Technical specifications
- Manufacturer
- Nordic Semiconductor
- MCU / Part
- nRF52840
- Architecture
- Arm Cortex-M4F
- Logic voltage
- 3.0/3.3 V board domain
- Recommended input
- USB or board supply options
- GPIO limits
- Not 5 V tolerant; use configured board voltage
- Flash
- 1 MB
- RAM
- 256 KB
- Clock
- 64 MHz
- ADC
- 12-bit SAADC with oversampling
- DAC
- None
- PWM / timers
- 4 PWM units
- Connectivity / buses
- Bluetooth LE, Thread/Zigbee 802.15.4, NFC, USB, UART, I²C, SPI, I²S
- Programmer
- On-board J-Link / SWD
- Debugger
- On-board J-Link
Pin reference
| Pin | Type | Main functions | Electrical note |
|---|
| P0/P1 GPIO | GPIO/Peripheral | Flexible peripheral mapping | Board voltage only |
| NFC1/NFC2 | NFC/GPIO | NFC antenna or GPIO configuration | Special configuration required |
| SWDIO/SWDCLK | Debug | SWD interface | On-board debugger connected |
| VBUS/USB D+/D− | USB | USB device interface | Follow USB routing |
| VDD/GND | Power | Configurable target supply | Do not apply 5 V to GPIO |
Features and compatibility
BLE, USB, NFC, cryptography, low power
Verify the exact board revision and manufacturer documentation before wiring. Never apply 5 V to a 3.3 V-only GPIO.
Open official datasheet/documentation ↗Deep reference
Architecture, electrical limits and engineering guidance
- Exact MCU / SoC
- nRF52840
- Maximum GPIO current
- Not 5 V tolerant; use configured board voltage
- EEPROM / NVM
- Use internal data flash/NVS/flash emulation where supported; include wear levelling and power-fail protection.
- Interrupts / DMA
- GPIO/peripheral interrupts are available. DMA capability is device-specific; confirm channels, request mapping and memory-access restrictions in the reference manual.
- Sleep and power
- Use the light/deep/standby modes offered by the device. Measure board current because regulators, LEDs and USB interfaces can dominate MCU sleep current.
- Boot and programming
- Confirm boot-mode pins before reset. Use the official bootloader/programmer and retain a recoverable debug/programming header.
Special and restricted pins
Reset, clock, debug, USB, crystal and analogue-reference pins have special electrical or boot functions. Avoid loading them until the boot sequence is understood.
Boot-strapping warnings
Check BOOT/RESET/programming pin truth tables before assigning peripherals; keep required pull resistors fitted.
I/O voltage warnings
3.0/3.3 V board domain domain. Never exceed VDD + permitted injection limits; level-shift incompatible modules and share ground only where safe.
Memory map and registers
Start with the memory map: code flash, SRAM, peripheral registers and system/control space. Use vendor headers instead of hard-coded addresses, then study GPIO direction/output/input, clock-enable, interrupt and timer registers.
Board-selection guidance
Choose this device only after checking logic voltage, required interfaces, memory margin, timers/ADC resolution, debugging access, package availability and long-term tool support.
Common faults and troubleshooting
Not detected: verify data USB cable, driver, boot mode and target power. Upload failure: select the exact target and programmer. Unstable operation: inspect supply ripple, reset, clock and watchdog cause. Wrong readings: check reference voltage, grounding, pin multiplexing and calibration.
Interview and viva questions
What is the difference between an absolute maximum and an operating limit?
Absolute maximum prevents damage; reliable design stays within recommended operating conditions.
Why must peripheral clocks be enabled?
Many MCUs gate clocks to save power; registers may not operate until the peripheral clock is enabled.
Why preserve a debug interface?
It enables programming, breakpoints, fault inspection and production recovery.
What causes GPIO damage?
Over-voltage, excess source/sink current, negative injection, ESD or driving against another output.
