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Introduction:
Not all projects need a cloud connection. Sometimes, you just want to log sensor data locally for later analysis. In this lesson, you’ll learn how to collect environmental sensor readings using the UNIHIKER K10 and save them to a text or CSV file using MicroPython. This feature is ideal for fieldwork, offline logging, or classroom science experiments.

What You’ll Learn:

  • How to open and write to files using MicroPython

  • How to log temperature, humidity, and light data over time

  • How to timestamp your logs using the system clock

  • How to view or export log files later via USB or Thonny

🔧 Step 1: Setup Sensors

python
from pinpong.board import Board from pinpong.libs.unihiker import TempHumSensor, LightSensor import time Board().begin() temp_humi = TempHumSensor() light = LightSensor()

📝 Step 2: Open a File and Write Data

python
# Open or create log file log_file = open("sensor_log.csv", "a") # Use "w" to overwrite instead # Optional: write header row log_file.write("timestamp,temperature,humidity,light\n")

🔁 Step 3: Log Sensor Data with Timestamps

python
while True: timestamp = time.time() temp, humi = temp_humi.read() light_val = light.read() line = f"{timestamp},{temp:.2f},{humi:.2f},{light_val}\n" log_file.write(line) log_file.flush() # Ensure data is saved in real time print("Logged:", line.strip()) time.sleep(5)

You can stop the script anytime using Thonny or by rebooting. Your file sensor_log.csv will appear in the root directory of the device.

💡 Tips for Better Logging

  • Use time.localtime() to convert the timestamp into readable date/time.

  • Rotate files by date (e.g., log_2025_07_24.csv).

  • Visualize the data in Excel, Google Sheets, or Python’s pandas.

Conclusion:
This lesson gives your UNIHIKER K10 the ability to store data locally—perfect for offline environments or battery-powered field sensors. You can combine this with Lesson 3 (Sensor Dashboard) or Lesson 5 (IoT) to offer both live and offline data features. In future lessons, you could schedule logging via button press, add log file selection menus, or even upload logs later when Wi-Fi becomes available.