Matrix - 3-Axis Digital Compass
From FriendlyELEC WiKi
Contents
1 Introduction
- The Matrix-3_Axis_Digital_Compass module is designed to measure the direction and functions like to a compass.
- It utilizes the HMC5883L chip. The HMC5883L includes high-resolution HMC118X series magneto-resistive sensors plus an ASIC containing amplification, automatic degaussing strap drivers, offset cancellation, and a 12-bit ADC that enables 1° to 2° compass heading accuracy. It achieves 2 milli-gauss field resolution in ±8 gauss fields. These sensors’ solid-state construction with very low cross-axis sensitivity is designed to measure both the direction and the magnitude of Earth’s magnetic fields, from milli-gauss to 8 gauss. It has an I2C serial bus interface.
- It integrates a 3.3V power conversion IC allowing it to be powered by an external 5V power source. It can be controlled by an I2C master.
2 Features
- I2C，3.3V
- 1° to 2° compass heading accuracy
- 2.54 mm spacing pin
- PCB Dimension(mm): 16 x 16
- Pin Description:
| Pin | Description |
| SDA | I2C SDA |
| SCL | I2C SCL |
| 5V | Supply Voltage 5V |
| GND | Ground |
3 Basic Device Operation
- The Honeywell HMC5883L magnetoresistive sensor circuit is a trio of sensors and application specific support circuits to measure magnetic fields. With power supply applied, the sensor converts any incident magnetic field in the sensitive axis directions to a differential voltage output. The magnetoresistive sensors are made of a nickel-iron (Permalloy) thin-film and patterned as a resistive strip element. In the presence of a magnetic field, a change in the bridge resistive elements causes a corresponding change in voltage across the bridge outputs. These resistive elements are aligned together to have a common sensitive axis (indicated by arrows in the pinout diagram) that will provide positive voltage change with magnetic fields increasing in the sensitive direction. Because the output is only proportional to the magnetic field component along its axis, additional sensor bridges are placed at orthogonal directions to permit accurate measurement of magnetic field in any orientation.
- The HMC5883L communicates via a two-wire I2C bus system as a slave device. It has 8-bit read address and 8-bit write address. This device supports standard and fast modes, 100kHz and 400kHz, respectively, but does not support the high speed mode (Hs). The bus bit format is an 8-bit Data/Address send and a 1-bit acknowledge bit. The format of the data bytes (payload) shall be case sensitive ASCII characters or binary data to the HMC5883L slave, and binary data returned. Negative binary values will be in two’s complement form. The default (factory) HMC5883L 8-bit slave address is 0x3C for write operations, or 0x3D for read operations.
- The module has an I2C interface which complies to the I2C standard protocol and the connection diagram is as follows
4 硬件连接
4.1 连接NanoPi M1
参考下图连接模块：
连接说明：
| Matrix-3_Axis_Digital_Compass | NanoPi M1 |
| SDA | Pin3 |
| SCL | Pin5 |
| 5V | Pin4 |
| GND | Pin6 |
4.2 连接NanoPi 2
参考下图连接模块：
连接说明：
| Matrix-3_Axis_Digital_Compass | NanoPi 2 |
| SDA | Pin3 |
| SCL | Pin5 |
| 5V | Pin4 |
| GND | Pin6 |
4.3 连接NanoPi M2 / NanoPi 2 Fire
NanoPi M2和NanoPi 2 Fire的40 Pin引脚定义是一模一样的，所以它们操作Matrix配件的步骤是一样的，这里仅以NanoPi M2为例。
参考下图连接模块：
连接说明：
| Matrix-3_Axis_Digital_Compass | NanoPi M2 |
| SDA | Pin3 |
| SCL | Pin5 |
| 5V | Pin4 |
| GND | Pin6 |
4.4 连接NanoPC-T2
参考下图连接模块：
Matrix-3_Axis_Digital_Compass_NanoPC-T2
连接说明：
| Matrix-3_Axis_Digital_Compass | NanoPC-T2 |
| SDA | Pin6 |
| SCL | Pin5 |
| 5V | Pin29 |
| GND | Pin30 |
5 Resources
HMC5883L_3-Axis_Digital_Compass_IC.pdf
6 Update Log
6.1 Feb-23-2016
- Added the description for "NanoPi 2 branch" in Section 4
- Added driver's source code location in Section 5.2
