TF38-UDM

A BLE-connected e-paper display badge: a custom nRF52 board that receives a bitmap image over Bluetooth Low Energy and renders it on a 152x152 e-paper panel.

This repo holds the original work only — hardware design, the e-paper driver, the BLE service, and the image-conversion tooling — not the vendored Nordic nRF5 SDK the firmware builds against. See Building the firmware below for how to combine the two.

The e-paper driver (Software/components/drivers_ext/epd/)

This is the core of the project: a from-scratch driver supporting two different e-paper panel command protocols (epd_protocol_a/epd_protocol_b, covering Good Display and DKE/Dalian panel families — GDEW/GDEP/GDEQ and DEPG part numbers), a bit-level SPI transport (epd_spi, epd_spi_port_nrf51822), run-length encoding for the panel's compressed update path (rle), and partial-refresh scan-back handling (scanback) so only changed regions of the display need a full refresh cycle.

Other components

• Hardware (Hardware/): KiCad/Gerber fabrication output (TF38-UDM_Rev.A_231124) — Gerbers, drill files, BOM, pick-and-place CSV, and a STEP model for the board.
• BLE service (Software/components/ble/ble_services/ble_tf38_udm/): a custom GATT service (Nordic UART Service pattern) that receives image data and commands over BLE and hands them off to the display driver.
• Board definition (Software/components/boards/TF38_UDM.h): pin mapping and peripheral config for the custom board, in the shape the nRF5 SDK's board-support layer expects.
• Firmware app (Software/examples/ble_peripheral/ble_app_epd/): the application that ties it together — derived from Nordic's ble_app_uart example, extended to validate a DZ38 image header (signature, width, height, data size) over BLE and drive the display. Includes prebuilt project files for the TF38_UDM board (GCC/Makefile, Keil, IAR, SEGGER Embedded Studio) across s113/s140 SoftDevice variants.
• Image tools (Online/): Python scripts (ImgToDZ38.py, DZ38toPNG.py, ImgToXZ38.py, XZ38toPNG.py, dithering_converter.py) that convert images to/from the device's packed 1-bit DZ38/XZ38 formats using Floyd-Steinberg dithering, plus a UDP server.py/client.py pair for fragmenting and transferring files to a conversion service.

Building the firmware

The firmware is an nRF5 SDK example project and needs the SDK itself, which isn't vendored in this repo:

1. Download nRF5 SDK v17.1.0 from Nordic Semiconductor.
2. Copy this repo's Software/components/ and Software/examples/ contents into the matching paths under the SDK root (i.e. <SDK_ROOT>/components/..., <SDK_ROOT>/examples/...).
3. Build the TF38_UDM board target (not the pca10040/pca10056/pca10100 Nordic dev-kit targets, which are Nordic's own and not included here) under examples/ble_peripheral/ble_app_epd/TF38_UDM/<s113|s140>/, with GCC (armgcc/Makefile), Keil (arm5_no_packs/*.uvprojx), IAR, or SEGGER Embedded Studio.

Tech stack

• Nordic nRF52 SoftDevice BLE stack (nRF5 SDK v17.1.0)
• C firmware, multiple toolchains (GCC/ARM, Keil MDK, IAR, SES)
• Python 3 (Pillow) for image tooling
• KiCad-generated Gerbers for PCB fabrication

License

MIT — see LICENSE. Software/examples/ble_peripheral/ble_app_epd/main.c additionally carries Nordic Semiconductor's own copyright/license terms for the unmodified portions of that file (see the file header and LICENSE for details).