Re: [hpoj-devel] patch to improve scan speed/robustness

[<pa...@rc...>]

Hi, Joe.

> <...> I tried it again, and sure enough,
> > the original xojpanel didn't scroll and the new one does, meaning that as
> > you said, the peripheral reports the whole string, even on the 570.
> I got the same impression originally. I remembered seeing something scroll,
> but it must have been text scrolling in the titlebar, which is only a little
> smaller than the original xojpanel app itself. 
That makes sense.

> The 600 doesn't have a battery. I checked again, and found hat its clock will
> keep running as long as the printer remains connected to ac power. Some data
> is retained by the printer even if it's disconnected from ac power, but the
> clock is apparently designed to be synchronized with the computer's clock, so
> it gets set by software on the computer. The problem is that I turn the whole
> system on and off with the switch on a surge suppressor.  It's a bit easier to
> hit one switch than three or more. Many people probably turn their system on and
> off this way. It works well under windows, because the software sets up the
> printer automatically when both are started together. If the "hpoj driver"
> could set up the printer automatically, it would be ideal.
OK, this is good to know.  I'll make a note of this.  Ultimately perhaps
this should be handled by the "xojpanel on steroids" we talked about earlier.

> I didn't spend much time trying "hpo set", but all I got from it was "Sorry, set
> not yet implemented."
Oh, I hadn't noticed that until now.  I'm currently rewriting the PML
functionality, and I'll make sure that this gets implemented there.

> Whitespace is now stripped from the trailing end of all messages coming
> from the printer. I found that some of the messages contain control characters
> in addition to spaces.  The negative of isgraph()  is used to filter them out,
> which  will work for all versions of Qt.  
Which messages contain control characters?

> Are there any OfficeJets that output unicode to their LCD?
PML has a provision for strings to be gotten/set in various symbol sets,
including 16-bit Unicode.  I don't know if there are any peripherals which
actually implement Unicode, however.

> Thanks very much. Starting a second copy of xojpanel still causes the
> first copy to freeze, though. xojpanel doesn't call PMLClose() until just
> before exiting, which may be part of the problem.
That's most likely the fault of the lower-level code.  In order to support
multiple instances of xojpanel or other PML clients, there needs to be a
mechanism for multiplexing PML requests from different clients and routing
the replies correctly.  Currently, starting up a second PML client attempts
to open a second PML connection to the peripheral.  ieee12844.c either doesn't
properly handle the peripheral's refusal of the second open, and/or it doesn't
properly handle multiple simultaneous opens period.  The latter is likely
because I've gotten into trouble before while playing around with the scan
and echo channels at the same time.

> I'm not familiar enough with
> system programming to mess around very much with that. The original
> xojpanel code for retrieving the LCD messages is still there. I know what it
> does, but not how it operates. You might want to take a look at the old code
> to see if I've used it correctly. 
OK, I'll take a look at it.  I'll probably hack that area some later anyway
once I finish the new PML interface.

David