Guide

Device access (Linux)

The printer appears as the kernel usblp node /dev/usb/lp0. Give your user access by joining the lp group (or install the bundled 99-vkp80iii.rules):

sudo usermod -aG lp "$USER"     # then log out/in, or for this shell:
sg lp -c 'python -m vkp80iii status'

TAG+="uaccess" does not work for this device — systemd-logind does not grant ACLs on the usblp character node, so group ownership is the reliable path.

Connecting & layout

from vkp80iii import Printer

p = Printer(paper_width_mm=80, left_offset_dots=0)   # opens /dev/usb/lp0
p.begin()        # reset (ESC @) + apply left margin and print width

• paper_width_mm — usable print width; capped at the head's 576 dots (72 mm).
• left_offset_dots — horizontal offset from the printer's logical origin to the paper's left edge. It depends on the firmware PRINT WIDTH setup value and the paper guides. Measure it once with the ruler:

python -m vkp80iii calibrate --paper-width-mm 55

Then pass the measured offset (e.g. Printer(paper_width_mm=55, left_offset_dots=12)).

For the common case where the firmware PRINT WIDTH matches the paper, skip the arithmetic and use the for_paper() factory — it derives the print width and the centering offset from the physical roll width and a per-side margin:

p = Printer.for_paper(width_mm=58)              # -> paper_width_mm=55, left_offset_dots=12
p = Printer.for_paper(width_mm=58, margin_mm=2) # wider safety margin (-> offset 16)

Text & formatting

Formatting methods are chainable and return self:

from vkp80iii import Justify, Underline

p.align(Justify.CENTER).bold().double_strike().textln("HEADER")
p.bold(False).double_strike(False)
p.underline(Underline.SINGLE).textln("underlined").underline(0)
p.align(Justify.LEFT).textln("normal text")

Text is encoded with the active code page's codec. begin()/reset() revert the device to PC437 and resync the codec; call p.code_page(CodePage.WPC1252) for Western European accents.

Barcodes

from vkp80iii import Barcode

p.barcode(Barcode.EAN13, "4006381333931")   # 1D, validated length + charset
p.qrcode("https://example.com", module_size=6)
p.pdf417("payload", columns=0)

DataMatrix / Aztec

The ROM 7.11 firmware does not implement DataMatrix or Aztec — the data leaks through as text. Render them host-side as a raster image instead (see examples/render_2d.py) and print with p.image(...).

Images & logos

p.image("logo.png")                 # auto-fits width, tall images are banded

Logos can also be stored in flash and printed by number:

p.upload_logo(200, "logo.png")      # FS 0x94
# IMPORTANT: power-cycle the printer once, then:
p.print_logo(200)

The printer only re-indexes flash logos on boot, so a power-cycle after upload is required before print_logo finds the new logo. Slots 1/2 hold the factory demo logo — use your own number (e.g. 200).

Cutting, presenter & ejector

p.cut()                 # total cut at the current position
p.cut(feed=40)          # feed then total cut
p.present()             # cut + present the ticket at the bezel
p.eject()               # eject a presented ticket to the customer
p.retract()             # pull an un-taken ticket back in

The VKP80III cutter is total cut only — there is no partial cut.

Status & kiosk monitoring

st = p.status()                     # full 6-byte status block
print(st.paper_present, st.cover_open, st.ready)
if not p.is_ready():
    ...                             # paper out / cover open / error

print(p.paper_remaining_cm(), p.cut_count())   # maintenance counters

For kiosk operation you can either poll status() on an interval, or have the printer push status changes automatically:

p.enable_auto_status_back()         # printer emits a frame whenever status changes
while True:
    frame = p.read_auto_status()    # None if nothing pending
    if frame:
        handle(frame)

See examples/monitor.py for a complete poll-and-push monitor.

Transports

Printer() defaults to UsbLpTransport (/dev/usb/lp0). Other backends:

from vkp80iii import Printer, PyUsbTransport, SerialTransport, DummyTransport

Printer(PyUsbTransport())                 # libusb, no kernel usblp driver
Printer(SerialTransport("/dev/ttyUSB0"))  # RS232 models
Printer(DummyTransport(), auto_open=False) # in-memory, for tests / dry runs