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Evolution of the HP 48gII
10-13-2020, 01:37 PM
Post: #1
Evolution of the HP 48gII
How many variants of the HP 48gII were there?

The information here doesn't seem to be entirely accurate. Quoting that page:

Quote:The original 2003 version had 128 KiB RAM and ran on 3 AAA batteries, whereas the second 2007 version (based on the Apple V2 platform) needs four AAA batteries and comes with 256 KiB RAM, added a USB (Mini-B) port and features a better keyboard.

This looks like the original version had no USB port. I have one of which the serial number starts with CNA 4330, which looks like week 33 of 2004, so it's the early version, which is borne out by the horrible keyboard, 3× AAA batteries and 128KB of RAM. But it has a USB port... Did the 48gII have that right from day dot?

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10-13-2020, 01:57 PM
Post: #2
RE: Evolution of the HP 48gII
The original 48gII had a port that looked like a USB port but was actually a serial port that needed a special cable (USB mini-B on one end, DE-9 on the other end) to operate. However, something about it wasn't quite "normal" (I can't remember if it depended on the device connecting to it to provide power to run the serial port, or if its voltages weren't quite right, or what) which made it somewhat useless for the intended purpose of connecting to serial devices, so it really was only good for connecting to a PC.

For the second iteration of the 48gII, it adopted the 50g approach, with the mini-B connector now being a USB port, and a new port (basically a semi-proprietary version of the mini-B port that was seen in some digital cameras around the turn of the millennium) that provided a serial signal (and once again needed a special cable, but a different special cable).
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10-13-2020, 02:09 PM
Post: #3
RE: Evolution of the HP 48gII
Thanks for the clarification, Eric.

How dumb is that, a serial port that looks just like a USB mini-B port? I wonder if it could be damaged by plugging it into a computer using a standard miniUSB cable...

As for the oddity preventing it from running as a real RS-232 port, the odds are indeed that it uses the "wrong" voltages. Probably 0v-3V instead of ±12V so it probably works fine either with a TTL level adapter or with a FTDI or similar USB/Serial adapter. I know that the HP 48 serial port works fine with one of those.

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10-13-2020, 02:51 PM
Post: #4
RE: Evolution of the HP 48gII
It's been too many years so my memory may be wrong, but I think it may have been a combination of the two. The port probably put out TTL voltages, and the special cable had a level shifter in it, but the level shifter needed power from the remote device to run, meaning anything that didn't provide power wouldn't be able to interface with the 48gII.

Contrast that to the serial connector on the later 48gII and 50g, which provided its own power to run a level shifter in the cable.
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