Matrix - 3-Axis Digital Compass

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1 Introduction

3-Axis Digital Compass
  • 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

重力加速度PCB

  • Pin Description:
Pin Description
SDA I2C SDA
SCL I2C SCL
5V Supply Voltage 5V
GND Ground


3 Download Matrix Source Code

All the matrix modules' code samples are open source. They are maintained on GitHub - https://github.com/friendlyarm/matrix.git
Each branch in this hub contains the matrix modules' code samples for a board that the matrix modules can work with.

  • The nanopi branch contains the matrix modules' code samples for the NanoPi
  • The nanopi 2 branch contains the matrix modules' code samples for the NanoPi 2
  • The tiny4412 branch contains the matrix modules' code samples for the Tiny4412
  • The raspberrypi branch contains the matrix modules' code samples for the RaspberryPi

Please follow the steps below to get the source code:
Install the git utility on a PC running Ubuntu14.04 

$ sudo apt-get install git

Clone the matrix code from GitHub 

$ git clone https://github.com/friendlyarm/matrix.git

If this is successful a "matrix" directory will be generated, which will contain all the matrix modules' code samples.

4 Connect to NanoPi 2

4.1 Hardware Connection

Please refer to the following connection diagram to connect the Matrix-3_Axis_Digital_Compass to the NanoPi 2:
Matrix-3_Axis_Digital_Compass_nanopi_2

Connection Details:

Matrix-3_Axis_Digital_Compass NanoPi 2
SDA Pin3
SCL Pin5
5V Pin4
GND Pin6

4.2 Compile Test Program

Please login the matrix hub and enter the nanopi2 branch 

$ cd matrix
$ git checkout nanopi2

Compile the Matrix code 

$ make CROSS_COMPILE=arm-linux- clean
$ make CROSS_COMPILE=arm-linux-
$ make CROSS_COMPILE=arm-linux- install

Note: please make sure to install the cross compiler "arm-linux-gcc-4.9.3" on your PC, which is used to compile files for the NanoPi 2.
Generated library files are under the "install/lib" directory. The test program is under the "install/usr/bin" directory. The modules are under the "modules" directory.
The modules are under the "modules" directory. The driver's source code is in github: https://github.com/friendlyarm/linux-3.4.y.git


4.3 Run Test Program

Please insert a TF card which is flashed with Debian to a Linux host and mount its boot and rootfs sections.
We assume the rootfs is mounted to /media/rootfs then please run the following commands to copy the module, library and test program to the card.

$ cp modules /media/rootfs/ -r
$ cp install/lib/* /media/rootfs/lib/ -d
$ cp install/usr/bin/* /media/rootfs/usr/bin/

Insert this TF card to your NanoPi 2, power on and run the following command to start the matrix-compass program.

$ matrix-compass

Note: this module is not plug and play therefore before running the module please make sure it is connected to a NanoPi 2.
Here is what you should expect:
matrix-compass_result

4.4 Code Sample

int main(int argc, char ** argv)
{
    int devFD;
    double angle;
 
    if ((devFD = hmc5883Init()) == -1) {
        printf("Fail to init hmc5883\n");
        return -1;
    }
 
    if ((angle = hmc5883Read(devFD)) == -1) {
        printf("Fail to read hmc5883\n");
        hmc5883DeInit(devFD);
        return -1;
    }
    printf("The angle is %f\n", angle);
    printf("You are heading ");
    if((angle < 22.5) || (angle > 337.5 )) {           
        printf("South\n");
    }
    else if((angle > 22.5) && (angle < 67.5 )) {
        printf("South-West\n");
    }
    else if((angle > 67.5) && (angle < 112.5 )) {  
        printf("West\n");
    }
    else if((angle > 112.5) && (angle < 157.5 )) {  
        printf("North-West\n");
    }
    else if((angle > 157.5) && (angle < 202.5 )) {   
        printf("North\n");
    }
    else if((angle > 202.5) && (angle < 247.5 )) {  
        printf("NorthEast\n");
    }
    else if((angle > 247.5) && (angle < 292.5 )) {  
        printf("East\n");
    }
    else if((angle > 292.5) && (angle < 337.5 )) {   
        printf("SouthEast\n");
    }
    hmc5883DeInit(devFD);
    return 0;
}

5 Connect to NanoPi

5.1 Preparations

Please install a Debian on a NanoPi and an appropriate cross compiler on a PC. Please refer to wiki: NanoPi
Compile a NanoPi kernel. Note: please use the kernel's source code from the nanopi-v4.1.y-matrix branch.

$ git clone https://github.com/friendlyarm/linux-4.x.y.git
$ cd linux-4.x.y
$ git checkout nanopi-v4.1.y-matrix
$ make nanopi_defconfig
$ touch .scmversion
$ make

5.2 Hardware Connection

Please refer to the following connection diagram to connect the Matrix-3_Axis_Digital_Compass module to the NanoPi
matrix-3_axis_digital_compass_nanopi

Connection Details:

Matrix-3_Axis_Digital_Compass NanoPi
SDA Pin3
SCL Pin5
5V Pin4
GND Pin6

5.3 Compile Test Program

Please login the matrix hub and enter the nanopi branch 

$ cd matrix
$ git checkout nanopi

Compile the matrix code 

$ make CROSS_COMPILE=arm-linux- clean
$ make CROSS_COMPILE=arm-linux-
$ make CROSS_COMPILE=arm-linux- install

Note: please make sure to install the cross compiler "arm-linux-gcc-4.4.3" on your PC, which is used to compile files for the NanoPi-Debian.
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-3_Axis_Digital_Compass" module is "matrix-compass".

