with a DB9 connector are the PC compatible ones you need.

Happy shopping,
~ Mark

[joeres]

(10-11-2016 05:09 AM)cyrille de brébisson Wrote:  Hello,
I am not aware of any commercial outfit that sells the cables.
The connector is a standard USB connector, but is unfortunately not widely used, which makes it hard to find.
:
Cyrille

I see, thanks for the info. I think I have found a corresponding connector on amazon (https://www.amazon.de/MUSB-W4P-Hirose-so...P+Plug+USB).

Kind regards
Joerg

[joeres]

(10-11-2016 02:40 PM)mfleming Wrote:  Hi Joerg,
:
You will need to distinguish between the ones that provide a simple logic output from the FTDI chip (usually explicitly stated as 0-5V or 0-3.3V) versus the ones that use the old PC voltage standard (+- 6V if memory serves correctly).
:
Happy shopping,
~ Mark

Hi Mark,
Thanks for the interesting message. I understand you correctly, you have with such an adapter (FTDI chip) your HP50g simply connected to the PC USB port?

My plan was actually to connect the HP50g with the right cable to an RS232 ExpressCard (Notebook).

Thanks and kind regards,
Joerg

[mfleming]

Hi Joerg,

I actually have two cables, the first being the one for the HP48 or 50 serial port. This cable has a DB9 connector at one end for the PC serial port and a molded end for the calculator. If you search for "HP PC Connectivity Kit" on eBay you can still find the HP48 cable. There may be more information about the HP50 serial port connector on the hpcalc.org web site. Good place to check.

It's been a long time since new a PC included a serial port, so the second cable I have (the one I referred to in the previous post) is a USB to PC serial port adapter. If you already have a serial port on you PC, then you would only need the first cable.

As Cyrille mentioned the HP50 has a pretty wonky RS232 implementation, and AFAIK not too many of those DB9 to HP50 serial port cables are around. Most people relied on the USB COM port for communication or used the SD card to transfer files. You could just get the older style SD card that the HP50 uses and transfer programs and data. Those cards are also getting harder to find, but I did buy a few from Amazon last year after picking up a new 50 after it was discontinued.

Hope that helps!
~Mark

[Simone Cerica]

Here it is explained how to build the cable:

http://www.allenwan.com/hpcalcserialcable/

[joeres]

(10-11-2016 08:38 PM)mfleming Wrote:  :
Hope that helps!
~Mark

Hi Mark,
yes, it helps, thanks.

Kind regards
Joerg

[Claudio L.]

(10-10-2016 10:00 AM)joeres Wrote:  Hi, I am looking for a HP50g RS-232 cable. No order is possible on the websites http://commerce.hpcalc.org/serialcable.php and http://www.samsoncables.com/catalog/prod...rod_ID=391. And http://www.stk4hp.com/ does not deliver to Germany.

Are there other ways to buy a RS-232 cable?

Thanks for help and kind regards.
Joerg

I haven't tried, but one of these level shifters should work (they are 2.8V instead of 3.3V though, but I think they should work the same):

http://www.robotshop.com/en/sfe-db9-rs23...hgodorwChA

All you need to do is to buy a USB type A female connector, solder the wires properly and use a standard USB type A cable to usb B mini 4-pin like these ones:

http://www.monoprice.com/category?c_id=1...id=1030308

If you wire it carefully you don't even need a null-modem adapter, you can cross the wires on the female USB connector.

A long while back I built myself a similar level shifter with a MAX232 but I don't see why these ready-made solutions wouldn't work. Once I soldered the wires and the connector, I made a plastic mold and filled it with a hot-glue gun. In the end I have a "brick" adapter with a USB female A connector that I can use with any cable. It worked very well for years.

[joeres]

(10-12-2016 02:38 AM)Claudio L. Wrote:  I haven't tried, but one of these level shifters should work (they are 2.8V instead of 3.3V though, but I think they should work the same):
:
If you wire it carefully you don't even need a null-modem adapter, you can cross the wires on the female USB connector.

Thank you, sounds very interesting. I think, I will try it.
kind regards
Joerg

[cyrille de brébisson]

Hello,

(10-11-2016 08:38 PM)mfleming Wrote:  As Cyrille mentioned the HP50 has a pretty wonky RS232 implementation
~Mark

Actually, the 50G does NOT have a RS-232 port. It has a serial port which is standard on pretty much all CPU these days.
As it turns out, the signal used by these serial port has exactly the same 'shape' as an old RS-232 (how strange :-) but uses positive logic and CPU voltages (0 to whatever GPIO voltage the chip is using)...

These types of serial ports were/are designed to let CPU communicate with each others easely, cheaply and with minimum silicone. I assume that they were designed using the same signal as RS232 because that was a singal shape that was working (and proven to do it)...

They just did not include voltage boosts (and negative logic) because it would have been expansive to place on chip.

Cyrille

[Garth Wilson]

Quote:Actually, the 50G does NOT have a RS-232 port. It has a serial port which is standard on pretty much all CPU these days.

RS-232 (later called EIA-232, and most lately, TIA-232-F) has been contorted in all kinds of variants, but I keep seeing "TTL-level RS-232" on many forums. That's an oxymoron, but refers to the asynchronous nature (ie, that the receiver must run its own clock, started by the received start bit's leading edge), and the order and timing of the bits. The TTL levels could just as easily be connected to RS-422 or RS-485 line drivers and receivers. "Serial port" usually refers to this common asynchronous signaling method; but there are synchronous-serial ports too which are totally incompatible. SPI and I²C are quite popular for interfacing ICs, but usually are not run long distances like RS-232 can be. Contrary to urban legend, RS-232 can go many hundreds of feet. A friend writes, "I know from application experience that 115.2Kbps is readily achievable on CAT5 UTP cable over a distance of 325 feet." RS-422 and -485 can go at least 90kbps at 3/4 mile.

