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Zephyr RTOS and Nordic nRF52-DK: debugging, unit testing, project analysis

By June 30, 2020No Comments

This tutorial originally ran on the PlatformIO docs website. You can find it here. For more content like this, click here.

The goal of this tutorial is to demonstrate how simple it is to use VSCode to develop, run and debug a simple Bluetooth project using Zephyr framework for the Nordic nRF52-DK board.

  • Level: Intermediate
  • Platforms: Windows, Mac OS X, Linux



Setting Up the Project

  1. Click on “PlatformIO Home” button on the bottom PlatformIO Toolbar:../../_images/zephyr-debugging-unit-testing-inspect-1.png
  2. Click on “New Project”, select Nordic nRF52-DK as the development board, Zephyr as the framework and a path to the project location (or use the default one):../../_images/zephyr-debugging-unit-testing-inspect-2.png

Adding Code to the Generated Project

  1. Create a new file main.c in src_dir folder and add the following code:

2. By default Bluetooth feature is disabled, we can enable it by creating a new file prj.conf in zephyr folder and adding the following lines:

Compiling and Uploading the Firmware

  1. To compile the project use one of the following options:
    • Build option from the Project Tasks menu
    • Build button in PlatformIO Toolbar
    • Task Menu Tasks: Run Task... > PlatformIO: Build or in PlatformIO Toolbar
    • Command Palette View: Command Palette > PlatformIO: Build
    • Hotkeys cmd-alt-b / ctrl-alt-b:
  2. If everything went well, we should see a successful result message in the terminal window:../../_images/zephyr-debugging-unit-testing-inspect-4.png
  3. To upload the firmware to the board we can use the following options:
    • Upload option from the Project Tasks menu
    • Upload button in PlatformIO Toolbar
    • Command Palette View: Command Palette > PlatformIO: Upload
    • Task Menu Tasks: Run Task... > PlatformIO: Upload
    • Hotkeys cmd-alt-u / ctrl-alt-u:
  4. Connect the board to your computer and update the default monitor speed to 115200 in platformio.ini file:[env:hifive1-revb] platform = sifive board = hifive1-revb framework = zephyr monitor_speed = 115200
  5. Open Serial Monitor to observe the output from the board:../../_images/zephyr-debugging-unit-testing-inspect-6.png
  6. If everything went well, the board should be visible as a beacon:../../_images/zephyr-debugging-unit-testing-inspect-7.png

Debugging the Firmware

Since Nordic nRF52-DK includes an onboard debug probe we can use PIO Unified Debugger without any configuration.

  1. To start a debug session we can use the following options:
    • Debug: Start debugging from the top menu
    • Start Debugging option from Quick Access menu
    • Hotkey button F5:
  2. We can walk through the code using control buttons, set breakpoints, add variables to Watch window:../../_images/zephyr-debugging-unit-testing-inspect-9.png

Writing Unit Tests


Functions setUp and tearDown are used to initialize and finalize test conditions. Implementations of these functions are not required for running tests but if you need to initialize some variables before you run a test, you use the setUp function and if you need to clean up variables you use tearDown function.

For the sake of simplicity, let’s create a small library called calculator, implement several basic functions addsubmuldiv and test them using PIO Unit Testing engine.

  1. PlatformIO uses a unit testing framework called UnityUnity is not compatible with C library implemented in the framework. Let’s enable standard version of newlib C library in prj.conf file using the following config:CONFIG_NEWLIB_LIBC=y
  2. Create a new folder calculator in the lib folder and add two new files calculator.h and calculator.c with the following contents:calculator.h:#ifndef _CALCULATOR_H_ #define _CALCULATOR_H_ #ifdef __cplusplus extern “C” { #endif int add (int a, int b); int sub (int a, int b); int mul (int a, int b); int div (int a, int b); #ifdef __cplusplus } #endif #endif // _CALCULATOR_H_ calculator.c:#include “calculator.h” int add(int a, int b) { return a + b; } int sub(int a, int b) { return a – b; } int mul(int a, int b) { return a * b; }
  3. Create a new file `test_calc.c to the folder test and add basic tests for calculator library:#include <calculator.h> #include <unity.h> void test_function_calculator_addition(void) { TEST_ASSERT_EQUAL(32, add(25, 7)); } void test_function_calculator_subtraction(void) { TEST_ASSERT_EQUAL(20, sub(23, 3)); } void test_function_calculator_multiplication(void) { TEST_ASSERT_EQUAL(50, mul(25, 2)); } void test_function_calculator_division(void) { TEST_ASSERT_EQUAL(32, div(100, 3)); } void main() { UNITY_BEGIN(); RUN_TEST(test_function_calculator_addition); RUN_TEST(test_function_calculator_subtraction); RUN_TEST(test_function_calculator_multiplication); RUN_TEST(test_function_calculator_division); UNITY_END(); }
  4. Let’s run tests on the board and check the results. There should be a problem with test_function_calculator_division test:../../_images/zephyr-debugging-unit-testing-inspect-10.png
  5. Let’s fix the incorrect expected value, run tests again. After processing the results should be correct:../../_images/zephyr-debugging-unit-testing-inspect-11.png

Project Inspection

For illustrative purposes, let’s imagine we need to find a function with the biggest memory footprint. Also, let’s introduce a bug to our project so PIO Check can report it.

  1. Open PlatformIO Home and navigate to Inspect section, select the current project and press Inspect button:../../_images/zephyr-debugging-unit-testing-inspect-12.png
  2. Project statistics:../../_images/zephyr-debugging-unit-testing-inspect-13.png
  3. The biggest function:../../_images/zephyr-debugging-unit-testing-inspect-14.png
  4. Possible bugs:../../_images/zephyr-debugging-unit-testing-inspect-15.png


Now we have a project template for Nordic Nordic nRF52-DK board that we can use as a boilerplate for the next projects.

Zephyr Project