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
printfbehaviour 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/24dotsOr copy and chmod manually:
sudo cp 24dots.v6.sh /usr/local/bin/24dots
sudo chmod +x /usr/local/bin/24dotsThe 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:
- A column ruler at 10 cpi marking every 10 columns up to column 80
- 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)
- A title line identifying the test and paper format
- Six lines for Roman font (10, 12, 15, 17, 20 cpi, and PS)
- Six lines for Sans Serif (same pitches)
- Six lines for Courier (same pitches)
- Five lines for Prestige (10, 12, 17, 20 cpi, PS -- no 15 cpi)
- Five lines for Script (same pitches as Prestige)
- Five lines for Draft mode (10, 12, 15, 17, 20 cpi)
- A ruler header
- 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:
- Set panel Font selection to Draft, run the script, label the output "Normal Draft"
- Set panel Font to HSD, run again, label "HSD"
- 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:
| Sequence | Bytes | Purpose |
|---|---|---|
| ESC @ | 0x1B 0x40 | Reset printer |
| ESC x 1 | 0x1B 0x78 1 | Select LQ (Letter Quality) mode |
| ESC x 0 | 0x1B 0x78 0 | Select Draft mode |
| ESC k n | 0x1B 0x6B n | Select font n (0..7) |
| DC2 | 0x12 | Cancel condensed mode |
| ESC P | 0x1B 0x50 | Set 10 cpi base pitch |
| ESC M | 0x1B 0x4D | Set 12 cpi base pitch |
| ESC g | 0x1B 0x67 | Set 15 cpi base pitch |
| SI | 0x0F | Apply condensed mode |
| ESC SI | 0x1B 0x0F | Apply condensed mode (alt form) |
| ESC p 1 | 0x1B 0x70 1 | Enable proportional spacing |
| ESC p 0 | 0x1B 0x70 0 | Disable proportional spacing |
Font numbers used:
| n | Font |
|---|---|
| 0 | Roman |
| 1 | Sans Serif |
| 2 | Courier |
| 3 | Prestige |
| 4 | Script |
| 5 | OCR-B |
| 6 | (varies) |
| 7 | Orator |
Condensed-mode interaction:
The combinations of base pitch and condensed mode produce the effective pitches:
| Base | + Condensed | Effective cpi |
|---|---|---|
| 10 | no | 10 |
| 12 | no | 12 |
| 15 | no | 15 |
| 10 | yes (SI) | 17.1 |
| 12 | yes (SI) | 20 |
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.
Remember the '90s? When every office party, bake sale, and surprise leaving-do was announced by a six-foot strip of fanfold paper that took the dot-matrix a full tea break to grind out, tractor holes still attached? This brings that back -- ribbon screech and all.
This script prints a string as a large banner on continuous-feed paper using an
Epson LQ-590II (or any ESC/P 2 printer). The text is rendered with a scalable
font, rotated ninety degrees, and sent as 24-pin bit-image graphics, so each
character is as tall as the printable paper width and the banner runs along the
length of the feed. This is the only way to reach that size: the printer's
built-in fonts scale no larger than about half an inch. It needs Python 3,
Pillow, and NumPy, plus a CUPS queue for the printer. Run it by piping its
output to lp:
python3 banner.py "Your text" | lp -d LQ590_text -o rawReplace LQ590_text with your own queue name; lpstat -p lists them and
lpstat -d shows the default. Ink weight is set with the BANNER_DENSITY
environment variable, which takes a named level -- full, half, light, or
lighter -- or any fraction such as 0.35; lower values thin the dots through
an ordered-dither mask and print faster. Before committing to paper, pass
--preview out.png to write the bitmap to a file instead of printing it. Three
further variables tune the layout: BANNER_WIDTH_IN for the printable width in
inches (default 8.0), BANNER_MARGIN_IN for the blank margin on each side
(default 0.25), and BANNER_FONT for the path to a TrueType or OpenType face
(default DejaVu Sans Bold).
BANNER_DENSITY=0.1 python3 banner.py "Your text" --preview out.pngPrinting helpers (ESC/P + CUPS). Requires $PRINTER to name a valid lp
destination. Source this file from ~/.bashrc (or ~/.profile) to load:
[ -f /path/to/24dots_functions.sh ] && . /path/to/24dots_functions.shBoth functions depend on: fmt, lp (CUPS). 24dots_explicit assumes the
target printer understands ESC/P control codes.
Notes:
Define $PRINTER before or alongside these functions, for example:
export PRINTER=officein the same file or in your environment setup.
After editing the sourced file, reload it with:
. path/to/24dots_functions.shor open a new shell.
Confirm loading with:
declare -F 24dots_panel 24dots_explicitwhich lists the names if defined.
- Epson LQ-590II User's Guide (NPD5799-02 EN)
- ESC/P 2 reference (pp. 156-157 of the user's guide)
- Detailed: EPSON ESC/P Reference Manual
foomatic-db-compressed-ppdspackage for the LQ-2550 Foomatic PPD (used for graphical PDF printing through a separate filtered queue)
This project is licensed per file:
24dotsand24dots_functions.sh-- GNU GPL v3 or lateroutput.jpg-- Creative Commons Attribution-ShareAlike 4.0README.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.