LW Raster Protocol

The classic LabelWriter raster wire protocol, spoken by DYMO's LabelWriter 3xx (including 330 Turbo), 4xx (400, 400 Turbo, 450, 450 Turbo, 450 Twin Turbo, 4XL, SE450, Wireless), and the LabelWriter Duo's label-side engine. The Duo's tape-side engine is a separate D1 tape device.

The 5xx-generation successor uses a different protocol — see LW5 raster.

USB topology

Single full-speed USB 2.0 Printer-class device. VID is 0x0922 (DYMO-CoStar); PIDs are listed on the Hardware page.

Configuration 1
  Interface 0 — Printer class (bInterfaceClass 0x07)
    Bulk OUT  (print data)
    Bulk IN   (1-byte status reply)

The LabelWriter Duo enumerates as a composite device with two printer-class interfaces — the label side speaks this protocol, the tape side speaks D1. No mode-switch is required for any LabelWriter chassis.

Opcode vocabulary

Opcode	Bytes	Description
ESC *	1B 2A	Restore default settings.
ESC @	1B 40	Reset all parameters; set Top-of-Form true.
ESC A	1B 41	Get printer status (1-byte reply).
ESC B	1B 42 n	Set Dot Tab — skip n bytes from the left of each row.
ESC c	1B 63	Set print density Light (75 % strobe duty).
ESC d	1B 64	Set print density Medium (87.5 % strobe duty).
ESC D	1B 44 n	Set bytes-per-line for the rows that follow.
ESC e	1B 65	Set print density Normal (100 % strobe duty).
ESC E	1B 45	Form feed — advance the printed label to the tear-off bar.
ESC f 1 n	1B 66 01 n	Skip n lines (0..255).
ESC g	1B 67	Set print density Dark (112.5 % strobe duty).
ESC G	1B 47	Short form feed — advance between labels in a multi-label job.
ESC h	1B 68	Text Speed mode — 300 × 300 dpi (default).
ESC i	1B 69	Barcode and Graphics mode — 300 × 600 dpi.
ESC L	1B 4C n1 n2	Set label length, big-endian dot count (n1 = MSB, n2 = LSB).
ESC q	1B 71 n	Select roll (Twin Turbo only): '0' auto, '1' left, '2' right.
ESC V	1B 56	Return 10-byte ASCII model + firmware revision string.
ETB	17 + N	Transfer one raster line, run-length encoded.
SYN	16 + N	Transfer one raster line, uncompressed.

n is a single byte unless otherwise noted. All multi-byte counts are stated explicitly in each opcode's section — ESC L is the only two-byte count, and its order is MSB first.

Print job structure

A complete job is a single byte stream sent to the OUT endpoint:

ESC @                  — reset printer
ESC D bytesPerLine     — set raster row width (default 84 for 672-dot heads)
ESC <density>          — print density (c / d / e / g)
ESC <mode>             — text (h) or graphics (i)
ESC L n1 n2            — set label length, big-endian dot count
[ESC q n]              — select roll (Twin Turbo only)
[per copy]
  [for each row]
    SYN row…           — one raster line, uncompressed
    or
    ETB row…           — one raster line, run-length encoded
  ESC E                — form feed
ESC A                  — get printer status (1-byte reply)

ESC E after each copy advances the label past the tear bar; emit ESC G between copies and ESC E only after the last copy to skip the reverse-feed step on every label but the last.

Raster rows may be intermixed: any individual row can be SYN (uncompressed) or ETB (compressed) regardless of what surrounded it. Both decode to exactly the bytes-per-line set by the preceding ESC D.

ESC * — restore default settings

1B 2A

Resets all internal parameters to their defaults. Acted upon when received. The byte stream the LabelWriter encoder ships uses ESC @ at the head of a job instead.

LabelWriter 450 Series Technical Reference, p. 17.

ESC @ — reset printer

1B 40

Resets Dot Tab, bytes-per-line, label length, and other parameters to their defaults, and sets Top-of-Form true. Any data still in the print buffer is discarded. Emitted as the first command of every job.

LabelWriter 450 Series Technical Reference, p. 17.

ESC A — get printer status

1B 41

The printer replies with one byte on the IN endpoint. Bit meanings (1 = condition holds):

Bit	Mask	Meaning
0	0x01	Ready (paper in, no jam). Always returned as 1.
1	0x02	Top of Form.
5	0x20	No paper / labels.
6	0x40	Paper jam.
7	0x80	Printer error (jam, invalid sequence, and so on).

Bits 2, 3, 4 are reserved. A healthy idle printer returns 0x03 (Ready + Top of Form). Bit 7 is also set when an out-of-paper condition is detected.

LabelWriter 450 Series Technical Reference, p. 17.

ESC B — set Dot Tab

1B 42 n

Shifts the starting dot position to the right by n bytes (i.e. 8 × n dots), effectively widening the left margin. Valid range 0..83 on a 672-dot head. If n is increased, the bytes-per-line must be decreased by the same amount; the firmware does not cross-check the two values, so the host must keep them consistent.

LabelWriter 450 Series Technical Reference, p. 15.

ESC c — set print density Light

1B 63

Sets the strobe time to 75 % of the standard duty cycle.

LabelWriter 450 Series Technical Reference, p. 19.

ESC d — set print density Medium

1B 64

Sets the strobe time to 87.5 % of the standard duty cycle.

LabelWriter 450 Series Technical Reference, p. 19.

ESC D — set bytes per line

1B 44 n

n is the number of payload bytes that follow each raster opcode (SYN or ETB), in the range 1..84 for 672-dot heads. The default is 84 (84 × 8 = 672 dots). For the 1248-dot 4XL head the value is 156. The firmware does not validate n against the head width; out-of-range values produce undefined output.

