WalkPrint

WalkPrint is a Flipper Zero external app for a WalkPrint / YHK-style thermal printer that can print typed messages, .txt files from the SD card, and 384px wide BMP images. It uses a single live path through an external ESP32 bridge instead of pretending the Flipper can talk to a Classic Bluetooth printer on its own.

Features	Features
Print custom typed messages	Print .txt files from the SD card
Print 384px BMP images from the SD card	Discover nearby supported printers
Generate QR BMPs on-device and save/print them	Generate Code 128 barcode BMPs on-device and save/print them
Connect through the ESP32 Classic Bluetooth bridge	Scan Wi-Fi from the bridge
Adjust density, font size, spacing, and font family	Save printer address and print settings

The app talks to an ESP32-WROOM over Flipper USART at 115200 8N1, and the ESP32 handles:

• Classic Bluetooth SPP printer discovery and connection
• raw printer byte transport
• Wi-Fi scan/status helpers

The build scripts prefer your local Momentum firmware checkout when it is present.

Current State

• The Flipper app builds cleanly against Momentum and outputs dist/walkprint.fap.
• The app UI now includes printer discovery, Wi-Fi scan, configurable message font size/family settings, .txt printing from the SD card, and BMP printing from the SD card.
• The live transport in walkprint_transport_live.c uses Flipper header pins 13/14 (PB6/PB7) at 115200.
• The ESP32 bridge sketch lives at esp32_bridge/walkprint_esp32_bridge/walkprint_esp32_bridge.ino.
• The optional WalkPrint Bridge is a PC-side Python script under bridge/ for desktop helpers like image conversion, QR/1D barcode BMP generation, and direct PC printing. It is not required for the Flipper Zero app.

ESP32 Bridge

The ESP32 bridge is the practical transport layer for this setup because it can own Classic Bluetooth SPP while the Flipper app stays on a supported UART link.

Hardware Photos

Files:

• Bridge sketch: esp32_bridge/walkprint_esp32_bridge/walkprint_esp32_bridge.ino
• Bridge notes: esp32_bridge

Wiring:

• ESP32 GPIO17 TX -> Flipper PB7 RX
• ESP32 GPIO16 RX -> Flipper PB6 TX
• GND -> GND

Protocol examples:

• PING
• BT_SCAN
• BT_CONNECT|25:00:35:00:03:57
• BT_WRITE_HEX|...
• WIFI_SCAN

Project Layout

.
|-- .gitignore
|-- README.md
|-- application.fam
|-- app_ui.c
|-- app_ui.h
|-- build.sh
|-- deploy.sh
|-- walkprint_app.c
|-- walkprint_app.h
|-- walkprint_config.h
|-- walkprint_debug.c
|-- walkprint_debug.h
|-- walkprint_protocol.c
|-- walkprint_protocol.h
|-- walkprint_transport.h
`-- walkprint_transport_live.c

What You Can Edit

Printer-specific placeholders live in walkprint_config.h.

Edit these first:

• walkprint_config_init_frame
• walkprint_config_start_print_frame
• walkprint_config_end_print_frame
• walkprint_config_feed_frame
• walkprint_config_raw_frame
• walkprint_demo_receipt_lines

Build

export FLIPPER_FW_PATH=/path/to/Momentum-Firmware
./build.sh

Optional:

./build.sh --fw-path /path/to/Momentum-Firmware
./build.sh --fw-path /path/to/Momentum-Firmware --copy

The Windows build script also works directly with your local checkout:

./build.ps1 -FirmwareDir C:\Users\jasammarco.ENG\Projects\Momentum-Firmware

Deploy

Mounted SD card:

./deploy.sh --mount /Volumes/FLIPPER

qFlipper CLI:

./deploy.sh

App Menu

• Discover Printer
• Connect
• Print Message
• Print TXT
• Print QR
• Print Barcode
• Print BMP
• Feed Paper
• WiFi Scan
• Settings
• About

The app now shows:

• connection state
• the saved printer address, once discovery or manual entry sets it
• the configured density placeholder
• the configured font size from 1-10
• the selected font family
• the latest bridge discovery or Wi-Fi scan result
• BMP print status for .bmp files selected from storage
• generated QR BMP status for Flipper-side save and print
• generated barcode BMP status for Flipper-side save and print
• TXT print status for .txt files selected from storage
• persisted settings after the app closes, including printer MAC, message, BMP path, and print options

The desktop bridge now adds:

• python bridge/walkprint_bridge.py image <path> to send an image directly
• python bridge/walkprint_bridge.py convert-image <path> to generate the printer payload without sending
• python bridge/walkprint_bridge.py make-qr --text "..." to generate a 384px BMP QR code for Flipper-side Print BMP
• python bridge/walkprint_bridge.py make-qr --input-file path.txt to generate a QR code from a file
• python bridge/walkprint_bridge.py make-barcode --text "..." to generate a 384px BMP 1D barcode for Flipper-side Print BMP
• python bridge/walkprint_bridge.py make-barcode --input-file path.txt to generate a 1D barcode from a file
• python bridge/walkprint_bridge.py qr --text "..." to generate and print a QR code directly
• python bridge/walkprint_bridge.py barcode --text "..." to generate and print a 1D barcode directly
• .\bridge\send_image.ps1 to select an image with a Windows file picker and send it
• .\bridge\send_image.ps1 -BmpOnly to pick only .bmp files and send them at the default 384px print width

Notes

• The Flipper talks to the printer through the ESP32 bridge over UART; it does not open the printer's Classic Bluetooth link on its own.
• Print TXT reads a .txt file from the Flipper SD card, keeps line breaks, and prints it across as many text pages as needed. While a multi-page TXT job is running, Back cancels after the current page finishes.
• Print QR now generates a QR BMP directly on the Flipper. The app first collects QR text, then asks for the BMP filename, then offers Save + Print through the existing BMP confirmation flow. The current on-device encoder uses QR version 3-L and accepts up to 53 characters.
• Print Barcode now generates a Code 128 B BMP directly on the Flipper. The app first collects barcode text, then asks for the BMP filename, then offers Save + Print through the same confirmation flow. The current on-device encoder accepts printable ASCII and keeps input to 24 characters so the bars still fit at 384px.
• The built-in text renderer is best for standard printable ASCII. If a text file uses Unicode art, block characters, or other extended symbols, convert it to an image and use Print BMP instead.
• Print BMP expects a .bmp file on the Flipper SD card that is exactly 384px wide. Files with other widths are rejected by the app.
• After selecting a BMP, the Flipper now shows a confirmation screen with OK to print and Back to cancel. Generated QR and barcode jobs reuse the same screen for Save + Print, and the saved file name comes from the filename entered on the Flipper keyboard. The app normalizes spaces to underscores, keeps safe filename characters, and appends .bmp when needed.
• The new QR and 1D barcode helpers in bridge/walkprint_bridge.py generate 384px BMP files specifically so they can be copied to the Flipper SD card and printed with the existing Print BMP menu item.
• Use the Arduino IDE to compile and upload the ESP32 bridge sketch, and make sure the partition option matches the included partitions.csv setup.
• Good next additions for the bridge would be printer status polling, Wi-Fi connect commands, and better paging for larger Bluetooth scan results.