Arduino library for Pololu L3G4200D and L3GD20 boards
Latest commit 192772b Aug 19, 2016 @ryantm ryantm update for library manager

Arduino library for Pololu L3G boards

Version: 3.0.0
Release date: 2016-08-19
Build Status


This is a library for an Arduino-compatible controller that interfaces with L3GD20H, L3GD20, and L3G4200D gyros on Pololu boards. It makes it simple to read the raw gyro data from these boards:

Getting Started


A L3G carrier can be purchased from Pololu's website. Before continuing, careful reading of the product page as well as the chip datasheet is recommended.

Make the following connections with wires between the Arduino and the L3G board:

5V Arduino boards

(including Arduino Uno, Leonardo, Mega; Pololu A-Star 32U4)

Arduino   L3G board
-------   ---------
     5V - VIN
    GND - GND
    SDA - SDA
    SCL - SCL

3.3V Arduino boards

(including Arduino Due)

Arduino   L3G board
-------   ---------
    3V3 - VIN
    GND - GND
    SDA - SDA
    SCL - SCL


If you are using version 1.6.2 or later of the Arduino software (IDE), you can use the Library Manager to install this library:

  1. In the Arduino IDE, open the "Sketch" menu, select "Include Library", then "Manage Libraries...".
  2. Search for "L3G".
  3. Click the L3G entry in the list.
  4. Click "Install".

If this does not work, you can manually install the library:

  1. Download the latest release archive from GitHub and decompress it.
  2. Rename the folder "l3g-arduino-xxxx" to "L3G".
  3. Drag the "L3G" folder into the "libraries" directory inside your Arduino sketchbook directory. You can view your sketchbook location by opening the "File" menu and selecting "Preferences" in the Arduino IDE. If there is not already a "libraries" folder in that location, you should make the folder yourself.
  4. After installing the library, restart the Arduino IDE.

Example program

An example sketch is available that shows how to use the library. You can access it from the Arduino IDE by opening the "File" menu, selecting "Examples", and then selecting "L3G". If you cannot find these examples, the library was probably installed incorrectly and you should retry the installation instructions above.


This program continuously reads the gyro, communicating the readings over the serial interface. You can display the readings with the Arduino Serial Monitor.

Example output:

G X: 188 Y: -10 Z: -47
G X: 138 Y: -40 Z: -26
G X: 110 Y: -55 Z: 4

See the comments in this sketch for some notes on how to convert the raw sensor values to units of dps (degrees per second).

Other library applications

These programs make use of the L3G library but are not included in the library archive or repository.

  • MinIMU-9 + Arduino AHRS
    This sketch allows an Arduino connectd to a MinIMU-9 or AltIMU-10 to function as an attitude and heading reference system, calculating estimated roll, pitch, and yaw angles from sensor readings that can be visualized with a 3D test program on a PC. It is based on the work of Jordi Munoz, William Premerlani, Jose Julio, and Doug Weibel.
  • Pololu_Open_IMU by mikeshub
    This is an alternative AHRS implementation that uses the Madgwick algorithm.
  • ascii_graph by drewtm
    This sketch outputs a text-based graph of LSM303 accelerometer and L3G gyro data, providing a quick way to check whether the sensors are working as expected.


  • vector<int16_t> g
    The last values read from the gyro.
  • byte last_status
    The status of the last I2C transmission. See the Wire.endTransmission() documentation for return values.
  • L3G(void)
  • bool init(byte device, byte sa0)
    Initializes the library with the device being used (device_4200D, device_D20, device_D20H, or device_auto) and the state of the SA0 pin (sa0_low, sa0_high, or sa0_auto), which determines the least significant bit of the I²C slave address. Constants for these arguments are defined in L3G.h. Both of these arguments are optional; if they are not specified, the library will try to automatically detect the device and slave address, and it will return a boolean indicating whether the type of L3G device was successfully determined (if necessary).
  • byte getDeviceType(void)
    Returns the device type specified to or detected by init().
  • void enableDefault(void)
    Turns on the gyro and enables a consistent set of default settings. This function will set the gyro's full scale to be +/-250 dps (degrees per second), which means that a reading of 114 corresponds to approximately 1 dps. See the comments in L3G.cpp for a full explanation of these settings.
  • void writeReg(byte reg, byte value)
    Writes a gyro register with the given value. Register address constants are defined by the regAddr enumeration type in L3G.h. Example use: gyro.writeReg(L3G::CTRL_REG1, 0x6F);
  • byte readReg(byte reg)
    Reads a gyro register and returns the value read.
  • void read(void)
    Takes a reading from the gyro and stores the values in the vector g.
  • void setTimeout(unsigned int timeout)
    Sets a timeout period for read(), in milliseconds, after which it will abort if no data is received. A value of 0 disables the timeout.
  • unsigned int getTimeout(void)
    Returns the current timeout period setting.
  • bool timeoutOccurred(void)
    Returns a boolean indicating whether a call to read() has timed out since the last call to timeoutOccurred().

Version history

  • 3.0.0 (2016-08-19): Updated library to work with the Arduino Library Manager.
  • 2.0.0 (2015-02-05): Major rewrite, making library more consistent with LSM303 library. List of significant changes:
    • enableDefault() behavior changed to be more explicit and consistent across devices.
    • Library constants converted to enums.
    • L3GD20H is now detected as a distinct device (instead of being treated as an L3GD20) and constants have been added for the register names specified in its datasheet.
    • Added timeout functions from LSM303 library.
  • 1.2.2 (2014-02-05): Added support for L3GD20H.
  • 1.2.1 (2012-10-31): Cast sensor readings to 16-bit ints for better portability.
  • 1.2.0 (2012-07-06): Renamed library to L3G and added support for L3GD20.
    • Besides the name change, the main difference from the L3G4200D library as originally released is that you need to call the init() function before using any of the other library functions, typically from within the Arduino setup() function. While the older library only works with the Pololu boards' default gyro slave address of 1101001b, the new library allows you to specify the slave address with the init() function.
  • 1.1.0 (2011-12-12): Arduino 1.0 compatibility.
  • 1.0.0 (2011-09-14): Original release of L3G4200D library.