Nordic nRF Firmware Dev Guide

Tips

• nRF52832/52840: Best for BLE applications, mesh networking, and low-power sensors
• nRF5340: Dual-core for complex applications requiring both connectivity and processing
• nRF54 Series: Latest generation with improved power efficiency and performance
• nRF7002: WiFi 6 companion IC for cloud-connected applications
• nRF9160: Cellular IoT (LTE-M/NB-IoT) with GPS for asset tracking and remote monitoring

Resources

Tips

• BLE: Short-range, low-power, ideal for wearables and sensors
• Thread/Zigbee: Mesh networking for smart home and industrial IoT
• WiFi: High bandwidth for streaming and cloud connectivity
• LTE-M/NB-IoT: Wide-area coverage for remote assets
• Consider multi-protocol support (BLE + Thread) for future flexibility

Reference

System Architecture Layers:
- Application Layer: Business Logic, State Machines, Protocol Handlers
- Middleware Layer: nRF Connect SDK Libraries, Zephyr Subsystems
- OS Layer: Zephyr RTOS (threads, timers, workqueues)
- HAL Layer: Nordic HAL / Zephyr Device Drivers
- Hardware Layer: Nordic SoC + External Peripherals

Tips

• Separate hardware-specific code into HAL modules
• Use Zephyr's native drivers when available
• Plan memory layout for SoftDevice + application + OTA

Reference

Power Budget Calculation Example:
Active Mode (BLE advertising @ 1s interval):
  Radio TX: 4.6mA x 1ms = 4.6uAs per interval
  CPU: 3mA x 0.5ms = 1.5uAs per interval
  Average: ~6uA continuous

Sleep Mode (System ON, RTC running): 1.5uA base

Target: CR2032 (225mAh) for 2 years
  Available: 225mAh / (2 years x 8760 hours) = 12.8uA
  Budget: 10uA average leaves headroom

Tips

• Use Nordic Power Profiler Kit II for accurate measurements
• Account for peak currents when sizing batteries
• Include all peripherals in power calculations
• Plan for temperature variations affecting battery capacity

Resources

Tips

• Check pin multiplexing constraints in the datasheet
• Reserve pins for programming/debugging (SWD)
• Consider peripheral power domains for low-power modes
• Plan for hardware flow control on UART if needed

Tips

• nRF52: Software-based security, CryptoCell for crypto acceleration
• nRF53/54: Arm TrustZone for hardware isolation
• nRF9160: Trusted Firmware-M (TF-M) for secure processing
• Plan key provisioning and storage strategy early

Reference

Key apps to install via nRF Connect for Desktop:
- Toolchain Manager: Install and manage SDK versions
- Programmer: Flash firmware to devices
- Bluetooth Low Energy: Debug BLE connections
- Power Profiler: Analyze power consumption
- Serial Terminal: UART communication

Tips

• Keep nRF Connect for Desktop updated for latest tool versions
• Install all recommended apps for comprehensive development support
• Toolchain Manager handles SDK and toolchain version management

Resources

Reference

SDK structure after installation:
~/ncs/
├── nrf/           # Nordic-specific code and samples
├── zephyr/        # Zephyr RTOS core
├── modules/       # Third-party modules (mbedTLS, etc.)
├── bootloader/    # MCUboot bootloader
└── tools/         # Build tools

Verify installation:
$ west --version
$ cmake --version

Tips

• Use LTS (Long Term Support) SDK versions for production projects
• nRF Connect SDK v2.x uses west for build management
• Keep a backup of working SDK versions before upgrading

Resources

Tips

• Install the full nRF Connect Extension Pack (includes C/C++, CMake, DTS)
• Use the nRF Connect sidebar for build, flash, and debug operations
• Configure IntelliSense for accurate code completion

Resources

Reference

Key commands:
$ nrfutil version             # Check installation
$ nrfutil device list         # List connected devices
$ nrfutil device program --firmware app.hex  # Flash firmware
$ nrfutil device reset        # Reset device
$ nrfutil device recover      # Recover locked device

