Drive the thermal pocket printers sold by Lidl under the Tronic, SILVERCREST and Parkside brands over Bluetooth Low Energy — without the official app, and without any cloud service.
The protocol was established by reverse engineering: BLE traffic analysis on
real hardware, then decompilation of the official com.printer.lidloffice
Android application, which embeds the LuckPrinter SDK.
| TRONIC | SILVERCREST |
|---|---|
 |
 |
Both brands ship the same hardware, the same firmware and the same official application: only the logo on the lid differs.
dimer47.github.io/PocketPrinter5890
Open that page in Chrome, Edge or Opera, click Connect, and print. Nothing to install. Web Bluetooth is not available in Firefox or Safari.
| Directory | Contents |
|---|---|
docs/ |
Protocol specification — the reference, independent of any language |
swift/ |
Swift library for macOS, iOS and iPadOS, plus two demo apps |
android/ |
Kotlin library for Android, plus a Compose demo app |
web/ |
TypeScript library for the browser and Capacitor |
The protocol specification is the source of truth. All three implementations follow it; if they ever disagree, the specification is what a fourth one should be written against.
Reimplementing in another language? Read
docs/PROTOCOL_SPEC.md. It is written to be
sufficient on its own: byte sequences, the flow-control algorithm, a
symptom-to-cause table and a minimal pseudocode implementation. No Swift, Kotlin
or TypeScript knowledge needed.
Building an Apple app? See swift/README.md.
Building an Android app? See android/README.md.
Building for the web or with Capacitor? See web/README.md.
TRONIC
IAN 508705_2507
Article Name : Mini Pocket Printer
Model : 5890
Battery : 18500 Lithium Battery 3.7V 1200mAh 4.44Wh
Input : USB-C; 5V = 1A
Manufactured : 09-2025
Reported by the device over BLE: model A2Y, firmware V1.06LY, advertised
as Mini Pocket Printer_BLE.
Print width is 384 dots (48 bytes per line) at 203 dpi, on roughly 56 mm continuous paper.
This is not a DP-L13. The widely available documentation for the L13 describes a 14 mm label printer with a 96-dot raster — a different machine. Applying its specifications here prevents printing entirely.
Each of these cost significant time to find. They are the reason this repository exists rather than a shorter gist.
1. An activation sequence is mandatory. Without 10 FF F1 03 followed by
twelve zero bytes as a separate write, the printer acknowledges every
command and executes nothing — not even a paper feed.
2. 01 nn frames are flow-control credits, not status. The printer
announces how many packets it can accept. Pacing with a fixed delay instead
divides throughput by roughly twenty. Reading one as a reply makes 01 01
look like "battery: 1%".
3. The raster must be sent in bands. A single large GS v 0 command is
dropped. Split into bands of about 24 lines.
Established by printing on paper, not inferred:
| Command | Behaviour |
|---|---|
ESC t — code page |
Ignored. Nine pages tested, nine identical unreadable lines. |
| Non-ASCII characters | Solid block. Transliterate to ASCII. |
GS B — reverse video |
No effect. |
GS ( k — QR code |
Prints as literal text: k1A2k1Ck1E1k1P0... |
GS k — barcode |
Prints as literal text: <I{BMETEO2026 |
Codes therefore have to be rasterised. The vendor app does the same: its SDK exposes no text or code printing at all, only bitmaps.
| Swift | Kotlin | TypeScript | |
|---|---|---|---|
| Protocol, raster, ESC/POS | ✅ | ✅ | ✅ |
| Barcodes (Code 128/39, EAN-13/8) | ✅ | ✅ | ✅ |
| QR codes | ✅ CoreImage | ✅ ZXing | ✅ via qrcode-generator |
| Receipt rendering | ✅ CoreGraphics | ✅ android.graphics | ✅ Canvas |
| Native text receipt | ✅ | ✅ | ✅ |
| Demo app feature parity | ✅ macOS, iOS | ✅ Android | ✅ browser |
| Printing verified on hardware | ✅ macOS + iPhone | ✅ Pixel 7a | ✅ Chrome |
Roughly twenty commands were transcribed from the vendor SDK but never executed on this firmware; they are flagged as such in all three implementations and in the specification.
Firmware update was deliberately left unimplemented: an untested port failing mid-write would leave the printer unusable.
This documents a single unit — A2Y / V1.06LY. Other brand variants or
firmware revisions may behave differently. Useful reports, in order of
interest:
- An untested command actually run on hardware — state model, firmware, command and outcome.
- A different model answering something else to
10 FF 20 F0. - The compressed raster format: the SDK calls
setCompress(true)for the A2Y, implying an encoding not documented here. - USB-C behaviour — does the printer stay awake while powered?
Corrections to any claim in the specification are welcome. Several early diagnoses in this project turned out to be wrong, and are recorded as such.
Built with an AI assistant, and verified on paper.
The assistant read decompiled Java quickly and wrote most of the code. It was also confidently wrong several times — it called the raster width "the main cause" when it was one of two, read flow-control frames as status codes for hours, and wrote a QR encoder producing codes that looked perfect and scanned as nothing.
Every one of those was caught by printing and looking at the paper. Claims in this repository about what the printer does come from an actual print, not from reading code. The ones that do not are marked as untested.
MIT.
Reverse engineering for interoperability, on legally acquired hardware. No vendor code is redistributed: only protocol byte sequences — facts about a wire format — have been documented and reimplemented.