How to Use SparkFun OpenLog: Examples, Pinouts, and Specs

The SparkFun OpenLog is an open-source data logger that works over a simple serial connection and supports microSD cards up to 32GB. It is designed to be a straightforward way to log data from sensors, serial devices, or any data source for that matter. The OpenLog provides a simple solution for adding storage to your project and can be used in applications such as weather stations, motion analysis, and event logging systems.

• Data logging for experimental or environmental data
• Serial communication recording
• GPS logging
• Motion or event tracking in robotics
• Long-term data collection for analysis

• Voltage: 3.3V to 12V (regulated to 3.3V)
• Current: 2mA idle, 6mA at maximum recording rate
• Memory: microSD card (FAT16 or FAT32 format, up to 32GB)
• Communication: Serial UART at 9600 bps by default
• Baud Rates: 300 to 1000000 bps (configurable)
• Dimensions: 15mm x 25mm x 4mm

1. Powering the OpenLog: Connect the VCC pin to a power supply between 3.3V and 12V, and connect the GND pin to the ground of your power supply.
2. Connecting to a Microcontroller: Connect the RXI pin of the OpenLog to the TX (transmit) pin of your microcontroller, and the TXO pin to the RX (receive) pin if bidirectional communication is required.
3. Inserting a microSD Card: Insert a formatted microSD card into the OpenLog's card slot.
4. Configuring the Baud Rate: If necessary, configure the OpenLog to match the baud rate of your microcontroller by editing the config.txt file on the microSD card.

• Ensure that the microSD card is formatted correctly before use.
• Avoid removing the microSD card or powering down the system while writing to prevent data corruption.
• For best performance, use a Class 10 microSD card.
• When connecting to a 5V system, ensure that the TXO pin is not directly connected to a 5V RX pin on the microcontroller to avoid damage.

• Data not logging: Ensure the microSD card is properly inserted and formatted. Check the connections and confirm that the OpenLog is powered.
• Garbled data: Verify that the baud rate of the OpenLog matches the baud rate of the connected device.
• OpenLog not responding: Check the power supply and ensure that the voltage is within the specified range.

• If the OpenLog is not creating new files, reformat the microSD card and check the config.txt file for proper settings.
• For communication issues, use a serial monitor to confirm that the OpenLog is outputting the expected startup message.
• In case of file corruption, safely eject the microSD card from the OpenLog before removing it.

#include <SoftwareSerial.h>

SoftwareSerial openLog(2, 3); // RX, TX

void setup() {
  // Start the serial communication
  Serial.begin(9600);
  openLog.begin(9600); // Match the OpenLog's default baud rate
  Serial.println("Initializing OpenLog");

  // Send a command to OpenLog to start a new log file
  openLog.print("new logFile.txt\r");
}

void loop() {
  // Example data to log
  String data = "Temperature: " + String(analogRead(A0));
  
  // Write data to the OpenLog
  openLog.println(data);
  
  // Wait for a second before logging next data point
  delay(1000);
}

Note: The above code assumes that the OpenLog is connected to digital pins 2 and 3 on the Arduino UNO. Adjust the SoftwareSerial pins in the code if you use different pins. Remember to keep the code comments concise and within the 80 character line length limit.