West build commands (Zephyr):
$ west build -b nrf52840dk_nrf52840  # Build for target
$ west flash                          # Flash to device
$ west debug                          # Start debug session

Tips

• Add nrfutil to your PATH for easy access
• Use --snr flag to target specific device when multiple connected
• Combine with west for streamlined workflow

Resources

Tips

• Update DK firmware using nRF Connect Programmer
• Check jumper settings for power source selection
• Install USB drivers if not automatically detected
• Use board's onboard J-Link for debugging (no external debugger needed)

Reference

Recommended .gitignore for nRF Connect SDK projects:
build/
*.pyc
__pycache__/
.west/
*.log
*.elf
*.hex
*.bin
.vscode/settings.json
*.DS_Store

Tips

• Track prj.conf, overlay files, and Kconfig in version control
• Don't commit build directories or SDK files
• Use Git tags to mark firmware releases
• Include hardware revision in commit history

Reference

Example overlay file (nrf52840dk.overlay):
Enable I2C with BME280 sensor at address 0x76
Configure GPIO for status LED on pin P0.13
Use aliases for hardware-independent code access

Tips

• Use overlays instead of modifying board DTS files
• Check compatible strings in Zephyr bindings documentation
• Use aliases for hardware-independent code
• Validate overlays with 'west build' before flashing

Resources

Reference

Clock configuration in prj.conf:
CONFIG_CLOCK_CONTROL=y
CONFIG_CLOCK_CONTROL_NRF=y

Notes:
- HFCLK (64MHz) is needed for radio and high-speed peripherals
- LFCLK (32.768kHz) runs always for RTC and timers
- Clocks are managed automatically by Zephyr in most cases

Tips

• HFCLK (64MHz) is needed for radio and high-speed peripherals
• LFCLK (32.768kHz) runs always for RTC and timers
• Use external 32kHz crystal for best BLE timing accuracy
• Clocks are managed automatically by Zephyr in most cases

Reference

GPIO setup pattern:
1. Get GPIO device from Device Tree using GPIO_DT_SPEC_GET
2. Check gpio_is_ready_dt() before using GPIO
3. Configure with gpio_pin_configure_dt()
4. For buttons: add interrupt with gpio_pin_interrupt_configure_dt()
5. Use gpio_init_callback() and gpio_add_callback() for ISR

Tips

• Always check gpio_is_ready_dt() before using GPIO
• Use GPIO_DT_SPEC_GET for compile-time device tree access
• Configure interrupt polarity based on hardware (pull-up/pull-down)
• Debounce button inputs in software or hardware

Reference

Enable peripherals in prj.conf:
CONFIG_UART_ASYNC_API=y
CONFIG_I2C=y
CONFIG_SPI=y

Pattern for I2C:
1. Get device with DEVICE_DT_GET(DT_NODELABEL(i2c0))
2. Check device_is_ready() before use
3. Use i2c_write_read() for register access

Tips

• Use async APIs for non-blocking operations
• Check max clock frequencies in peripheral datasheets
• Configure DMA for high-throughput transfers
• Handle bus errors and implement retry logic

Reference

ISR best practice pattern:
1. Keep ISR short - just submit work with k_work_submit()
2. Use k_work_init() to initialize work item in main()
3. Do heavy processing in work handler, not ISR
4. Use volatile for data shared between ISR and main

Tips

• Keep ISRs as short as possible
• Use work queues to defer processing
• Avoid blocking calls (malloc, printf) in ISRs
• Use atomic operations for shared data

Reference

Power management in prj.conf:
CONFIG_PM=y
CONFIG_PM_DEVICE=y
CONFIG_PM_DEVICE_RUNTIME=y

Use pm_device_action_run() to suspend/resume peripherals
Use pm_policy_state_lock_get/put() during critical operations

Tips

• Zephyr automatically enters low-power modes when idle
• Use PM_DEVICE to control individual peripheral power
• Lock power states during time-critical operations
• Profile power with and without PM enabled

