PPA Printer-Support RPM Packages for Red Hat Linux and Compatible Distributions

The pnm2ppa project team ppa-rpms@users.sourceforge.net

Overview of HP's PPA DeskJet Printers.

Most of Hewlett-Packard's DeskJet(tm) printers use the PCL3 command language, and are currently supported by Ghostscript drivers. However, a few legacy models, namely

• DeskJet 710C Series: HP DeskJet 710C, 712C (discontinued)
• DeskJet 720C Series: HP DeskJet 720C, 722C (discontinued)
• DeskJet 820C Series: HP DeskJet 820Cxi, 820Cse (discontinued)
• DeskJet 1000C Series: HP DeskJet 1000Cxi, 1000Cse (discontinued)

feature "Host-based" printing, and use HP's proprietary PPA (Printer Performance Architecture) protocol, instead of PCL. The two models in each series are physically identical; they just came with different bundled Windows software. All PPA printers are now discontinued from HP's product lines, but may still be found as second-hand legacy items.

PPA printers rely on software running on the host CPU to carry out the low-level processing of printer output that would be done by hardware in a standard PCL printer. The relation of PPA printers to PCL printers is analogous to the relation between "Winmodems" and true modems. Presumably, the idea at the time was that this would allow cheaper hardware to be used, but the decline in hardware prices probably meant that the savings were not significant, and PPA printing seems to have been abandoned.

Unfortunately, HP only supplied Windows software drivers for PPA printers, and have indicated that it is unlikely that they will ever make the proprietary PPA specs public. This is apparently because of concerns that publication of the specs might reveal crucial details of HP's trade secrets about "color science" to competitors. (A secondary issue is that it is apparently possible to physically damage the printer by sending it bad sequences of PPA commands, which is not the case for PCL commands, and it seems that HP do not wish to take any responsibility for such damage by encouraging unofficial PPA programming.)

In the past, Linux users often inadvertently purchased PPA DeskJet models, mistaking them for PCL3 DeskJets, which have traditionally been well-supported by Linux drivers. Fortunately, a reverse engineering effort, started in 1998 by Tim Norman, and continued by the pnm2ppa project at http://pnm2ppa.sourceforge.net, and http://sourceforge.net/projects/pnm2ppa has managed to produce drivers that provide basic printing functionality for these PPA printers under Linux and other Unices. While HP have recently begun to release their own Linux drivers for PCL3 DeskJets, they have not included drivers for their legacy PPA printers in this effort.

The pnm2ppa driver has been stable since v1.04, released October 2000, with no known reproducible bugs, except that image printing quality was not so good. This version has been distributed with Red Hat, and other Linux distributions. v1.10, released July 2002, contains a lot of changes that improve image quality, in particular by improved bidirectional printing, and always printing black on top of color.

A better improvement would be for someone to make a PPA backend to gimp-print, using pnm2ppa as a guide for how to send data to PPA printers. But, since PPA printers are now "legacy" hardware, and pnm2ppa appears to work fine for most printing tasks, it is unlikely that any new developers will be interested in doing this, and there is currently no further development anticipated. The project is currently in "low-maintenance mode".

The pnm2ppa driver for color printing with PPA printers.

Color printing with PPA printers is supported by the pnm2ppa driver which is the successor to the older black-and-white-only driver pbm2ppa-0.8.6 developed by Tim Norman.

pnm2ppa translates portable anymap (pnm) format images into a stream of PPA instructions which can be sent to the printer. In the driver name, "pnm" stands for the superset of three image formats: ppm (portable "pixmap" format for color images), pgm (portable "greymap" format for greyscale images), and pbm (portable "bitmap" format for black and white images).

Ghostscript has a number of "output devices" that produce pnm format output from postscript or pdf input. These come in plain (text) and raw (binary) variants. While pnm2ppa can now interpret both plain and raw pnm formats, there is no point in using the inefficient plain formats: always use the "raw" output devices, which are:

• ppmraw - raw pixmap format (color images);
• pgmraw - raw greymap format (greyscale images);
• pbmraw - raw bitmap format (black and white images);
• pnmraw - selects between ppm, pgm, and pbm raw formats;
• pgnmraw - selects between pgm and pbm raw formats.

gs --help

The data must be streamed directly from ghostscript to pnm2ppa to the (local) printer without being stored in any intermediate file: one ppm-format (color) US Letter size page is represented by 3x5100x6600 Bytes (100MB) in binary format and four times this amount in text format.

