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

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

v0.22, July 11, 2000


Information and installation instructions to accompany pnm2ppa packages for Red Hat Linux available at http://sourceforge.net/projects/pnm2ppa (Updated for pnm2ppa-1.0 and later.) See the "Troubleshooting" section at the end of this document for fixes to some reported problems

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 models, namely

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 come with different bundled Windows software. The 820C and 1000C series are discontinued at this time (January 2000).

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.

Unfortunately, HP only supplies 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 fact, the decline in hardware component prices has meant that the anticipated cost-savings through using host-based PPA instead of printer-based PCL are less than expected, and two of the PPA printer series (820C, 1000C) have been phased out, and replaced by similar PCL printers in HP's product line. The 710C and 720C series are still being sold at this time of writing. All other currently-offered DeskJet models appear to be standard PCL3 printers.

Many Linux users may have inadvertently purchased PPA DeskJet models, mistaking them for PCL3 DeskJets, for which independently-produced Linux drivers have long been available. Fortunately, a reverse engineering effort, started in 1998 by Tim Norman, http://www.normsoft.com/ppa and http://www.httptech.com/ppa, and continued by the pnm2ppa project at http://sourceforge.net/projects/pnm2ppa has managed to produce drivers that provide basic printing functionality for these PPA printers under Linux and other Unices.

The pnm2ppa driver for color printing with PPA printers.

Color printing with PPA printers is currently supported by the (experimental) pnm2ppa driver which is the successor to the stable (but black and white only) driver pbm2ppa-0.8.6 developed by Tim Norman. The pnm2ppa color printing driver is currently (04/2000) essentially finished, and a stable release is imminent.

Currently pnm2ppa can translate 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:

The last two output devices are switches that try to analyse the image, and select an appropriate format; however, they are not recommended for routine use, as they may inconsistently choose the format. The ghostscript-5.10 package supplied with Red Hat 6.x distributions provides all these devices; older versions may not. To see the list of available ghostscript output devices, type the command line
gs --help
if the required ppmraw or pbmraw devices are not shown, you will have to upgrade your version of ghostscript.

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  
(all on a single line). In this example the paper size is explicitly given to gs as US Letter (8.5"x11") size (letter); pnm2ppa no longer needs to be told what the paper size is, and will read it from the gs output (and check that it is a permitted size for the printer type). The pnm2ppa option --eco specifies "EconoFast" mode, for a lower quality output which uses less ink, and prints faster, and -v 720 specifies the PPA printer as belonging to the DeskJet 720C series.

Obviously, it would be impractical to type such a command each time one wished to print something, so in addition to the pnm2ppa driver itself, an enhanced version of Red Hat's rhs-printfilters RPM package is provided; after this is installed, the PPA printer can be managed like other standard printers with the Red Hat printtool utility. The postscript file can then be printed with the simple command

lpr file.ps

Available RPM packages.

Two RPM packages are supplied by the pnm2ppa project for installation on Red Hat Linux systems, and on "compatible" distributions like Mandrake. They can be found at http://sourceforge.net/projects/pnm2ppa. (The latest versions at the time of writing are listed below, but later versions may be available when you read this.)

The second RPM (rhs-printfilters) integrates the PPA drivers with the Red Hat printfilters, used by Red Hat and "Red Hat-compatible" distributions. Do not install the Red Hat RPM on Mandrake systems: use the *mdk.i386.rpm package for Mandrake.

These packages should work on older releases of these distributions, but perhaps may first have to be rebuilt from their source RPMS. For example, to rebuild the pnm2ppa rpm, the command is

rpm --rebuild pnm2ppa-1.0-1.src.rpm
(You must be root to do this, and have the necessary compilers installed; the rebuilt RPM will be created in the directory /usr/src/redhat/RPMS/i386/.)

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

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

To check for this, the command

which pnm2ppa
will find the first instance of pnm2ppa in your path.

Now begin the installation. First install the pnm2ppa RPM:

rpm -Uvh pnm2ppa-1.0-1.i386.rpm
The pnm2ppa executable gets installed in /usr/bin/.

If you are using a 2.2.x kernel, (Red Hat 6.x, Mandrake 6.x, etc.) it 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.) (Note that older (2.0.x) kernels do not have this autoprobe facility.) A script detect_ppa is provided by the pnm2ppa RPM: just type

detect_ppa
to confirm that your Printer is found. If it is not detected, it is possible (especially on Red Hat 6.1) that you will have to add a line
alias parport_lowlevel parport_pc
to the file /etc/conf.modules for the printer to be found (this is a parallel port recognition issue, not specific to PPA printers. and a known "gotcha" on Red Hat 6.1). A typical message from the printer, which will be displayed if autodetection is successful, is:
CLASS:PRINTER;
MODEL:DESKJET 820C;
MANUFACTURER:HEWLETT-PACKARD;
DESCRIPTION:Hewlett-Packard DeskJet 820C;
COMMAND SET:SCP,VLINK;
A list of PPA printers found, and the parallel ports to which they are attached, will also be shown.

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 /dev/lp1 under older 2.0.x kernels, and (usually) /dev/lp0 under newer 2.2.x kernels, as in Red Hat 6.x. Type

test_ppa
and give the details about printer model. papersize, and port number when prompted. You will then be asked which driver (new, pnm2ppa, or old, pbm2ppa) to test, and whether to print a test page, a calibration page, or a color calibration page (for the color driver only).

Installing the PPA-enhanced rhs-printfilters RPM package (if needed).

The rhs-printfilters rpm distributed with Red Hat 6.1 does not support pnm2ppa, and the one distributed with Mandrake 7.0 has out-of-date PPA support. (Later distributions include the support described here). If you use an older distribution, you will first have to replace their rhs-printfilters RPM with the PPA-enhanced version from the pnm2ppa project.

Once you have confirmed you have a working printer, install the RPM rhs-printfilters (either the Red Hat version rhs-printfilters-1.57-4ppa4.i386.rpm or the Mandrake version rhs-printfilters-1.58-4ppa5mdk.i386.rpm) which are PPA-enhanced versions of the packages that comes with Red Hat 6.1 or Mandrake-7.0, respectively:

rpm -Uvh rhs-printfilters-1.57-4ppa4.i386.rpm      (Red Hat 6.1)
or
rpm -Uvh rhs-printfilters-1.58-4ppa5mdk.i386.rpm      (Mandrake 7.0)

Configuring the print filters with printtool.

Now 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
In the 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), as mentioned above. 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

Select the appropriate entry for your printer model. You will then be presented with various options:

When you have made your choices, click on Ok to save your selections and close the "Configure Filter" screen, and then click on OK to close the "Edit Local Printer Entry" screen.

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:

At present, the procedures for fine-tuning these parameters are primitive. Use test_ppa to print the test pages or calibration patterns to adjust the offsets.

If you wish to specify these parameters using the command-line options described above, they can be entered in the "extra GS options" box using the Print System Manager (printtool), as described above.

Utility programs for the printer.

HP's Windows software provides a utility program that sends PPA commands to tell the printer to perform taks like cleaning the printheads, etc. The codes for some of these functions have already been reverse engineered. There are plans 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 (volunteers, anyone?).

Troubleshooting

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

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, ppa.announce (announcements), ppa.users (users helping users) and ppa.devel (developers). You can subscribe to them, or browse their archives, at http://www.httptech.com/ppa.

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).


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