Resources

Reference

BLE configuration in prj.conf:
CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y
CONFIG_BT_DEVICE_NAME="MyDevice"
CONFIG_BT_DEVICE_APPEARANCE=833
CONFIG_BT_MAX_CONN=1
CONFIG_BT_MAX_PAIRED=2

Initialization flow:
1. bt_enable(NULL) to initialize stack
2. Define advertising data with BT_DATA macros
3. Register connection callbacks with BT_CONN_CB_DEFINE
4. Start advertising with bt_le_adv_start()

Tips

• Use BT_CONN_CB_DEFINE for static callback registration
• Configure connection parameters for your power/latency needs
• Enable CONFIG_BT_SETTINGS to persist bonding information
• Use nRF Connect mobile app for testing and debugging

Resources

Reference

GATT service pattern:
1. Define custom 128-bit UUIDs with BT_UUID_DECLARE_128
2. Create read/write handlers for characteristics
3. Use BT_GATT_SERVICE_DEFINE to declare service
4. Include BT_GATT_CCC for notification support
5. Use bt_gatt_notify() to send notifications

Tips

• Use 128-bit UUIDs for custom services
• Include CCC (Client Characteristic Configuration) for notifications
• Test with nRF Connect mobile app's GATT viewer
• Consider using Nordic's GATT Service samples as templates

Reference

Thread configuration in prj.conf:
CONFIG_NETWORKING=y
CONFIG_NET_L2_OPENTHREAD=y
CONFIG_OPENTHREAD_NORDIC_LIBRARY_MTD=y
CONFIG_OPENTHREAD_CHANNEL=11
CONFIG_OPENTHREAD_PANID=4660

Use OpenThread API via openthread_get_default_context()

Tips

• Thread requires IEEE 802.15.4 radio (nRF52840, nRF5340)
• Use OpenThread CLI sample for initial testing
• Configure network credentials via CLI or programmatically
• Consider Matter for cross-ecosystem compatibility

Resources

Reference

WiFi configuration in prj.conf:
CONFIG_WIFI=y
CONFIG_WIFI_NRF700X=y
CONFIG_WPA_SUPP=y
CONFIG_NET_L2_WIFI_MGMT=y
CONFIG_NET_DHCPV4=y

Use net_mgmt(NET_REQUEST_WIFI_CONNECT, ...) to connect

Tips

• nRF7002 requires nRF5340 or nRF52840 as host
• Enable WPA3 for enhanced security
• Use low-power modes (TWT) for battery-powered devices
• Test with different access points for compatibility

Resources

Reference

LTE configuration in prj.conf:
CONFIG_LTE_LINK_CONTROL=y
CONFIG_NRF_MODEM_LIB=y
CONFIG_MODEM_INFO=y

Initialization:
1. nrf_modem_lib_init() to start modem
2. lte_lc_register_handler() for events
3. lte_lc_connect_async() to connect to network

Tips

• Use LTE-M for mobility, NB-IoT for stationary sensors
• Configure PSM (Power Saving Mode) and eDRX for power optimization
• Test with nRF Cloud for easy connectivity verification
• Handle network registration and connection loss gracefully

Resources

Reference

State machine pattern:
1. Define states as enum (INIT, IDLE, ADVERTISING, CONNECTED, etc.)
2. Create state handler functions for each state
3. Use function pointer array for state dispatch
4. Implement transition_to() function for state changes
5. Consider Zephyr's SMF for complex state machines

Tips

• Use state machines for complex control flow
• Document state transitions with diagrams
• Handle all edge cases and error states
• Use Zephyr's SMF (State Machine Framework) for complex state machines

Tips

• Scan for your device's advertising packets
• Connect and explore GATT services and characteristics
• Read, write, and enable notifications on characteristics
• View connection parameters and signal strength
• Log data for later analysis

Resources

Reference

Production configuration for accurate profiling:
CONFIG_LOG=n           # Disable logging
CONFIG_ASSERT=n        # Disable asserts
CONFIG_DEBUG=n         # Disable debug

Test all modes: advertising, connected, data transfer, sleep
Calculate: Battery Life = Capacity (mAh) / Average Current (mA)

