GY-271 Magnetoresistive Electronic Compass Module – 3-Axis, 3–5V, I2C

The GY-271 Electronic compass module is a compact three-axis magnetoresistive sensor module designed to measure the Earth's magnetic field on the X, Y, and Z axes and calculate a compass heading. It is one of the most widely used electronic compass modules in the Arduino and Raspberry Pi ecosystem, valued for its low cost, I²C interface, and straightforward library support. The module is typically populated with either the Honeywell HMC5883L or the pin-compatible QMC5883L magnetoresistive sensor, depending on the production batch and supplier.

The sensing element uses anisotropic magnetoresistive (AMR) technology: a thin-film permalloy material changes its electrical resistance in response to an applied magnetic field. This resistance change is converted by an integrated ASIC—which includes amplification, offset cancellation, and a 12-bit analog-to-digital converter—into a digital value that corresponds to the magnetic field strength along each axis. The result is a heading accuracy of approximately 1° to 2°, with a measurement range of ±1.3 to ±8 Gauss and a resolution of roughly 2 milligauss (5 milligauss per the SunFounder listing). The sensor supports data rates of up to 160Hz, making it suitable for dynamic orientation tracking as well as static compass readings.

The module operates from a 3V to 5V supply and communicates over I²C. The HMC5883L variant uses the fixed I²C address 0x1E, while the QMC5883L variant uses 0x0D (or 0x0C on some boards). The board includes 10kΩ pull-up resistors on the I²C lines and a level shifter so that the 3.3V sensor core can be connected safely to 5V microcontrollers. A DRDY (data ready) pin is also exposed for high-speed data streaming. The module measures approximately 14 × 13 × 4mm (with slight variations between suppliers) and is a passive sensor breakout—it does not include a display, battery, or enclosure.