A diagnostic and calibration script for the Epson LQ-590II 24-pin impact printer running on Debian or Raspberry Pi OS via CUPS. Prints a one-page sample showing every internal font and pitch combination the printer supports, along with column rulers and a bottom-margin measurement strip.

The LQ-590II has nine font/quality panel selections (USD, HSD, Draft, Roman, Sans Serif, Courier, Prestige, Script, Others) and up to six pitches per font (10, 12, 15, 17, 20 cpi, and PS proportional). This script exercises every supported combination on a single sheet of 9.5 x 11 fanfold continuous paper so the operator can:

• Verify all internal fonts and pitches render correctly
• Compare typeface, weight, and quality of each font visually
• Confirm that ESC/P 2 command transmission through CUPS is intact
• Measure where text lands relative to the top and bottom perforations for margin calibration

Hardware:

• Epson LQ-590II (or compatible 24-pin ESC/P 2 printer)
• 9.5 x 11 inch US fanfold continuous paper loaded on the rear push tractor
• USB connection to the host

Software:

• Debian 12 or Raspberry Pi OS Bookworm
• CUPS with a raw queue named LQ590_text targeting the printer
• Bash (the script is not POSIX sh portable; it relies on bash builtin printf behaviour for octal escape interpretation)

Printer configuration (set once via the front panel):

• Software emulation: ESC/P2
• Page length for rear tractor: 11 inches
• Skip over perforation: Off
• Auto tear off: On (recommended)
• Top-of-form: 1/2 inch below perforation (set via Micro Adjust)

Save the script as /usr/local/bin/24dots and make it executable:

sudo install -m 755 24dots /usr/local/bin/24dots

Or copy and chmod manually:

sudo cp 24dots.v6.sh /usr/local/bin/24dots
sudo chmod +x /usr/local/bin/24dots

The script targets a CUPS queue named "LQ590_text" by default. If the queue is named differently, edit the PRINTER variable near the top of the script.

Ensure paper is loaded on the rear push tractor and the printer is at top-of-form. Run:

24dots

The script prints continuously and does not advance to the next page when finished. Paper is left positioned at the last printed line so the bottom-margin measurement can be taken. Press Tear Off/Bin on the printer (or wait for Auto tear off to fire) to advance the page for tearing.

The printed page contains:

1. A column ruler at 10 cpi marking every 10 columns up to column 80
2. A second column ruler at 20 cpi marking every 10 columns up to column 160 (both rulers should end at the same physical position on the page if the printer is calibrated correctly)
3. A title line identifying the test and paper format
4. Six lines for Roman font (10, 12, 15, 17, 20 cpi, and PS)
5. Six lines for Sans Serif (same pitches)
6. Six lines for Courier (same pitches)
7. Five lines for Prestige (10, 12, 17, 20 cpi, PS -- no 15 cpi)
8. Five lines for Script (same pitches as Prestige)
9. Five lines for Draft mode (10, 12, 15, 17, 20 cpi)
10. A ruler header
11. 18 numbered ruler lines for bottom-margin measurement

Total: 60 lines = 10 inches at 6 LPI. With the 1/2 inch top-of-form offset, the last ruler line lands 1/2 inch above the next perforation, giving symmetric top and bottom margins on standard 11-inch fanfold.

Each printed line should appear in a visibly distinct typeface and pitch. Expected observations:

• Within each font, characters get narrower as cpi increases. 10 cpi is widest, 20 cpi narrowest.
• 15 cpi and 17 cpi look similar but not identical (15 cpi is proportionally wider).
• PS (proportional) shows variable character widths -- 'i' narrower than 'W'.
• Roman is a serif typeface; Sans Serif has no serifs; Courier is monospace with serifs; Prestige is a slab serif; Script is cursive.
• Draft lines print noticeably faster and lighter than LQ lines.

Common anomalies that indicate a configuration issue:

• All pitches within a font appear identical: the printer is collapsing condensed modes (firmware issue or wrong base pitch sequence -- v4 of the script had this problem before v6 corrected it).
• All fonts look like Roman: ESC k commands are not reaching the printer. Check the queue is raw and not filtering.
• Letters appear at the start of lines (e.g. "PRoman 10 cpi"): the ESC byte is being stripped from font/pitch commands. Check shell is bash, not dash.
• "000Roman" or similar numeric prefix: a broken font helper that emits an octal digit string rather than the byte (v3 issue).

The Draft block at the end of the page uses ESC x 0 to enter draft quality. The actual speed within draft mode (Normal Draft, HSD, or USD) is controlled by the printer's panel Font button, not by ESC/P 2 commands.

To compare all three:

1. Set panel Font selection to Draft, run the script, label the output "Normal Draft"
2. Set panel Font to HSD, run again, label "HSD"
3. Set panel Font to USD, run again, label "USD"

The Draft block lines will print in whatever speed is currently selected on the panel.

Commands used by the script:

Font numbers used:

Condensed-mode interaction:

The combinations of base pitch and condensed mode produce the effective pitches:

Each pitch helper in v6 cancels condensed first (DC2), then sets the correct base pitch, and applies condensed where needed. This guarantees five distinct widths regardless of prior state.

• Tested only on Epson LQ-590II. Other 24-pin Epson printers with ESC/P 2 support (LQ-2090II, LQ-590, FX series) may work but font sets and supported pitches differ.
• Assumes a raw CUPS queue named LQ590_text. A filtered queue with a PPD-based driver will rasterise the entire stream and produce different output (typically a coarse bitmap of Helvetica-like text instead of native printer fonts).
• Hardcoded for 9.5 x 11 US fanfold paper at 6 LPI. Other paper sizes or LPI settings require adjusting the ruler widths and ruler line count in the script.
• Assumes 1/2 inch top-of-form offset set via Micro Adjust. Without that, the layout will beoff vertically but still readable.
• Bash-only. Will not run under dash or POSIX sh.

• Epson LQ-590II User's Guide (NPD5799-02 EN)
  • https://files.support.epson.com/pdf/lq590ii/lq590iiug.pdf
• ESC/P 2 reference (pp. 156-157 of the user's guide)
• foomatic-db-compressed-ppds package for the LQ-2550 Foomatic PPD (used for graphical PDF printing through a separate filtered queue)

This project is licensed per file:

• 24dots -- GNU GPL v3 or later
• output.jpg -- Creative Commons Attribution-ShareAlike 4.0
• README.md (this file) -- GNU Free Documentation License 1.3

Full per-file licensing is recorded in COPYING, in the machine-readable Debian copyright format. Licence texts are in the LICENSES/ directory.

Copyright (C) 2026 Dillon Feeney. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the licence is in LICENSES/GFDL-1.3-no-invariants-only.txt.