BLE HID Keyboard Example

This is a Zephyr / nRF Connect SDK example for a BLE HID keyboard-style device.

Features

• BLE HID over GATT keyboard report map
• Bonding, settings persistence, and BLE privacy
• Battery service integration
• Connection callbacks and advertising restart
• Explicit press/release HID reports
• Debounced GPIO input scanner using sw0-sw3 devicetree aliases
• Long-press factory reset path for clearing BLE bonds
• Hardware watchdog setup and feed policy
• Power management hooks
• MCUmgr/SMP over BLE OTA/DFU configuration
• Qualification checklist for host interoperability and reliability testing

Layout

ble-hid-firmware-example/
  CMakeLists.txt
  prj.conf
  README.md
  boards/
    nrf52840dk_nrf52840.overlay
  src/
    main.c
    ble_hid.c
    ble_hid.h
    battery.c
    battery.h
    input_scanner.c
    input_scanner.h
    factory_reset.c
    factory_reset.h
    power.c
    power.h
    app_watchdog.c
    app_watchdog.h
  tests/
    qualification_checklist.md

Build

From an initialized Zephyr or nRF Connect SDK environment:

west build -b nrf52840dk_nrf52840 .
west flash

Adjust the board name for your target.

Hardware Assumptions

The input scanner uses Zephyr devicetree aliases:

• sw0: sends keyboard A, also acts as factory-reset button at boot
• sw1: sends keyboard B
• sw2: sends keyboard C
• sw3: sends keyboard D

Boards without those aliases still build; missing buttons are skipped. For a keyboard matrix, replace input_scanner.c with row/column scanning while keeping the same input_scanner_event_handler_t boundary.

Factory Reset

Hold sw0 during boot for 8 seconds. The firmware clears all BLE bonds for the default identity and reboots. In a shipping product, combine this with an LED or haptic acknowledgement so users know the reset was accepted.

OTA/DFU

This template enables MCUboot and MCUmgr image upload over BLE. A production product also needs:

• Signed images and key management
• Partition layout reviewed for the exact flash size
• Upgrade, rollback, and interrupted-transfer testing
• A host-side release process using mcumgr or your mobile app

Example host flow after building a signed image:

mcumgr --conntype ble --connstring peer_name="ProdBLE Keyboard" image upload build/zephyr/app_update.bin
mcumgr --conntype ble --connstring peer_name="ProdBLE Keyboard" image list
mcumgr --conntype ble --connstring peer_name="ProdBLE Keyboard" image confirm
mcumgr --conntype ble --connstring peer_name="ProdBLE Keyboard" reset

Production Notes

Before shipping, replace placeholder battery measurement with calibrated ADC logic, review power states against your board schematic, tune connection parameters against latency/current targets, and run the qualification checklist in tests/qualification_checklist.md.