sharp-splc-macos

Print from macOS to Sharp AR-2221R / 2421R / 2821R / 3121R — the printers that only speak SPLC, for which Sharp ships a Windows-only driver.

There is no Mac driver for these machines, and there cannot be one made of standard parts: the printer has no PDF, PCL or PostScript interpreter unless you buy the AR-PB10 / MX-PK10 options. What it does have, built in, is SPLC (Sharp Printer Language with Compression).

This project generates SPLC on the Mac: PDF → 600 dpi 1-bit raster → QM arithmetic coding (JBIG1 / ITU-T T.82) → SPLC frames → TCP port 9100.

Verified on	SHARP AR-2221R, macOS 14, real paper out of the tray
Language	Python 3 (no Xcode, no compiled dependencies)
Integration	CUPS backend + a small user-level agent
License	MIT (code), CC BY 4.0 (docs)

The one rule that matters: a page counter incrementing does not mean the page printed. This printer happily accepts a job it cannot interpret, prints an error page, and still counts it. Always verify at the output tray.

---

Why a background agent

macOS runs CUPS backends in a sandbox as _lp: the backend cannot read your home directory, cannot write to /tmp, and cannot import your Python packages. So the backend is deliberately thin — it forwards the spool file over loopback TCP to a LaunchAgent running as you, which does the rendering and talks to the printer.

lp / Preview / any app
        │  PDF
        ▼
CUPS  ──►  /usr/libexec/cups/backend/splcprint   (root, sandboxed, does nothing but forward)
        │  TCP 127.0.0.1:9123
        ▼
agent.py (LaunchAgent, your user)
        │  render → 1bpp → QM encode → SPLC frames
        ▼
printer:9100

Requirements

Item	Notes
macOS 12+	tested on 14.x
Python 3	/usr/bin/python3 is enough; only the standard library is used
Printer reachable over TCP 9100	check with nc -z <printer-ip> 9100
band1.bin	7104-byte static resource, extracted from Sharp's own driver — see below

Install

git clone https://github.com/ufoddqq/sharp-splc-macos.git
cd sharp-splc-macos

# 1. get the static resource out of the Windows driver you downloaded from Sharp
python3 tools/extract-band1.py /path/to/sd3bnp2.dat -o band1.bin
#    expected: 7104 bytes, md5 b7404defe761cfd368aa7f2821ba4557

# 2. install (asks for sudo once, for the CUPS backend)
./install.sh 192.168.1.50 --queue

band1.bin is vendor data and is not redistributed here. If your driver file has a different layout, python3 tools/extract-band1.py <file> --list prints every SPLC frame with its subtype, size and md5.

Test

python3 "$HOME/Library/Application Support/splcprint/splc.py" --pattern test --send 192.168.1.50

This prints a calibration page. It really uses paper — put a sheet in the tray first.

Then a real document:

lp -d SHARP_SPLC file.pdf
lp -d SHARP_SPLC -o fit=exact -o tone=photo photo.jpg

Options

CUPS option	Values	Meaning
fit	auto (default), fit, exact	auto: 1:1 if the ink fits the printable canvas, otherwise scale down. fit: always scale. exact: force 1:1, crop the overflow
tone	text (default), photo	text: hard threshold, solid strokes. photo: Floyd–Steinberg dithering
thresh	1–254, default 200	threshold for tone=text; lower = thinner strokes
copies	1–99	hardware copies

Printable canvas is 4696 × 6382 px at 600 dpi (198.8 × 270.2 mm), slightly smaller than A4, so auto usually trims the white margin instead of shrinking the content.

What works, what does not

	Status
Single-sided text/table printing	works
Photos (tone=photo)	works, dithered 1-bit
Multiple copies	works (passed to the printer as a hardware copy count)
Duplex	the flag is sent (j=1 in the setup string); not validated on every model — try one sheet
Non-A4 paper sizes	not exposed as an option
Scanning	included: scan/ runs an FTP receiver on the Mac (see below)

Scanning (printer → Mac)

Scanning is a completely different mechanism: the printer pushes the image, so the Mac only has to offer an FTP destination. No custom encoder involved.

sudo ./scan/install-scan.sh                        # ~/Scans, random password, printed for you
sudo ./scan/install-scan.sh --dir /Volumes/Data/Scans --password 'something-long'
sudo ./scan/install-scan.sh --uninstall

It installs /Library/LaunchDaemons/com.sharp.scanreceiver.plist (port 21 needs root), starts the receiver, and prints the exact values to type on the printer panel. Received PDFs are normalised to A4 in place by rewriting only the MediaBox and wrapping the content in a scale matrix — images are never re-encoded, and a second pass leaves an A4 file untouched.

Panel side, in short: press CA to leave nEt, then Scan and a number key 1–5. Key 6 is Sharpdesk, which waits for a Windows client that will never arrive — that is the nEt people get stuck on. Details in docs/scan-to-mac.md.

Plain FTP, no TLS. Keep it on a trusted LAN, and set a real password.

Repository layout

splc.py                    SPLC encoder: frames, QM arithmetic coding, raster geometry
print_job.py               PDF → raster → SPLC; also usable as a CLI
agent.py                   loopback service (127.0.0.1:9123) that renders and sends
backend/splcprint          CUPS backend, forwards the spool file to the agent
install.sh                 installer / uninstaller
tools/extract-band1.py     pulls the vendor static resource out of a Sharp driver
scan/scan_receiver.py      FTP receiver (stdlib only); login + upload, no delete/rename
scan/a4_normalize.py       A4 normalisation via PDF incremental update
scan/install-scan.sh       installs the receiver as a LaunchDaemon on port 21
docs/findings.md           how we know the printer cannot print PDF/PCL/PS
docs/scan-to-mac.md        the scan direction in detail

Why this is not a "crack"

SPLC is the printer's standard language. PCL6 and PostScript3 are the paid options (AR-PB10, MX-PK10); the Mac driver Sharp offers requires both. This project does not unlock anything — it generates the language the machine already speaks, so no optional kit is needed.

The QM arithmetic coder is implemented from the public JBIG1 (ITU-T T.82) specification. The frame structure and geometry constants were derived from the open-source Swift project below and cross-checked against Sharp's Windows driver.

Credits

Project	What
zy2n9nzt5b-hue/SharpSPLCBridge	Swift SPLC implementation for AR-5516N; protocol structure and geometry reference

License

Code: MIT. Documentation: CC BY 4.0. band1.bin is not covered by either — it is Sharp's data, obtained from your own driver copy.