Re: IR Printer Compatibility Message #8 Posted by James M. Prange (Michigan) on 20 Dec 2006, 3:14 p.m., in response to message #7 by Les Wright
You're welcome Les.
Using the printer really doesn't take much learning though; read
through the owner's manual for the printer, and the sections on
printing in the calculator manuals. For the 48/49 models, read up
on the reserved variable PRTPAR and flags -34, -37, and -38.
I highly recommend getting an AC adapter for it if you expect to
use it at a location with AC power available (it doesn't have to
be a genuine HP adapter, and the output can be AC or either
polarity DC, with a fairly high range of voltages), and if you
expect to run it from the battery very much, use NiMH cells (with
a spare set easily available) instead of alkaline cells.
In your case, assuming that you get an 82240B, if you print to it
with your 48G, then remember to switch it off and back on to
restore the Roman 8 character set before printing to it from your
42S.
The reason for the DELAY command on the 48/49 series is that the
calculator can send about 78 bytes per second, which is a lot
faster than the printers can print text, and the printer can only
receive; it can't send any information back to the calculator. The
print speed varies with the battery condition when the AC adapter
isn't used, but at best, is somewhat slower than one 24-character
line per second. The printers have a 200 byte input buffer, so the
48/49 series sends the first 200 bytes in a continuous stream, but
after that, introduce a user-definable delay before sending the
next line to allow the printer to catch up. Similarly, the 28
series have a flag that can be changed to set the delay for using
the printer with just the battery or with an external power source
as well.
On the other hand, printing a full line of column graphics (in
single-width mode) requires receiving 169 bytes, but the time to
print the line is about the same as printing a line of text, so
the printer may have to wait for more data before printing another
line of column graphics.
Note that the delay is also used when printing "Via wire", but
typically there's little danger of overflowing an input buffer in
this situation, so it's usually best to set the delay to 0 for
this. In particular, note that the "screen capture" functions of
the "Connectivity Kits" use the PRLCD command to "print" the
display via wire.
Note that there are alternative printers available from Martel
Instruments, and it looks to me as if these should be able to
print faster than the calculators can send via IR. Some of the
Martel printers can receive via RS-232 as well, which should allow
faster printing with the 48 series and 49G (and 50g, if you add a
level-shifter for the serial port), and some are supposed to be
able to use IrDA, which should be good with the 49g+/50g. Also
note that the input buffer is much larger (6KB on the MCP8830). Of
course with RS-232 or IrDA input available, that makes it more
likely that the printer can be used with devices that you may own
other than HP calculators. The martel printers have more fonts and
print barcodes, and have a higher maximum resolution. The Martel
models MCP8830 and MCP7830 look particularly appealing to me.
The 82240A/B uses a moving 8-element print head to print a column
of dots at a time, as well as the paper transport mechanism to
advance to the next line. The Martel models don't have a moving
print head, instead using a fixed full-width 384-element thin-film
thermal print head to print a single row of dots at a time, using
the paper transport mechanism to advance to the next dot row.
Offhand, it seems to me that this would mean less mechanical wear
and tear, but on the other hand, perhaps a greater chance of a
heating element failing.
But the last that I read, the Martel printers seemed relatively
expensive, and I have no pressing need for another printer, so
I've never actually tried one. But for someone who wants to buy a
printer to use with these HP calculators, I'd advise getting
information on the Martel printers before spending very much on an
HP 82240A/B. For information on the Martel models, visit
http://www.martelinstruments.com/.
Regards, James
|