An example of a command line for printing a postscript file file.ps using gs (ghostscript) and pnm2ppa is

cat file.ps | gs -q -sDEVICE=ppmraw -r600 -sPAPERSIZE=letter -dNOPAUSE \
 -sOutputFile=- - | pnm2ppa --eco -v 720  -i - -o - | lpr -l  

• pnm2ppa expects that the input resolution is 600dpi (or 300dpi if it is called with the pnm2ppa --dpi300 ...option). This corresponds to the gs -r600 ... or gs -r300 ... ghostscript options. If other higher/lower input resolutions are used, the size of the printed image will be larger/smaller, provided it is within the printer's allowed size range.

Obviously, it would be impractical to type such a command each time one wished to print something, and since RedHat 6.2, printfilter support for pnm2ppa is built into Red Hat's printer configuration scheme, so after configuration, the simple command

lpr file.ps

• Also, if you wish to print to paper sizes supported by ghostscript, but not supported by the Red Hat Printer configuration utilities, you can use scripts like the one above. The HP 710C, 720C, and 820C series support paper sizes from 3"x3" to 8.5"x14", while the 1000C supports 4"x6" to 13"x19".

Available RPM packages. A RPM package for pnm2ppa is part of the Red Hat Linux distribution starting with Red Hat 6.2. You will also find a RPM package for the latest release of pnm2ppa at http://sourceforge.net/projects/pnm2ppa.

The latest version at the time of writing is pnm2ppa-1.10-1rh7x.i386.rpm, and is built on Red Hat 7.3, or pnm2ppa-1.10-1rh62.i386.rpm, built on Red Hat 6.2. If you are running a different release of Red Hat (or a different Linux distribution) you may need to download and rebuild the source RPM pnm2ppa-1.10-1.src.rpm instead:

rpm --rebuild pnm2ppa-1.10-1.src.rpm

Red Hat 6.2 and later also includes support for configuring your printer to use pnm2ppa. (Information necessary for configuring pnm2ppa on older Red Hat releases has been removed from this document; for this, see the documentation that came with pnm2ppa-1.04, or update your RedHat distribution.) Note: If you are still using Red Hat 6.2, you may wish to update the print filter support for pnm2ppa that comes with it. The pnm2ppa-1.10-1rh62* RPM package supplies the necessary files that you can use. After installing this RPM, see /usr/lib/rhs/rhs-printfilters/README.ppa for details.

Installing the pnm2ppa RPM package and setting up the PPA printer.

To install the RPM package, you must log in as the system administrator, root.

Now begin the installation. First install the pnm2ppa RPM:

rpm -Uvh pnm2ppa-1.10-1*.i386.rpm

The Linux kernel will be able to autodetect IEEE-1284 devices like PPA printers, provided they are attached to the parallel port with a bidirectional IEEE-1284 cable. (If your printer works under Windows, you have the correct cable.) A script detect_ppa is provided by the pnm2ppa RPM: just type

detect_ppa

CLASS:PRINTER;
MODEL:DESKJET 820C;
MANUFACTURER:HEWLETT-PACKARD;
DESCRIPTION:Hewlett-Packard DeskJet 820C;
COMMAND SET:SCP,VLINK;

At this point it is useful to test that your printer is working, by printing a test page using the supplied script test_ppa which the RPM has installed. You will need to know your printer model (710, 712, 720, 722, 820, 1000), your paper size (letter, legal, a4) and the printer port the printer is attached to. If it is attached to the primary parallel port, this is (usually) /dev/lp0. Type

test_ppa

• Tip: The test_ppa script does not use the Red Hat print filters, so it is useful when troubleshooting, for testing if any printing problems are associated with the basic printer installation, or with the configuration of the print filters.

Configuring the print filters.

Note: Red Hat 7.3 now features either CUPS or LPRng printer management. The configuration tools should be able to configure pnm2ppa, using the information about it taken from the Linux Printer Database. Apart from the addition of a new --dpi300 option to accept 300dpi input (useful for printing PNM output from 300dpi scanners), there have been no changes in the pnm2ppa command line since the pnm2ppa-1.0 release, so the configuration scripts are stable. (They can only use the default 600dpi input mode.)

