Brother DCP-T230 — native macOS driver

A tiny open-source CUPS driver for the Brother DCP-T230 inkjet that runs natively on macOS (Intel and Apple Silicon) without any Linux binaries, VMs, or Rosetta. Scanning is covered too — see scanner/.

Brother's official driver ships only as x86_64 / i686 Linux ELF executables, which will not run on macOS. Fortunately the printer itself speaks a standard protocol — PJL wrapping a PWG Raster stream — so macOS's built-in CUPS filter chain already produces 95 % of what the printer needs. The only thing missing was the thin PJL envelope that tells the printer "here comes PWG raster data". That envelope is what this driver provides.

Files

Scanner

A separate, self-contained native scanner driver lives in scanner/: a Python 3 USB driver (t230scan.py), a tiny progressive-JPEG web UI (t230web.py), and the C reference implementation that documents the reverse-engineered protocol. It runs in user space and is not touched by install.sh in this directory. See scanner/README.md for usage and the wire-protocol summary.

Filter chain

CUPS on macOS does the hard work; our filter just prepends/appends PJL:

PDF ──► pdftopdf ──► cgpdftoraster ──► rastertopwg ──► brother_dcpt230_pjl ──► USB
                     (Apple)           (CUPS)         (this driver)

Output of brother_dcpt230_pjl:

ESC%-12345X                             ← UEL start
@PJL JOB NAME="..."
@PJL SET STRINGCODESET=UTF8
@PJL SET USERNAME="..."
@PJL SET JOBNAME="..."
@PJL SET LOGINUSER="..."
@PJL JOBSETTINGLOG DRIVER="macos-native-1.0"
@PJL SET PAPER=<LETTER|A4|…>
@PJL SET BORDERLESS=<ON|OFF>
@PJL SET JT{TOP|LEFT|RIGHT|BOT}MARGIN=<0|300>  ← 1/1200" units
@PJL SET RENDERMODE=<COLOR|GRAYSCALE>
@PJL SET PRINTQUALITY=<DRAFT|NORMAL|HIGH>
@PJL SET DUPLEX=OFF
@PJL SET MEDIATYPE=<REGULAR|GLOSSY|INKJET|…>
@PJL SET SOURCETRAY=AUTO
@PJL SET MANUALFEED=OFF
@PJL SET FIDELITY=TRUE
@PJL ENTER LANGUAGE=PWGRASTER
<PWG Raster stream: 4-byte "RaS2" + 1796-byte page header + pixels…>
@PJL EOJ NAME="..."
ESC%-12345X                             ← UEL end

This was reconstructed by reverse engineering the closed-source brdcpt230filter Linux binary shipped by Brother:

• The literal @PJL … strings, the RaS2 sync word, and the @PJL ENTER LANGUAGE=PWGRASTER terminator all live verbatim in the binary's .rodata.
• The PWG Raster page-header builder at address 0x4050c4 was disassembled and every field write was mapped to a field in the standard PWG Raster v2 header (HWResolution, cupsWidth, cupsColorSpace=19 (sRGB) / 18 (sGray), cupsNumColors, …). The buffer size passed to the writer was exactly 0x704 = 1796 bytes — the canonical PWG v2 page header size.

No part of Brother's binary is needed at runtime.

Installation

cd macos-driver
sudo ./install.sh

The installer will:

1. Copy brother_dcpt230_pjl into /Library/Printers/Brother/DCP-T230/ and symlink it into the CUPS filter directory (/usr/libexec/cups/filter/ if writable, otherwise /usr/local/libexec/cups/filter/).
2. Install Brother-DCP-T230.ppd.gz under /Library/Printers/PPDs/Contents/Resources/.
3. Try to auto-detect the printer over USB and offer to create a CUPS queue named DCP_T230 for you.

If the auto-detect step skips your printer, add it manually from System Settings → Printers & Scanners → Add Printer and pick “Brother DCP-T230 (PWG/PJL native)” from the driver list.

