Integrate I2C Temperature Sensor with Zephyr on nRF52840 Development Kit

Introduction

Integrating an I2C temperature sensor with the Zephyr RTOS on the nRF52840 Development Kit is a straightforward process that can enhance the functionality of your project. This tutorial will guide you through the steps to add the sensor using Device Tree overlays, ensuring proper configuration and communication.

Prerequisites

• Basic knowledge of C programming
• Familiarity with Zephyr RTOS
• nRF52840 Development Kit
• Installed toolchain for Zephyr development
• Access to a compatible I2C temperature sensor (e.g., TMP102)

Parts/Tools

• nRF52840 Development Kit
• I2C temperature sensor (e.g., TMP102)
• Connecting wires
• Computer with Zephyr SDK installed
• J-Link debugger (optional)

Steps

1. Connect the Sensor
   1. Connect the VCC pin of the sensor to the 3.3V pin on the nRF52840.
   2. Connect the GND pin of the sensor to the GND pin on the nRF52840.
   3. Connect the SDA pin of the sensor to the SDA pin (typically P0.26).
   4. Connect the SCL pin of the sensor to the SCL pin (typically P0.27).
2. Create a New Zephyr Project
   1. Navigate to your Zephyr workspace directory:

   cd ~/zephyrproject/zephyr/samples

   2. Copy an existing sample to create your own:

   cp -r hello_world my_temp_sensor

   3. Change to your new project directory:

   cd my_temp_sensor

3. Create a Device Tree Overlay
   1. Create a new file named my_temp_sensor.overlay in your project folder.
   2. Add the following content to configure the I2C temperature sensor:

   
   &i2c0 {
       temp_sensor: tmp102@48 {
           compatible = "ti,tmp102";
           reg = ;
           label = "TMP102";
       };
   };
               

4. Modify the CMakeLists.txt
   1. Open CMakeLists.txt in your project folder.
   2. Add the following line to include the overlay:

   zephyr_overlay_file(my_temp_sensor.overlay)

5. Implement the Temperature Reading Logic
   1. Open src/main.c and include the necessary headers:

   
   #include 
   #include 
   #include 
               

   2. Initialize the logging library:

   
   LOG_MODULE_REGISTER(my_temp_sensor);
               

   3. Implement the main function to read the temperature:

   
   void main(void) {
       const struct device *dev = device_get_binding("TMP102");
       struct sensor_value temp;
   
       if (dev == NULL) {
           LOG_ERR("Failed to get binding for TMP102");
           return;
       }
   
       while (1) {
           sensor_sample_fetch(dev);
           sensor_channel_get(dev, SENSOR_CHAN_AMBIENT_TEMP, &temp);
           LOG_INF("Temperature: %d.%06d C", temp.val1, temp.val2);
           k_sleep(K_MSEC(1000));
       }
   }
               

6. Build and Flash the Project
   1. Navigate to your project directory:

   cd ~/zephyrproject/zephyr/samples/my_temp_sensor

   2. Build the project:

   west build -b nrf52840dk_nrf52840

   3. Flash the project onto the nRF52840:

   west flash

Troubleshooting

• Device Not Found: Ensure the sensor is properly connected and powered. Check the I2C address in the overlay.
• Build Errors: Verify that the Device Tree overlay file is correctly named and included in CMakeLists.txt.
• Sensor Readings Not Accurate: Double-check sensor connections and ensure it’s calibrated if necessary.

Conclusion

By following these steps, you have successfully integrated an I2C temperature sensor with the nRF52840 Development Kit using Zephyr’s Device Tree overlays. This setup can serve as a foundation for more complex sensor-based applications. Happy coding!