Since Red Hat 7.1, there is a graphical printer configuration utility printconf-gui. In Red Hat 6.2 and 7.0, the older configuration utility called printtool is used. In either case, start the "Red Hat Linux Print System Manager" (as root) to configure the printer, either by clicking on the printer icon in Red Hat's "control-panel", or just typing

printtool

Configuring the print filters with the Red Hat 6.2/7.0 printtool

(Skip this section unless you are still using Red Hat 6.2 or 7.0)

The following description is for the older printtool that is used by Red Hat 6.2/7.0. The printer configuration utility printconf-gui for Red Hat 7.1 and later is a little different, as it is based on the foomatic printer configuration database which contains entries for pnm2ppa (but not the older pbm2ppa). You should be able to easily figure out what to do: it can configure all pnm2ppa command-line options in the Driver Options screen.

In the Red Hat 6.2/7.0 Print System Manager window, click on Add, then in the "Add a Printer Entry", select Local Printer, and click Ok. Hopefully, the port on which the printer is attached will be listed as "Detected" (if not, fix the problem before continuing, perhaps by adding the line "alias parport_lowlevel parport_pc" to /etc/conf.modules). You will now have to "edit the local printer entry" for the PPA printer. Click on Select to chose the "Input filter". The Configure Filter screen will open. Among the many printer entries in the list "Printer Type", you should find three entries

• HP DeskJet 1000 series (PPA) (for 1000Cse, 1000Cxi models)
• HP DeskJet 710/720 series (PPA) (for 710C, 712C, 720C, 722C models)
• HP DeskJet 820 series (PPA) (for 820Cse, 820Cxi models)

• The Driver Description box contains information about the driver (you may have to use the scrollbar at the right of the box to read it all).
• The resolution box shows a single resolution (600x600). There are no other choices.
• The Paper Size box allows various choices (only letter, legal, and a4 seem correspond to native paper sizes printed by the Red Hat print filters; the other choices, (a3, ledger, ...) appear to get resized by the print filters to print on US Letter size paper (?) ). (Other paper sizes cannot be selected this way, but you can print to any papersize, if it supported by both ghostscript and the printer, using a script, as described above, that bypasses the RedHat printfilters.)
• The Color Depth/ Uniprint Mode box allows various selections of color and print quality (These are achieved by using various combinations of the pnm2ppa options --eco (EconoFast mode), -p (disable black ink cartridge) and --bw (black and white printing only), without direct intervention by the user.) The choices (in the most recent printerdb database) are:
  • Black and White, econofast mode (--bw --eco)
  • Black and White, normal quality (--bw)
  • Color, econofast mode (--eco --fd)
  • Color, normal quality (--eco)
  • Color, high quality
  • Color, normal quality, black ink disabled (-p --eco)
  • Color, high quality, black ink disabled (-p --uni)
  (These are the choices that will be presented by "official" rhs-printfilters-1.72; if you installed a pnm2ppa RPM package from the SourceForge pnm2ppa site, you may have a file /usr/lib/rhs/rhs-printfilters/README.ppa explaining how to modify earlier versions of rhs-printfilters to show these updated choices.) You may also see a choice to use the older "Legacy" driver pbm2ppa (black and white only); this is is stable but unmaintained; it may still be a useful alternative to pnm2ppa on older, slower systems with less available memory.
• The three Printing options are not relevant here, and should not be selected. They are for direct printing of text (ascii) to non-postscript printers, but since the only way of printing text files with pnm2ppa is by first converting them to postscript(tm), this is not possible on the PPA printer.
  • It is important that the choice "Fast text printing (non-PS printers only)" is NOT selected, so that the print filters will convert text files to postscript before printing.
• The Margins entries control the margins used when printing text files (these are instructions to the text-to-postscript conversion process).
• The Extra GS options box is not only a place for adding options for ghostscript, but also for the PPA drivers. Leave this box empty unless you know what you are doing. As explained in the text in the Driver Description box (you did read it, didn't you ?), the entry should be in the format:

   
  gs_options PPA ppa_options 
  

  Anything before the "PPA" is interpreted as a gs option, anything after it is interpreted as a ppa option. You can learn about pnm2ppa options by typing either "man pnm2ppa" or "pnm2ppa --help" at a command line (hopefully, these two sources of information will be consistent with each other!);

You are now back in the "Red Hat Print System Manager" screen; highlight the printer you just configured, and, in the Tests menu, choose Print Postscript test page to print a test page using the Red Hat print filters. If this printed correctly, your print system is set up to use the PPA printer, just like any of the other printers that the Red Hat print filters support.

