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+--- Thread: HP7475 Plotter with HP48 (/thread-21184.html)
HP7475 Plotter with HP48 - Hiwi - 01-19-2024 08:51 AM
Hi,
i have recently purchased a HP7475- OPT 001 Plotter with serial interface for little money. The plotter did not work, the power supply was short-circuited but this was easy to fix, because it is simple linear regulated circuit with standard parts.
The pen carussel was not moving, There is a plastic connection rod on the stepper motor which broke in thousand pieces. The material became brittle over years.
I made a new one with my CNC milling machine of fiberglass plastic. May be there is a better solution with a 3D printer.
At least the plotter came back to life.
I was inspired from a video back to 2018 on a HP calculator conference, where it was demonstrated connected to a HP48!
This was working out of the box, but only with simple instructions until buffer overrun! (up to 1024 Bytes)
In the manual there are examples for implementation a softwarebase handshaking.
This could be easily made, because you can poll the free buffer size or let the plotter send a free configurable character if the buffer gets full (at any size!)
But the HP48 supports XON/OFF protocol, so it should be possible to get it working with larger plotter file. The trick is to configure the plotter to use XON/XOFF protocol.
This works with ESC.N;19: and ESC.I81;;17:
I was now able to send e.g. the 25kB columbia HPGL file without any problems.
Ralf
[attachment=13204]
RE: HP7475 Plotter with HP48 - TomC - 01-21-2024 02:23 PM
Very nice!
Can you share the files please?
Thank you,
TomC
RE: HP7475 Plotter with HP48 - Hiwi - 01-22-2024 11:45 AM
Hi TomC,
i have attached the HPGL File with HP48 text prefix.
I dont know whether it works on a standard HP48G. I have a 1MB diy built in memory extension in my 48G.
You have to configure the plotter to support XON/XOFF protocol with ESCAPE sequence N and I. (see my last post)
This is necessary for the HP48 as well:
Edit the VAR / LIST IOPAR and change the 4th paramater from 0 to 1.
Now load the HPGL file from PC to the HP48 using hpcomm or kermit.
RCL the string and press XMIT from the IO/SERIAL menu.
If the transfer stops before end with a "0" then DROP and press XMIT again.
If all was successful a "1" is pushed on the stack.
Ralf
[attachment=13213]
RE: HP7475 Plotter with HP48 - TomC - 01-22-2024 02:49 PM
Thank you Ralf!
TomC