Setting Up the Project

At first step, we need to create a new project using PlatformIO Home Page (to open this page just press Home icon on the toolbar):

On the next step we need to selectNordicnRF52-DK as a development board,Arduino as a framework and a path to the project location (or use the default one):

Processing the selected project may take some amount of time (PlatformIO will download and install all required packages)and after these steps, we have a fully configured project that is ready for developing code withArduino framework.

Adding Code to the Generated Project

Let’s add some actual code to the project. Firstly, we open a default main filemain.cpp in thesrc_dir folder and replace its contents with the following:

#include<Arduino.h>voidsetup(){pinMode(LED_BUILTIN,OUTPUT);}voidloop(){digitalWrite(LED_BUILTIN,HIGH);delay(100);digitalWrite(LED_BUILTIN,LOW);delay(100);}

After this step, we created a basic blink project ready for compiling and uploading.

Compiling and Uploading the Firmware

Now we can build the project. To compile firmware we can use next options:Build option from theProjectTasks menu, Build button inPlatformIO Toolbar, Task MenuTasks:RunTask...>PlatformIO:Build or inPlatformIO Toolbar, Command PaletteView:CommandPalette>PlatformIO:Build or via hotkeyscmd-alt-b/ctrl-alt-b:

If everything went well, we should see a successful result message in the terminal window:

To upload the firmware to the board we can use next options:Upload option from theProjectTasks menu, Upload button inPlatformIO Toolbar, Command PaletteView:CommandPalette>PlatformIO:Upload, using Task MenuTasks:RunTask...>PlatformIO:Upload or via hotkeyscmd-alt-u/ctrl-alt-u:

After successful uploading, the green LED1 should start blinking.

Debugging the Firmware

Debugging offers the easiest way to debug the board. Firstly, we need to specifydebug_tool in“platformio.ini” (Project Configuration File). Since the board has an on-boardJLink debug probe we can directly declare it in“platformio.ini” (Project Configuration File):

[env:nrf52_dk]platform=nordicnrf52board=nrf52_dkframework=arduinodebug_tool=jlink

To start the debug session we can use next options:Debug:Startdebugging from the top menu,StartDebugging option from Quick Access menu or hotkey buttonF5:

We need to wait some time while PlatformIO is initializing the debug session and when the first line after the main function is highlighted we are ready to debug:

We can walk through the code using control buttons, set breakpoints, add variables toWatchwindow:

Writing Unit Tests

Unit Testing test cases can be added to a single file that may include multiple tests. First of all, in this file, we need to add four default functions:setUp,tearDown,setup andloop. FunctionssetUp andtearDown 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 thesetUp function and if you need to clean up variables you usetearDown function. In our example we will use these functions to accordingly initialize and deinitialize LED.setup andloop functions act as a simple Arduino program where we describe our test plan.

Let’s createtest folder in the root of the project and add a new filetest_main.cpp to this folder. Next basic tests forString class will be implemented in this file:

• test_string_concat tests the concatenation of two strings

• test_string_substring tests the correctness of the substring extraction

• test_string_index_of ensures that the string returns the correct index of the specified symbol

• test_string_equal_ignore_case tests case-insensitive comparison of two strings

• test_string_to_upper_case tests upper-case conversion of the string

• test_string_replace tests the correctness of the replacing operation

#include<Arduino.h>#include<unity.h>StringSTR_TO_TEST;voidsetUp(void){// set stuff up hereSTR_TO_TEST="Hello, world!";}voidtearDown(void){// clean stuff up hereSTR_TO_TEST="";}voidtest_string_concat(void){Stringhello="Hello, ";Stringworld="world!";TEST_ASSERT_EQUAL_STRING(STR_TO_TEST.c_str(),(hello+world).c_str());}voidtest_string_substring(void){TEST_ASSERT_EQUAL_STRING("Hello",STR_TO_TEST.substring(0,5).c_str());}voidtest_string_index_of(void){TEST_ASSERT_EQUAL(7,STR_TO_TEST.indexOf('w'));}voidtest_string_equal_ignore_case(void){TEST_ASSERT_TRUE(STR_TO_TEST.equalsIgnoreCase("HELLO, WORLD!"));}voidtest_string_to_upper_case(void){STR_TO_TEST.toUpperCase();TEST_ASSERT_EQUAL_STRING("HELLO, WORLD!",STR_TO_TEST.c_str());}voidtest_string_replace(void){STR_TO_TEST.replace('!','?');TEST_ASSERT_EQUAL_STRING("Hello, world?",STR_TO_TEST.c_str());}voidsetup(){delay(2000);// service delayUNITY_BEGIN();RUN_TEST(test_string_concat);RUN_TEST(test_string_substring);RUN_TEST(test_string_index_of);RUN_TEST(test_string_equal_ignore_case);RUN_TEST(test_string_to_upper_case);RUN_TEST(test_string_replace);UNITY_END();// stop unit testing}voidloop(){}

Now we are ready to upload tests to the board. To do this we can use next options:Test button onPlatformIO Toolbar, Test option from theProjectTasks menu orTasks:RunTask...>PlatformIOTest from the top menu:

After processing we should see a detailed report about the testing results:

As we can see from the report, all our tests were successful!

Adding Bluetooth LE features

To add the basic BLE functionality to our project we need to define the SoftDevice versionand install a library calledBLEPeripheral.Both these modifications can be specified in“platformio.ini” (Project Configuration File):

[env:nrf52_dk]platform=nordicnrf52board=nrf52_dkframework=arduinodebug_tool=jlink; SoftDevice versionbuild_flags=-DNRF52_S132lib_deps=BLEPeripheral

Now let’s create a basic application that can interact with other BLE devices (e.g phone)For example, next code declares a BLE characteristic that controls the state of the LED1.

#include<Arduino.h>#include<SPI.h>#include<BLEPeripheral.h>BLEPeripheralledPeripheral=BLEPeripheral();BLEServiceledService=BLEService("19b10000e8f2537e4f6cd104768a1214");BLECharCharacteristicledCharacteristic=BLECharCharacteristic("19b10001e8f2537e4f6cd104768a1214",BLERead|BLEWrite);voidsetup(){pinMode(LED_BUILTIN,OUTPUT);ledPeripheral.setAdvertisedServiceUuid(ledService.uuid());ledPeripheral.addAttribute(ledService);ledPeripheral.addAttribute(ledCharacteristic);ledPeripheral.setLocalName("Nordic NRF52 DK");ledPeripheral.begin();}voidloop(){BLECentralcentral=ledPeripheral.central();if(central){while(central.connected()){if(ledCharacteristic.written()){if(ledCharacteristic.value()){digitalWrite(LED_BUILTIN,HIGH);}else{digitalWrite(LED_BUILTIN,LOW);}}}}}

Now we can compile and upload this program to the board as described in previous sections.To verify that our application works as expected, we can use any Android smartphone with BLE feature andNordic nRF Connect tool.

At first, we need to scan all advertising BLE devices and connect to the device calledNordicNRF52DK.After a successful connection to the board, we should see one “Unknown Service” with one “Unknown Characteristic” fields:

To switch the LED on or off we just need write0 or1 asUINT8 to the BLE characteristic:

Conclusion

Now we have a project template for NordicnRF52-DK board that we can use as a boilerplate for the next projects.