5.4 Run Test Program

Please copy the library files and test program to the NanoPi 

$ cp install/usr/bin/* nanopi_rootfs/usr/bin/
$ cp install/lib/* nanopi_rootfs/lib/ -d

Power on the NanoPi and run the following command in Debian's terminal
Note: this module is not plug and play therefore before running the module please make sure it is connected to a NanoPi. 

$ matrix-3_axis_digital_compass

5.5 Code Sample

int main(int argc, char ** argv)
{
    int devFD;
    double angle;
 
    if ((devFD = hmc5883Init()) == -1) {
        printf("Fail to init hmc5883\n");
        return -1;
    }
 
    if ((angle = hmc5883Read(devFD)) == -1) {
        printf("Fail to read hmc5883\n");
        hmc5883DeInit(devFD);
        return -1;
    }
    printf("The angle is %f\n", angle);
    printf("You are heading ");
    if((angle < 22.5) || (angle > 337.5 )) {           
        printf("South\n");
    }
    else if((angle > 22.5) && (angle < 67.5 )) {
        printf("South-West\n");
    }
    else if((angle > 67.5) && (angle < 112.5 )) {  
        printf("West\n");
    }
    else if((angle > 112.5) && (angle < 157.5 )) {  
        printf("North-West\n");
    }
    else if((angle > 157.5) && (angle < 202.5 )) {   
        printf("North\n");
    }
    else if((angle > 202.5) && (angle < 247.5 )) {  
        printf("NorthEast\n");
    }
    else if((angle > 247.5) && (angle < 292.5 )) {  
        printf("East\n");
    }
    else if((angle > 292.5) && (angle < 337.5 )) {   
        printf("SouthEast\n");
    }
    hmc5883DeInit(devFD);
    return 0;
}

6 Connect to Tiny4412

6.1 Preparations

Please refer to the Tiny4412's user's manual to install a UbuntuCore on the Tiny4412 and install an appropriate cross compiler on a PC.
Note: only the Tiny4412SDK-1506 carrier board can work with this module.

6.2 Hardware Connection

Please refer to the following diagram to connect the Matrix-3_Axis_Digital_Compass to the Tiny4412
matrix-3_axis_digital_compass_tiny4412

Connection Details:

Matrix-3_Axis_Digital_Compass Tiny4412
SDA CON18 SDA
SCL CON18 SCL
5V CON18 5V
GND CON18 GND

6.3 Compile Test Program

Please login the Matrix hub and enter the matrix-tiny4412 branch 

$ cd matrix
$ git checkout tiny4412

Compile the matrix code 

$ make CROSS_COMPILE=arm-linux-gnueabihf- clean
$ make CROSS_COMPILE=arm-linux-gnueabihf-
$ make CROSS_COMPILE=arm-linux-gnueabihf- install

Note: please make sure to install the cross compiler "arm-linux-gnueabihf-gcc-4.7.3" on your PC, which is used to compile files for the Tiny4412-UbuntuCore.
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-3_Axis_Digital_Compass" module is "matrix-compass".

6.4 Run Test Program

Please copy the library files and test program to the Tiny4412 

$ cp install/usr/bin/* tiny4412_rootfs/usr/bin/
$ cp install/lib/* tiny4412_rootfs/lib/ -d

Power on the Tiny4412 and run the following command in UbuntuCore's terminal
Note: this module is not plug and play therefore before running the module please make sure it is connected to a Tiny4412. 

$ matrix-3_axis_digital_compass

6.5 Code Sample

int main(int argc, char ** argv)
{
    int devFD;
    double angle;
 
    if ((devFD = hmc5883Init()) == -1) {
        printf("Fail to init hmc5883\n");
        return -1;
    }
 
    if ((angle = hmc5883Read(devFD)) == -1) {
        printf("Fail to read hmc5883\n");
        hmc5883DeInit(devFD);
        return -1;
    }
    printf("The angle is %f\n", angle);
    printf("You are heading ");
    if((angle < 22.5) || (angle > 337.5 )) {           
        printf("South\n");
    }
    else if((angle > 22.5) && (angle < 67.5 )) {
        printf("South-West\n");
    }
    else if((angle > 67.5) && (angle < 112.5 )) {  
        printf("West\n");
    }
    else if((angle > 112.5) && (angle < 157.5 )) {  
        printf("North-West\n");
    }
    else if((angle > 157.5) && (angle < 202.5 )) {   
        printf("North\n");
    }
    else if((angle > 202.5) && (angle < 247.5 )) {  
        printf("NorthEast\n");
    }
    else if((angle > 247.5) && (angle < 292.5 )) {  
        printf("East\n");
    }
    else if((angle > 292.5) && (angle < 337.5 )) {   
        printf("SouthEast\n");
    }
    hmc5883DeInit(devFD);
    return 0;
}

7 Connect to RaspberryPi

8 Connect to Arduino

9 Resources

HMC5883L_3-Axis_Digital_Compass_IC.pdf

10 Update Log

10.1 Feb-23-2016

  • Added the description for "NanoPi 2 branch" in Section 4
  • Added driver's source code location in Section 5.2
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