How to Use SparkFun OpenLog Serial Data Logger: Examples, Pinouts, and Specs

The SparkFun OpenLog Serial Data Logger (Manufacturer Part ID: DEV-13712) is a compact and versatile data logging module designed to record serial data onto a microSD card. It is an open-source solution that simplifies data collection and analysis from various sensors, microcontrollers, and other serial-enabled devices. With its small form factor and ease of use, the OpenLog is ideal for applications requiring reliable data storage without the need for a computer.

• Logging sensor data from microcontrollers (e.g., Arduino, Raspberry Pi)
• Recording GPS data for navigation and tracking systems
• Storing debugging information during embedded system development
• Collecting data for scientific experiments and research
• Monitoring industrial equipment and processes

The following table outlines the key technical details of the SparkFun OpenLog Serial Data Logger:

The SparkFun OpenLog has a simple pinout for easy integration into your projects. The table below describes each pin:

1. Power the Module: Connect the VCC pin to a 3.3V to 12V power source and the GND pin to ground.
2. Connect Serial Lines:
   • Connect the RXI pin of the OpenLog to the TX pin of your microcontroller or device.
   • Optionally, connect the TXO pin of the OpenLog to the RX pin of your microcontroller for debugging or feedback.
3. Insert a microSD Card: Ensure the microSD card is formatted as FAT16 or FAT32 and insert it into the OpenLog.
4. Configure Baud Rate: The default baud rate is 9600 bps. If needed, you can change it by editing the CONFIG.TXT file on the microSD card.
5. Start Logging: Once powered and connected, the OpenLog will automatically log any serial data received on the RXI pin.

• MicroSD Card Preparation: Always format the microSD card as FAT16 or FAT32 before use. Avoid using cards larger than 32GB.
• Baud Rate Matching: Ensure the baud rate of the OpenLog matches the baud rate of the transmitting device.
• Power Supply: Use a stable power source to avoid data corruption or module malfunction.
• Data Backup: Regularly back up data from the microSD card to prevent loss due to card failure.
• Firmware Updates: Check the SparkFun GitHub repository for firmware updates and enhancements.

Below is an example of how to use the SparkFun OpenLog with an Arduino UNO to log temperature data from a DHT11 sensor:

#include <DHT.h>

// Define DHT sensor pin and type
#define DHTPIN 2
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 bps
  dht.begin();        // Initialize the DHT sensor
  delay(1000);        // Allow sensor to stabilize
}

void loop() {
  float temperature = dht.readTemperature(); // Read temperature in Celsius
  float humidity = dht.readHumidity();       // Read humidity percentage

  // Check if the readings are valid
  if (isnan(temperature) || isnan(humidity)) {
    Serial.println("Failed to read from DHT sensor!");
  } else {
    // Log temperature and humidity to OpenLog
    Serial.print("Temperature: ");
    Serial.print(temperature);
    Serial.print(" C, Humidity: ");
    Serial.print(humidity);
    Serial.println(" %");
  }

  delay(2000); // Wait 2 seconds before the next reading
}

1. No Data Logged on microSD Card

   • Ensure the microSD card is properly inserted and formatted as FAT16 or FAT32.
   • Verify that the OpenLog is receiving serial data on the RXI pin.
   • Check the power supply voltage and current to ensure it meets the module's requirements.

2. Corrupted Data on microSD Card

   • Use a high-quality microSD card to minimize errors.
   • Avoid sudden power loss while the OpenLog is writing data.

3. OpenLog Not Responding

   • Check the connections to the VCC and GND pins.
   • Reset the module by briefly connecting the GRN pin to ground.

4. Baud Rate Mismatch

   • Ensure the baud rate of the transmitting device matches the OpenLog's baud rate.
   • Edit the CONFIG.TXT file on the microSD card to set the desired baud rate.

Q: Can I use the OpenLog with a 5V microcontroller?
A: Yes, the OpenLog is compatible with 5V logic levels, but ensure the power supply voltage is within the 3.3V to 12V range.

Q: How do I change the baud rate?
A: Edit the CONFIG.TXT file on the microSD card and specify the desired baud rate. Save the file and reinsert the card into the OpenLog.

Q: What happens if the microSD card is full?
A: The OpenLog will stop logging data once the card is full. Regularly monitor and clear the card to ensure sufficient storage space.

Q: Can I log data from multiple devices simultaneously?
A: The OpenLog is designed to log data from a single serial source. For multiple devices, consider using a multiplexer or combining data streams programmatically.