HP48GX - HP49G+ = ? missing


I use an HP-48GX & COGO card to do construction stakeout for a local heavy construction company. I was very disappointed to hear that the 48's have been discontinued without a suitable replacement. The 48's have the ability to communicate with our total-station instruments. But I hear that the 49G+ calculators can not. Can anyone here tell me what the 48GX has, that the 49G+ doesn't, that allows this communication? Would it really have added that much more cost to include it in the 49's? From the beginning, HP has always provided surveyors with the latest and greatest calculators. I can only hope they will continue to serve the surveying industry in the future.


The 48GX calculators have an RS-232 (serial) interface. The 49G+ has only USB (device mode, so it can only talk to a PC or other USB host). The 48GXII has RS-232, but it's really a cut-down version of the 49G+, it runs the OS of the 49G, not the 48G series. The 48GXII also doesn't take plugin cards like the 48GX did.

The 49G+ also has IrDA, so you might be able to use an IrDA to RS-232 adapter.


So don't think you can't find a couple of replacements. If you want dozens, then you may have a problem.




a small correction:

What you call '48GXII' is actually called '48GII'.

The model name given by hp is totally irritating,

because (as you indicated) the 48GII has nothing to do with a real HP-48 .

To George:

Get some spare HP-48GX units as long as they are available.



To convert from USB to RS232 could you use one of these:




Converters such as that are for adding RS-232 capability to a USB
host that lacks it. It may, for example, be ok for
connecting a 48 series, 49G, and possibly a 48gII, to a newer
computer that lacks any RS-232 port.

But does anyone know of a reasonably-priced adapter for adding
RS-232 capability to a USB device, such as the 49g+?




This could make a neat project if anyone is so inclined. There are several ways it could be accomplished (some are more invasive than others). Perhaps the least invasive method would be to make use of its' SD/MMC host port (aka the card slot). I'm not sure if this is within the scope of HPGCC yet but it should be possible to make a device to plug into the slot and write drivers for it on the 49G+.

One of the more invasive and power hungry methods would be to use one of the host controllers (there are 2 onboard). This method would require drivers and surgery.

These are just the first two ideas that come to mind. Unfortunately device-device won't fly... It needs a host in the chain somewhere.

Good luck,


There are indeed potential work-arounds.

Of course a computer that has USB host capabilities could act as a bridge to RS-232.

The Samsung microprocessor package used in the 49g+ does have two UARTs that aren't being used, and if the signals from one of them are accessible, then it could be used for RS-232, although of course a level shifter would also be required. It's occurred to me that the 48gII might use the same PCB; if so, that might show us where the signals are available. Of course, this would require hardware modification.



If I'm not wrong, the Samsung ARM processor that those calculators use are a ball-grid tipe of package. The unused pins are inaccessible unless its PCB design has some spare tracks to use the serial comms.

Best regards,



The 49G+ also has IrDA, so you might be able to use an IrDA
to RS-232 adapter.

Maybe, but note that most of the IrDA to RS-232 adapters on the
market expect to steal power from a PC's COM port and also require
that you install a device driver on the PC. Adapters without these
requirements are available, but are considerably more expensive.

I have an IrDA to COM port adapter, and for some things, it works
fairly well.

However, if I plug it into my USB host to RS-232 adapter instead
of to the PC's built-in COM port, it doesn't seem to get enough
power; the visible red LED still flashes when signals should be
being exchanged, but not as brightly. I guess that the IrDA may be
working, but not well enough to work with the 49g+'s intentionally
crippled IrDA. Maybe it would work with an IrDA compliant device.

The 49g+'s IrDA is supposed to be limited to 10 cm (4 inches) to
satisfy the "educational community", and that does indeed seem to
be about the maximum range to my IrDA/Rs-232 converter.

Like the 49G and 48gII "via wire" connections, the 49g+'s IrDA has
a flow control problem. SRECV can't reliably handle more than 255
bytes in a "chunk" without overrunning the receive buffer. With my
PC under extremely heavy load, some bytes are lost from an XMIT
command. Note that Kermit and Xmodem aren't affected by this.

You have to make sure that an IrDA connection has already been
established before using XMIT or a printing command, otherwise
bytes from the beginning of the transmission until the connection
is established are lost.

The 49g+ (but not the 48gII) can take MMC or SD cards. Anything
that the calculator stores on the card is formatted as a
binary-transferred file. Also note that the 49g+ uses only the
DOS-style "8.3" "short" filenames for the card. If you want to do
Kermit ASCII compatible transfers via the card, see my "49G+ ASCII
on SD" programs at http://www.hpcalc.org/details.php?id=6017
for a work-around.

The comp.sys.hp48 usenet group has much more information about the
48 and 49 series.



Thanks for all the responses. I have purchased a backup, but I'm actually using outdated equipment now. If I understand you, Jonathan, correctly I could probably use the 48gII model to communicate with my total-station if I entered the program thats on the card directly into the calculators memory? I already own a USB to SERIAL adapter as Tom suggested but I thought that there was a sofware issue in the calculator that prevented communication.



Search these forum archives one and two arcives back (archive 14 etc) and you will find a discussion of the "rs232" issues---because the 48GII (what should be called 49gminus) does not have the same type of rs232---it is somewhat disabled, iirc




Specifically, on the 48gII, the signals at the calculator are at
the chip's logic levels; not at RS-232 levels. The level shifter
is built-in to the cable, and "steals" power from other RS-232
signals normally present at a PC's COM port. But if you want to
connect the 48gII to an RS-232 "3-wire" device, it won't work. For
my suggestion of an adapter that I think should work, see the
following comp.sys.hp48

The other issue is that, like the 49G's RS-232 compatible "via
wire" communications, XON/XOFF software flow control is missing.
This doesn't matter for Kermit and Xmodem, but, depending on what
you're trying to connect to, it may for XMIT and the printing
commands, and for SRECV, you can reliably receive chunks only up
to 255 bytes at a time without overrunning the receive buffer.

Note that anything that I write about the 48gII is "second-hand"
information; I'm not about to waste any money on it.




You might be able to successfully connect a 48gII directly to another device (such as another 48gII) that uses 0V and 3.3V for the signals.

But I expect that attempting to connect it directly to a true RS-232 device without a level shifter, such as in the supplied cable, would result in a fried 48gII.



Most, if not all total stations now come with built in data logging software together withmany programs. Why buy an external logger? A friend bought a TDS Recon [for $2000] and he says it works great. And this was a guy who believed in the GX.
His stock equipment now is the hp33S and the TDS Recon.

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