Manual queue creation (no GUI)

# Find the device URI
lpinfo -v | grep -i dcp-?t230

# Create the queue
sudo lpadmin -p DCP_T230 -E \
    -v "usb://Brother/DCP-T230?serial=XXXXXXXX" \
    -P /Library/Printers/PPDs/Contents/Resources/Brother-DCP-T230.ppd.gz
sudo cupsenable DCP_T230
sudo cupsaccept DCP_T230

Testing

# Simple test print
lp -d DCP_T230 /System/Library/Fonts/Supplemental/Times\ New\ Roman.ttf

# Or a PDF with options:
lp -d DCP_T230 -o media=A4 -o BRResolution=Fine -o BRMediaType=Inkjet mydoc.pdf

Inspecting what's really going to the printer

If you want to verify the PJL envelope without burning paper, redirect the queue to a file:

sudo lpadmin -p DCP_T230 -v file:///tmp/out.prn \
    -P /Library/Printers/PPDs/Contents/Resources/Brother-DCP-T230.ppd.gz
sudo chmod 0666 /tmp/out.prn   # or adjust /etc/cups/cups-files.conf: FileDevice yes
lp -d DCP_T230 mydoc.pdf
head -c 4096 /tmp/out.prn | xxd | head -80

You should see ESC%-12345X@PJL JOB NAME=…@PJL ENTER LANGUAGE=PWGRASTER\nRaS2….

Enable file:// URIs

By default CUPS refuses file:// device URIs. To enable for testing, add to /etc/cups/cups-files.conf:

FileDevice yes

then sudo launchctl kickstart -k system/org.cups.cupsd.

Supported options

Troubleshooting

• Job sits in queue forever / paused with “filter failed”. Check /var/log/cups/error_log for lines tagged brother_dcpt230_pjl. The filter logs options, PWG page geometry, and byte counts at DEBUG/INFO level.
• Page comes out blank or garbled. Redirect to file:// (see above), then run xxd /tmp/out.prn | head -40 and verify the first line starts with 1b25 2d31 3233 3435 5840 504a 4c (ESC%-12345X@PJL).
• macOS doesn't show the driver in the picker. sudo launchctl kickstart -k system/org.cups.cupsd, then reopen the Printers & Scanners sheet.
• SIP blocks /usr/libexec/cups/filter/. The installer falls back to /usr/local/libexec/cups/filter/ which CUPS also searches. Create it first with sudo mkdir -p /usr/local/libexec/cups/filter if needed.

Uninstall

sudo ./uninstall.sh
# then remove the queue
sudo lpadmin -x DCP_T230

Caveats & limitations

• Compression. rastertopwg emits PWG Raster with PackBits compression by default. The reverse-engineered PWG header writer in Brother's binary doesn't explicitly set cupsCompression, and Brother's own printers generally accept both compressed and uncompressed PWG Raster, so this should "just work". If you see garbled pages, try forcing uncompressed output by adding *cupsRasterVersion: 3 and *cupsBitsPerColor: 8 hints to the PPD, or feed uncompressed raster via a foomatic-rip-style wrapper.
• Resolution. Brother's binary hard-codes 300 DPI in the PWG header (HWResolution = 300, 300). This driver relies on rastertopwg to populate the real resolution from the PPD's DefaultResolution: 300dpi. Setting Fine in the PPD raises the PJL quality but not the raster DPI; this matches Brother's own driver behavior.
• No duplex, no Hagaki, no color-matching knobs. Exposed set is deliberately minimal. Extending it is straightforward — add the keyword to the PPD and a mapping row in one of the dict tables at the top of brother_dcpt230_pjl.
• Untested on every page size. Letter, A4, and Photo 4x6 are the most exercised. Exotic sizes may need their PJL PAPER= name tweaked; all the ones I could extract from the binary's string table are mapped, but a few are guesses.

License

The Brother-supplied Linux driver this work was derived from is released under the GNU GPL v2. Any materials here that qualify as derivative work are offered under the GPL v2 or later. Original reverse-engineering notes and this Python/PPD code are also offered under the same terms.

Brother, Brother DCP-T230 are trademarks of Brother Industries, Ltd. This project is not affiliated with or endorsed by Brother Industries.