Blinky, your “Hello World!”, on RedBear Nano 2

This tutorial shows you how to create, build and run the Blinky application on a RedBear Nano 2 board.


  • Meet the prerequisites listed in Project Blinky.

  • Have a RedBear Nano 2 board.

  • Install a patched version of OpenOCD 0.10.0 described in Install OpenOCD.

Create a Project

Create a new project if you do not have an existing one. You can skip this step and proceed to Create the Targets if you already have a project created.

Run the following commands to create a new project:

$ mkdir ~/dev
$ cd ~/dev
$ newt new myproj
Downloading project skeleton from apache/mynewt-blinky...
Installing skeleton in myproj...
Project myproj successfully created.
$ cd myproj
$ newt upgrade
Downloading repository mynewt-core (commit: master) ...
Downloading repository mynewt-nimble (commit: master) ...
Downloading repository mcuboot (commit: master) ...
Downloading repository mynewt-mcumgr (commit: master) ...
Making the following changes to the project:
apache-mynewt-core successfully upgraded to version 1.7.0
apache-mynewt-nimble successfully upgraded to version 1.2.0
mcuboot successfully upgraded to version 1.3.1

Create the Targets

Create two targets for the RedBear Nano 2 board - one for the bootloader and one for the Blinky application.

Run the following newt target commands, from your project directory, to create a bootloader target. We name the target rbnano2_boot:

$ newt target create rbnano2_boot
$ newt target set rbnano2_boot app=@mcuboot/boot/mynewt
$ newt target set rbnano2_boot bsp=@apache-mynewt-core/hw/bsp/rb-nano2
$ newt target set rbnano2_boot build_profile=optimized

Run the following newt target commands to create a target for the Blinky application. We name the target nrf52_blinky.

$ newt target create rbnano2_blinky
$ newt target set rbnano2_blinky app=apps/blinky
$ newt target set rbnano2_blinky bsp=@apache-mynewt-core/hw/bsp/rb-nano2
$ newt target set rbnano2_blinky build_profile=debug

You can run the newt target show command to verify the target settings:

$ newt target show

Build the Target Executables

Run the newt build rbnano2_boot command to build the bootloader:

$ newt build rbnano2_boot
Building target targets/rbnano2_boot
Compiling repos/mcuboot/boot/bootutil/src/image_rsa.c
Compiling repos/mcuboot/boot/bootutil/src/image_ec256.c
Compiling repos/mcuboot/boot/bootutil/src/loader.c
Compiling repos/apache-mynewt-core/crypto/mbedtls/src/aes.c
Compiling repos/mcuboot/boot/bootutil/src/image_validate.c
Compiling repos/mcuboot/boot/bootutil/src/image_ec.c
Compiling repos/mcuboot/boot/bootutil/src/bootutil_misc.c
Compiling repos/mcuboot/boot/mynewt/src/main.c


Archiving sys_sysinit.a
Archiving util_mem.a
Linking ~/dev/myproj/bin/targets/rbnano2_boot/app/boot/mynewt/mynewt.elf
Target successfully built: targets/rbnano2_boot

Run the newt build rbnano2_blinky command to build the Blinky application:

$ newt build rbnano2_blinky
Building target targets/rbnano2_blinky
Assembling repos/apache-mynewt-core/hw/bsp/rb-nano2/src/arch/cortex_m4/gcc_startup_nrf52_split.s
Compiling repos/apache-mynewt-core/hw/drivers/uart/src/uart.c
Compiling repos/apache-mynewt-core/hw/cmsis-core/src/cmsis_nvic.c
Compiling repos/apache-mynewt-core/hw/bsp/rb-nano2/src/sbrk.c
Compiling apps/blinky/src/main.c


Archiving sys_sysinit.a
Archiving util_mem.a
Linking ~/dev/myproj/bin/targets/rbnano2_blinky/app/apps/blinky/blinky.elf
Target successfully built: targets/rbnano2_blinky

Sign and Create the Blinky Application Image

Run the newt create-image rbnano2_blinky 1.0.0 command to create and sign the application image. You may assign an arbitrary version (e.g. 1.0.0) to the image.

$ newt create-image rbnano2_blinky 1.0.0
App image succesfully generated: ~/dev/myproj/bin/targets/rbnano2_blinky/app/apps/blinky/blinky.img

Connect to the Board

Connect the RedBear Nano 2 USB to a USB port on your computer. You should see an orange LED light up on the board.

Load the Bootloader

Run the newt load rbnano2_boot command to load the bootloader onto the board:

$ newt load rbnano2_boot
Loading bootloader

Note: On Windows platforms, if you get an unable to find CMSIS-DAP device error, you will need to download and install the mbed Windows serial port driver from Follow the instructions from the site to install the driver. Here are some additional notes about the installation:

  1. The instructions indicate that the mbed Windows serial port driver is not required for Windows 10. If you are using Windows 10 and get the unable to find CMSIS-DAP device error, we recommend that you install the driver.

  2. If the driver installation fails, we recommend that you unplug the board, plug it back in, and retry the installation.

Run the newt load rbnano2_boot command again.

Clear the Write Protection on the Flash Memory

The flash memory on the RedBear Nano 2 comes write protected from the factory. If you get an error loading the bootloader and you are using a brand new chip, you need to clear the write protection from the debugger and then load the bootloader again. Run the newt debug rbnano2_blinky command and issue the following commands at the highlighted (gdb) prompts.

Note: The output of the debug session below is for Mac OS and Linux platforms. On Windows, openocd and gdb are started in separate Windows Command Prompt terminals, and the terminals are automatically closed when you quit gdb. In addition, the output of openocd is logged to the openocd.log file in your project’s base directory instead of the terminal.

$ newt debug rbnano2_blinky
[~/dev/myproj/repos/apache-mynewt-core/hw/bsp/rb-nano2/  ~/dev/myproj/repos/apache-mynewt-core/hw/bsp/rb-nano2 ~/dev/myproj/bin/targets/rbnano2_blinky/app/apps/blinky/blinky]
Open On-Chip Debugger 0.10.0-dev-snapshot (2017-03-28-11:24)
Licensed under GNU GPL v2


(gdb) set {unsigned long}0x4001e504=2
(gdb) x/1wx 0x4001e504
(gdb) set {unsigned long}0x4001e50c=1
Info : SWD DPIDR 0x2ba01477
Error: Failed to read memory at 0x00009ef4
(gdb) x/32wx 0x00

Load the Blinky Application Image

Run the newt load rbnano2_blinky command to load the Blinky application image onto the board:

$ newt load rbnano2_blinky
Loading app image into slot 1

You should see a blue LED on the board blink!

Note: If the LED does not blink, try resetting your board.