Configuring pnm2ppa.conf and calibrating the printer.

A number of printer parameters are set to reasonable default values for each of the printer models, but you may wish to "fine tune" or calibrate your printer. The default values can be overridden by entries in the configuration files, which by default are /etc/pnm2ppa.conf and /etc/pbm2ppa.conf. At 600dpi, one pixel is 1/600 inch.

The user-adjustable parameters are:

• verbose 1 and silent 1. These control messages about progress and errors from pnm2ppa. By default, messages are sent to the system log /var/log/messages. The verbose 1 keyword send copies to stderr, the standard error stream to the terminal. The silent 1 keyword silences the stream of messages to the system log.
  • The system log messages may be silenced in the default configuration file; switch off "silent" mode with "silent 0" for debugging printer problems (or use verbose mode).
• The version keyword can be used to specify the printer model as 710, 712, 720, 722, 820, or 1000. It is not needed if you use the RedHat printool to configure the printer.
• xoffset and yoffset: the x-offset and y-offset (in pixels) of the printed image on the page, which should be chosen so the image is correctly centered on the paper. (These can also be set with the -x <xoff> and -y <yoff> options.) See CALIBRATION.html (or CALIBRATION.txt) for more information.
• topmargin, bottommargin, leftmargin, rightmargin: the four margins, which define the distances (in pixels) from the edges of the paper to the printed region; parts of the image that are outside these margins will not be printed. (These can also be set with the -t <top margin> , -b <bottom margin> , -l <left margin> , and -r <right margin> options.)
• ColOffsX and ColOffsY: the x-offset and y-offset (in pixels) between the color image produced by the color ink printer head, and that produced by the black ink printer head. These should be recalibrated each time an ink cartridge is replaced. See CALIBRATION.html (or CALIBRATION.txt) for more information.
• blackshear and colorshear: these are x offsets between right-to-left and left-to-right sweeps of the print head, one for the black printing and one for the color printing. These provide sideways offsets (in pixels) of the right-to-left sweeps, that can be used to correct "shearing" when printing in modes that use bidirectional print head sweeps.
• unimode 1 will make unidirectional print sweeps (left-to-right) the default, instead of bidirectional sweeps. The --uni and --bi options can control how a particular print run is printed. Unidirectional printing is only useful (it is slower) if there are issues of "shearing" in high quality image printing.
• blackness : this takes values 0,1,2,3 or 4 drops of black ink per pixel, and controls black ink density in black-and-white and "text-like" black regions in color printing. At present, this has no effect on printing with the black ink cartridge disabled, or on black regions identified as "image-like". (This can also be set with the -B <n> option, where n is the number of drops.)
• GammaR, GammaG, and GammaB: the are the three "gamma" parameters that define the standard color correction curves for red, green, and blue. Changing these will affect how colors appear (decreasing any Gamma enhaces the corresponding color). The Gamma values are specified as decimal numbers, with Gamma = 1.0 corresponding to no color correction.
• Gamma values can also be specified using integer numbers RedGammaIdx, GreenGammaIdx, BlueGammaIdx; These are determined by a procedure discussed in COLOR.html or COLOR.txt, which involves printing a test page. The papersize keyword specifies the paper size used for this testpage, because it is produced by pnm2ppa without the input that usually specifies the page size.
• The keywords black_ink 0, color_ink 0, cyan_ink 0, magenta_ink 0, and yellow_ink 0 can be used to switch of the various inks; this can be useful in troubleshooting and debugging pnm2ppa.

Use test_ppa to print various test pages or calibration patterns to adjust the offsets.

If you wish to specify these parameters using the command-line options described above, in Red Hat 6.2/7.0 some of them can be entered in the "extra GS options" box using the Print System Manager (printtool), as described above. In Red Hat 7.1 and later, all command-line options can be set using the new printconf-gui utility.

Utility programs for the printer.

