Electronut Labs Papyr


Zephyr applications use the nrf52840_papyr board configuration to run on Electronut Labs Papyr hardware. It provides support for the Nordic Semiconductor nRF52840 ARM Cortex-M4F CPU and the following devices:

  • ADC
  • GPIO
  • I2C
  • MPU
  • NVIC
  • PWM
  • RADIO (Bluetooth Low Energy and 802.15.4)
  • RTC
  • SPI
  • UART
  • USB
  • WDT
Electronut Labs Papyr

Electronut Labs Papyr (Credit: Electronut Labs)

More information about the board is available at https://docs.electronut.in/papyr/.


Papyr has two external oscillators. The frequency of the slow clock is 32.768 kHz. The frequency of the main clock is 32 MHz.

Supported Features

The nrf52840_papyr board configuration supports the following hardware features currently:

Interface Controller Driver/Component
ADC on-chip adc
CLOCK on-chip clock_control
FLASH on-chip flash
GPIO on-chip gpio
I2C(M) on-chip i2c
MPU on-chip arch/arm
NVIC on-chip arch/arm
PWM on-chip pwm
RADIO on-chip Bluetooth, ieee802154
RTC on-chip system clock
SPI(M/S) on-chip spi
UART on-chip serial
USB on-chip usb
WDT on-chip watchdog

Connections and IOs


  • LED1 (green) = P0.13
  • LED2 (blue) = P0.15
  • LED3 (red) = P0.14

Push buttons

  • Reset = SW0 = P0.18 (can be used as GPIO also)


  • TX = P0.8
  • RX = P0.7


I2C pins connected to onboard sensors (I2C_0):

  • SDA = P0.5
  • SCL = P0.6


The e-paper display is connected to the chip via SPI on the following pins (SPI_1):

  • SCK = P0.31
  • MOSI = P0.29
  • MISO = P1.1 (not used by the display)

NOTE: P1.1 is pin 33 in absolute enumeration.

Other pins used by the e-paper display are:

  • E-ink enable = P0.11 (cuts off power to the display with MOSFET)
  • CS = P0.30
  • BUSY = P0.3
  • D/C = P0.28
  • RES = P0.2

Programming and Debugging

Applications for the nrf52840_papyr board configuration can be built and flashed in the usual way (see Build an Application and Run an Application for more details); Black Magic Probe debugger presents itself as two USB-serial ports. On Linux, they may come up as /dev/ttyACM0 and /dev/ttyACM1. The first one of these (/dev/ttyACM0 here) is the debugger port. GDB can directly connect to this port without requiring a GDB server by specifying target external /dev/ttyACM0. The second port acts as a serial port, connected to the SoC.


By default, papyr is configured to be used with a blackmagicprobe compatible debugger (see _Bumpy).

Applications are flashed and run as usual (see Build an Application and Run an Application for more details).

Here is an example for the Hello World application.

First, run your favorite terminal program to listen for output.

$ minicom -D <tty_device> -b 115200

Replace <tty_device> with the serial port of Black Magic Probe. For example, under Linux, /dev/ttyACM1.

Then build and flash the application in the usual way.

# On Linux/macOS
cd $ZEPHYR_BASE/samples/hello_world
mkdir build && cd build

# On Windows
cd %ZEPHYR_BASE%\samples\hello_world
mkdir build & cd build

# Use cmake to configure a Ninja-based build system:
cmake -GNinja -DBOARD=nrf52840_papyr ..

# Now run ninja on the generated build system:
ninja flash


Debug and attach configurations are available using Black Magic Probe, and ninja debug, or ninja attach (or with make) are available.

NOTE: You may need to press the reset button once after using ninja flash to start executing the code. (not required with debug or attach)