LabelWriter 450 Series Technical Reference, p. 15.

ESC e — set print density Normal

1B 65

Sets the strobe time to 100 % of the standard duty cycle. This is the default.

LabelWriter 450 Series Technical Reference, p. 19.

ESC E — form feed

1B 45

Advances the most recently printed label so it can be torn off at the tear bar. Because this advances past the next label's starting print position, a reverse-feed is automatically performed before the next label prints. In continuous-feed mode (negative ESC L value), this feeds enough dot lines to push the last printed line past the tear bar instead.

LabelWriter 450 Series Technical Reference, p. 16.

ESC f 1 n — skip n lines

1B 66 01 n

Advances the label by n lines (0..255), where a "line" is one dot row at the current resolution (set by ESC h or ESC i). The literal 0x01 byte is part of the opcode, not a parameter. Buffered with the print data so it takes effect inline; emitted once per skip.

LabelWriter 450 Series Technical Reference, pp. 17–18.

ESC g — set print density Dark

1B 67

Sets the strobe time to 112.5 % of the standard duty cycle.

LabelWriter 450 Series Technical Reference, p. 19.

ESC G — short form feed

1B 47

Advances the next label into print position without performing the reverse-feed step that follows ESC E. The previous label remains partially inside the printer and cannot be torn off. Use between labels in a multi-label job; the final label needs ESC E to reach the tear-off position.

LabelWriter 450 Series Technical Reference, p. 16.

ESC h — Text Speed mode

1B 68

Selects 300 × 300 dpi printing — the default, high-speed mode.

LabelWriter 450 Series Technical Reference, p. 18.

ESC i — Barcode and Graphics mode

1B 69

Selects 300 × 600 dpi printing. The printer steps half as far in the feed direction per dot row, producing smaller and more precise dots at the cost of speed. Useful for small barcodes and detail-sensitive graphics.

LabelWriter 450 Series Technical Reference, p. 18.

ESC L — set label length

1B 4C n1 n2

Sets the label length to a 16-bit dot count in 300ths of an inch. n1 is the MSB, n2 is the LSB. Default 3058 (≈10.2 in).

The label length is the maximum distance the printer travels while searching for the next top-of-form mark; print lines and feed lines count toward this distance. It is conventionally set slightly larger than the true label length to ensure the top-of-form mark is found before the search is terminated. The firmware does not compare this value against the loaded label stock — the host is responsible for not overrunning the label area.

Any negative two-byte value (0x8000..0xFFFF) puts the printer in continuous-feed mode, in which ESC E and ESC G feed a fixed number of dot lines from the current position rather than seeking a top-of-form mark.

LabelWriter 450 Series Technical Reference, p. 16.

ESC q — select roll (Twin Turbo)

1B 71 n

Twin Turbo only. n selects the source roll:

Byte	Selection
'0' (0x30)	Automatic — firmware toggles between rolls as they empty.
'1' (0x31)	Left roll.
'2' (0x32)	Right roll.

In Automatic mode the firmware assumes both rolls carry the same media.

LabelWriter 450 Series Technical Reference, pp. 16–17.

ESC V — return revision

1B 56

Returns a 10-byte ASCII string on the IN endpoint:

• Bytes 0–6: 7-digit model number (e.g. 93089).
• Byte 7: lowercase letter (commonly v).
• Bytes 8–9: 2-digit firmware version (e.g. 0N).

Example reply: 98039v0K.

LabelWriter 450 Series Technical Reference, p. 18.

SYN — transfer print data

16 b0 b1 ... b(N-1)

0x16 is the SYN opcode. The N payload bytes carry one raster line of pixel data, where N is the value set by the most recent ESC D. Bit 7 of b0 is the leftmost dot at the start of the print head; bit 0 of b(N-1) is the rightmost. The data is not length-prefixed — the prior ESC D is the only source of truth for row width.

After receiving 0x16, the firmware ingests exactly N bytes as raster pixels, treating any embedded ESC, SYN, or ETB bytes as pixel data — there is no escape mechanism inside a raster row.

LabelWriter 450 Series Technical Reference, p. 18.

ETB — transfer compressed print data

17 c0 c1 ... ck

0x17 is the ETB opcode. The payload is a run-length encoding of one raster line that decodes to exactly 8 × N pixels, where N is the current bytes-per-line. Each compressed byte encodes one run:

Bit	Function	Value
7	Pixel colour	0 = white, 1 = black
6–0	Run length − 1	0..127 (so run length is 1..128)

Examples: 00 = 1 white pixel; 80 = 1 black pixel; 0F = 16 white pixels; FF = 128 black pixels. The sum of pixels per line must equal bytesPerLine × 8; no error checking is done. Compressed and uncompressed rows may be intermixed.

LabelWriter 450 Series Technical Reference, p. 21 (Appendix A).

Synchronisation recovery

Raster bytes are not framed: after SYN or ETB the firmware reads exactly bytesPerLine bytes as pixels, regardless of their values. If the host and firmware get out of sync the device may sit waiting for raster bytes the host is no longer sending. To force the parser back to a command-accepting state the host can send 85 consecutive ESC (0x1B) bytes — one more than the maximum bytes-per-line, so the run is guaranteed to exhaust any in-progress raster expectation and leave the parser looking for a command byte.

LabelWriter 450 Series Technical Reference, p. 9.

References

• LabelWriter® 450 Series Printers Technical Reference Manual, Sanford, L.P. (Rev. 10/09). Authoritative byte-level reference for the 450, 450 Turbo, 450 Twin Turbo, 450 Duo (label side), and 4XL. Cited inline by page; not redistributed.