[joeres]

(10-12-2016 06:47 AM)cyrille de brébisson Wrote:  Hello,

(10-11-2016 08:38 PM)mfleming Wrote:  As Cyrille mentioned the HP50 has a pretty wonky RS232 implementation
~Mark

Actually, the 50G does NOT have a RS-232 port. It has a serial port which is standard on pretty much all CPU these days.
:
They just did not include voltage boosts (and negative logic) because it would have been expansive to place on chip.

Cyrille

Hi Cyrille, Thanks for the explanations. Would not it be the simplest solution to use such a "USB to TTL Serial" module (e.g., https://www.sparkfun.com/products/9873)? USB port is connected to the notebook and the TTL serial port of the module is connected to the 50g.

Sorry for the one more question.
kind regards
Joerg

[Claudio L.]

(10-12-2016 08:42 AM)joeres Wrote:  Would not it be the simplest solution to use such a "USB to TTL Serial" module (e.g., https://www.sparkfun.com/products/9873)? USB port is connected to the notebook and the TTL serial port of the module is connected to the 50g.

Sorry for the one more question.
kind regards
Joerg

If all you want is to connect to a PC, the USB to TTL serial is your best choice. If you want to connect with other RS-232 devices, then you need the level shifter. Finally, if you want to connect with other devices that can't provide power for the shifter, the cable from hpcalc.org's Eric was the only solution I know of that draws power from the calculator side to function. All others draw power from the other side (always assumed to be a PC).

[joeres]

(10-12-2016 01:38 PM)Claudio L. Wrote:  If all you want is to connect to a PC, the USB to TTL serial is your best choice. If you want to connect with other RS-232 devices, then you need the level shifter.

Hi Claudio,
Thanks for the explanations. For the first little project, we need a connection only to the PC. Maybe later we would like to connect an old GPS device to the 50g. As far as this is now clear to me.

(10-12-2016 01:38 PM)Claudio L. Wrote:  Finally, if you want to connect with other devices that can't provide power for the shifter, the cable from hpcalc.org's Eric was the only solution I know of that draws power from the calculator side to function. All others draw power from the other side (always assumed to be a PC).

But can you explain to me, why the level shifter can not simply supply with the power from the 50g?

Thank you and best regards,
Joerg

[Claudio L.]

(10-12-2016 03:12 PM)joeres Wrote:  But can you explain to me, why the level shifter can not simply supply with the power from the 50g?

Thank you and best regards,
Joerg

I meant those ready-made circuits you can buy at sparkfun, etc. are wired to take power from the PC side. You'd have to modify them to get power from the calc, I have no idea how easy (or not) could that be as I haven't had one of them in my hands. I think the old MAX232 needs 5V (not sure, as I haven't used it in almost 10 years), I can't recall if the calc supplies 5V or 3.3V on the serial port. That info should be on comp.sys.hp48 if you dig a little.
Powering from the calc was not trivial, I vaguely recall reading discussions at comp.sys.hp48 about problems when the calc powered off.

[joeres]

(10-12-2016 07:39 PM)Claudio L. Wrote:  I meant those ready-made circuits you can buy at sparkfun, etc. are wired to take power from the PC side. You'd have to modify them to get power from the calc, I have no idea how easy (or not) could that be as I haven't had one of them in my hands. I think the old MAX232 needs 5V (not sure, as I haven't used it in almost 10 years), I can't recall if the calc supplies 5V or 3.3V on the serial port. That info should be on comp.sys.hp48 if you dig a little.
Powering from the calc was not trivial, I vaguely recall reading discussions at comp.sys.hp48 about problems when the calc powered off.

Hi Claudio,
Thanks for all the information.
I'll try it.

Kind regards,
Joerg

[ilkka777]

(10-12-2016 06:47 AM)cyrille de brébisson Wrote:  Hello,

(10-11-2016 08:38 PM)mfleming Wrote:  As Cyrille mentioned the HP50 has a pretty wonky RS232 implementation
~Mark

Actually, the 50G does NOT have a RS-232 port. It has a serial port which is standard on pretty much all CPU these days.
As it turns out, the signal used by these serial port has exactly the same 'shape' as an old RS-232 (how strange :-) but uses positive logic and CPU voltages (0 to whatever GPIO voltage the chip is using)...

These types of serial ports were/are designed to let CPU communicate with each others easely, cheaply and with minimum silicone. I assume that they were designed using the same signal as RS232 because that was a singal shape that was working (and proven to do it)...

They just did not include voltage boosts (and negative logic) because it would have been expansive to place on chip.

Cyrille

I know its old post, but can you clarify what you mean by signal shapes? are you referring to rs-232? im puzzling to find out how serial port of 39gs (same as 50g) works.

[cyrille de brébisson]

Hello,

rs232 is negative logic: signal0 means logical 1 and vice-versa.
rs232 signal levels are in the +/-3~15V range.

However, although modern CPU DO generate "serial" output with the same "shape" as rs232 did, the logic is positive and the signal level are typically in the 0-3.3V range (with 0= logical 0 and 3.3V= logical 1).

Hence the need for signal convertors.

Luckily enough, with Arduino, it is very easy to find such convertors at a low price.
https://www.amazon.fr/Sumind-D%C3%A9boga...way&sr=8-7

Cyrille