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| name | datamax-dpl-labels |
| description | Print labels on a Datamax printer via DPL. |
| version | 1.0.0 |
| license | MIT |
| platforms | ["linux","macos","windows"] |
| metadata | {"hermes":{"tags":["Printing","Labels","Datamax","DPL","M-4208","Barcode","CSV"]}} |
Use whenever the user wants something printed on a Datamax label printer — shipping labels, asset tags, barcode labels, product labels. Triggers: "print a shipping label", "make barcode labels", "label these boxes", or handing over a CSV of items.
Also use it to diagnose a Datamax: nothing printing, garbled output, scrambled fields, or status queries that hang.
Not for Brother QL, Zebra ZPL, or Dymo printers — different languages.
pip install git+https://github.com/kimasplund/nokka
export NOKKA_DEVICE=/dev/usb/lp0 # or NOKKA_HOST for a networked unit
On Linux, join the lp group once so no sudo is needed:
sudo usermod -aG lp $USER # then log out and back in
# or, without re-login: sg lp -c "nokka ..."
nokka status # printer state
nokka config-label # print its settings ON A LABEL (always works)
nokka test # self-test: fonts, box, 2 barcodes
nokka fonts # 9 internal fonts
nokka barcodes # 23 symbologies
nokka models # resolutions and print widths
# quick one-off
nokka text "BOX 1" "Warehouse A" --barcode ASSET-0042
# batch from CSV
nokka template-init --out label.json
nokka print --template label.json --data rows.csv \
--preview preview.png --dry-run # ALWAYS preview first
nokka print --template label.json --data rows.csv --yes
--dry-run builds the job without sending. --dump shows the raw DPL bytes.
Running from a clone instead of an install: python3 -m nokka.cli ....
DPL's origin is the LOWER-LEFT corner and row counts UPWARD, in hundredths of an inch. On 4x6" media:
So a title near the top is row=520; a barcode lower down is row=200.
{
"label": { "width_in": 4.0, "height_in": 6.0, "heat": 15, "speed": "G" },
"fields": [
{ "type": "text", "data": "{name}", "row": 520, "column": 60, "font": "4" },
{ "type": "barcode", "data": "{sku}", "row": 200, "column": 60,
"symbology": "E", "height": 50 }
]
}
Field types: text, smooth (scalable, in points), barcode, line,
box, image. {column} placeholders pull from the data; matching is case-
and underscore-insensitive. Data may be CSV, TSV, JSON or JSONL.
| Font | Height | Use |
|---|---|---|
| 0-2 | 7-18 dots | small print, addresses |
| 3-4 | 27-36 dots | headings |
| 5-6 | 52-64 dots | large titles |
| 7-8 | OCR-A / OCR-B | machine reading |
| 9 | scalable | any point size via smooth |
Common symbologies: E Code 128, A Code 39, F EAN-13, B UPC-A,
D Interleaved 2 of 5, I Codabar, O Code 93, z PDF-417.
Uppercase id prints human-readable text below the bars; lowercase prints bars only.
Each of these costs an afternoon if met cold.
The eee height field is THREE characters, not four. 040 = 0.40 in.
A fourth digit silently shifts every following field and the label comes
out scrambled. This is the single most likely cause of garbled output.
The model number is not the resolution. The "08" in M-4208 is print
speed (8 ips). Every 4-inch M-Class model is 203 DPI. Confirm with
<STX>KC, which reports the printer key (e.g. 4208-MD10).
Never print through CUPS. A queue bound to a Gutenprint driver rasterises the job and mangles raw DPL — and the driver is often for a different model entirely. Write to the device node directly.
USB status reads work on a DIRECT cable, not over USB/IP. Forwarded
over USB/IP (vhci_hcd) the printer answers one <STX>KC and then stays
silent forever, surviving USB resets and rebinds. Plugged straight in,
<SOH>A and <STX>KC work every time. USB/IP passes bulk-OUT writes but
mangles bulk-IN replies. Keep the printer on a direct cable.
<SOH>D disables immediate commands. Do not send it as a "reset".
Recovery is three valid <SOH> commands one second apart
(Printer.restore_immediate_commands()).
On these older boards the boot loader accepts firmware only through a real IEEE-1284 parallel interface. Every other path fails silently — all bytes accepted, no error, old firmware keeps running:
SEND SOFTWARE): the boot loader does not implement USB — the kernel
logs device not accepting address, error -71 and nothing enumerates.usblp), not a parport, so data still
arrives through the USB print pipeline the boot loader ignores. Verified
on hardware in both READY and download mode.What works: an on-board LPT or a PCI/PCIe parallel card (parport_pc,
giving /dev/lp0), then in READY mode cat firmware.zg > /dev/lp0 — the
equivalent of Honeywell's copy firmware.zg lpt1. Serial is untested.
A failed download is harmless: the original firmware stays operational.
tools/flash_firmware.py refuses USB/IP and requires --download-mode.
Full write-up in docs/firmware-update.md.
nokka print --template label.json --data rows.csv --preview out.png --dry-run
Renders the same records at the same coordinates with real barcode patterns. An approximation, not an emulation — but it catches overlaps, clipping and bad coordinates for free. Look at the PNG before sending to the printer.
| Symptom | Cause |
|---|---|
| Garbled / shifted fields | a 4-digit value in the 3-char eee field |
| Nothing prints | printing through CUPS instead of the device node |
| Permission denied | not in lp group; wrap with sg lp -c "..." |
status returns nothing | printer is on USB/IP; use a direct cable, or config-label |
Printer ignores <SOH> | <SOH>D was sent; send <SOH>A 3x, 1s apart |
| Content off the label | remember row 0 is the BOTTOM edge |
| No device node at all | printer may be in download mode (SEND SOFTWARE) — power cycle it normally |
python3 -m pytest tests/ -q
54 tests, green on Python 3.11-3.14. Four compare output byte-for-byte with worked examples printed in Datamax's own manual.