HP's Windows software provides a utility program that sends PPA commands to tell the printer to perform tasks like cleaning the printheads, etc.

On Red Hat Linux, You can use test_ppa (which acts as a command-line front-end for calibrate_ppa) to print head-cleaning patterns.

There is a graphical (gtk-based) tool written by Javier Sedano for creating a pnm2ppa.conf file and acting as a front end to calibrate_ppa. This is called ppaSet, and a beta version of it can be found in the same place as the pnm2ppa-1.10 distribution at http://sourceforge.net/projects/pnm2ppa

There was also at one time a proposal to add support for PPA printers to the PUP (Printer Utility Program) utility, which is also a project at http://www.sourceforge.net. However, as of the time of writing, no PUP support for PPA printers is available.

Troubleshooting

The first thing to do is to look at the messages from pnm2ppa in the system log to see what is happening, whether pnm2ppa actually received any input, and if it was valid. (You may need to enable system log messages in /etc/pnm2ppa.conf, see above.) Maybe ghostscript failed to convert your postscript file into PNM format: in that case the system log reports "Fatal Error! Input image (pnm2ppa) is not a PNM image". (note: when this occured, older versions of pnm2ppa reported "Input image is not a supported PNM format" which may have been confusing). This is because the input received by pnm2ppa was not a valid PNM image, but instead ghostscript failed to produce any PNM output at all, and its only output was probably just an error message. This is not a pnm2ppa problem!

Here are suggestions for dealing with other problems that you may encounter.

• Printing fails in the middle of a print run, perhaps when a figure embedded in the document is printing (in the latest pnm2ppa versions, printing finishes normally, but an incomplete document is printed). The system log reports that read_line could not read the image, and found EOF (end-of-file). This probably means that ghostscript's "ppmraw" or "pgmraw" output device started correctly, but failed for some reason before finishing the image conversion from postscript to PNM format, usually leaving a core dump. (This has been seen to happen in ghostscript 5.10 ; upgrading to ghostscript 5.50 solved the problem.) If you cannot upgrade, try printing the document in black-and-white using the ghostscript "pbmraw" output device.
• You printed an image file using a "high quality" printer setting, but it has visible horizontal lines on it and printing under Windows(tm) 9x doesn't show this effect (except in "economode"). These are probably "swath boundaries", showing the junction between different sweeps of the print head. Solution: using unidirectional printing (PPA option --uni, or unimode 1 in /etc/pnm2ppa.conf) helps a little. this problem is fixed in the pnm2ppa-1.10 release
• "Flashing light syndrome ". Your printer usually works, but you have found that some particular documents cause the printer to fail, and the lights on its panel start flashing rapidly in sequence. Solution, turn the printer off and back on again. This is not supposed to happen any more; if it happens reproducibly, contact the pnm2ppa developers, and offer to make the offending file available for testing and diagnosis of this problem. (Don't sent it to the Mailing List unless requested). Bug reports can be filed at the SourceForge pnm2ppa site.
• You wish to print on envelopes or other non-standard media not supported by the print filters? Solution: if you can get Ghostscript (gs) to produce the correct image, and the paper size is in the range allowed by your printer, you should be able to do this with a script that bypasses the print filters, as described earlier in this document.
• Colors look wrong, or do not match what the Windows(tm) 9x driver produces. Solution: check that your color ink cartridge is not running out of some ink color; if not, (a) adjust the "gamma" entries in /etc/pnm2ppa,conf, or (b) install a customized color calibration file /etc/pnm2ppa.gamma. See the file COLOR.html (or COLOR.txt) for more information.

Contacting the pnm2ppa project.

Send comments or corrections (about this document or the RPMS) to: ppa-rpms@users.sourceforge.net

There are three mailing lists, pnm2ppa-announce@lists.sourceforge.net (announcements), pnm2ppa-users@lists.sourceforge.net (users helping users) and pnm2ppa-devel@lists.sourceforge.net (developers). You can subscribe to them, or browse their archives, at http://sourceforge.net/projects/pnm2ppa. (The older pnm2ppa mailing lists died with the ListBot service)

To contact the developers, subscribe to ppa.devel and post a message.

There are Public Forums for posting questions and comments at http://sourceforge.net/projects/pnm2ppa (but whether you get any help from these, depends on whether anyone is reading them (unlikely!)).