Tips

• Measure each operating mode separately
• Account for peak currents (radio TX)
• Test at expected temperature range
• Compare measurements against datasheet values
• Use PPK2 trigger mode for event-based capture

Resources

Reference

RF testing checklist:
1. Range testing at various distances
2. Test through walls and obstacles
3. Measure RSSI and packet loss
4. Test with WiFi and other 2.4GHz interference
5. Verify antenna matching and radiation pattern

Tips

• Use nRF Sniffer to capture and analyze packets
• Test with multiple phone models for BLE
• Document RF test results for certification
• Consider antenna placement in enclosure design

Resources

Tips

• Run Bluetooth SIG qualification tests
• Test with official certification equipment if available
• Document compliance for regulatory submissions
• Use Nordic's pre-certified modules to simplify certification

Reference

Integration test checklist:
Hardware: All sensors, actuators, power supply, reset sequence
Software: All tasks, inter-task communication, error handling
System: End-to-end data flow, mobile app, cloud connectivity, OTA

Tips

• Create automated test scripts where possible
• Test failure scenarios (power loss, disconnect)
• Verify behavior across temperature range
• Document test procedures for repeatability

Tips

• Run for days or weeks in realistic conditions
• Monitor memory usage over time
• Log errors and unexpected behaviors
• Test rapid connect/disconnect cycles
• Stress test with maximum data rates

Reference

DFU over BLE configuration in prj.conf:
CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_MCUBOOT_SIGNATURE_KEY_FILE="path/to/key.pem"
CONFIG_NCS_SAMPLE_MCUMGR_BT_OTA_DFU=y
CONFIG_MCUMGR=y
CONFIG_MCUMGR_GRP_IMG=y
CONFIG_MCUMGR_GRP_OS=y

Tips

• Use MCUmgr protocol for standardized update flow
• Test updates with nRF Connect mobile app
• Plan partition sizes for largest expected image
• Implement update progress indication in UI

Resources

Reference

MCUboot configuration in prj.conf:
CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_MCUBOOT_SIGNATURE_KEY_FILE="priv-key.pem"
CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256=y
CONFIG_MCUBOOT_IMAGE_VERSION="1.0.0"

Build signed image:
$ west build -b nrf52840dk_nrf52840
Output: build/zephyr/app_signed.hex

Tips

• Store signing keys securely (HSM for production)
• Use different keys for development and production
• Enable encryption for sensitive firmware
• Test rollback protection mechanism

Resources

Tips

• Use nRF Cloud for quick prototyping
• Implement version checking before download
• Support delta updates to reduce bandwidth
• Track update success/failure rates
• Plan for fleet segmentation (staged rollouts)

Resources

Reference

TrustZone configuration for nRF5340/nRF9160:
CONFIG_ARM_TRUSTZONE_M=y
CONFIG_SPM=y  # Secure Partition Manager

Access protection:
- APPROTECT: Blocks debugger access
- SECUREAPPROTECT: Blocks secure domain access
- Use KMU (Key Management Unit) for secure key storage

Tips

• Enable APPROTECT in production to prevent debugging
• Use TF-M for advanced secure processing (nRF91)
• Implement secure provisioning for keys
• Test that protection cannot be bypassed

Reference

Production prj.conf settings:
CONFIG_LOG=n
CONFIG_ASSERT=n
CONFIG_DEBUG=n
CONFIG_PRINTK=n
CONFIG_SIZE_OPTIMIZATIONS=y
CONFIG_STACK_CANARIES=y
CONFIG_HW_STACK_PROTECTION=y

Build: west build -b board -- -DCONF_FILE=prj_release.conf

Tips

• Create separate debug and release configurations
• Remove all debug output for production
• Enable hardware stack protection
• Verify final image size fits in flash
• Store build artifacts with version tags

Tips

• Use nRF Cloud for device monitoring
• Implement error logging with persistence
• Add heartbeat/health check functionality
• Plan for remote diagnostics capability
• Track key metrics (battery, connectivity, errors)

Resources