Teensy 4.1 with QMC6310 Magnetometer to USB MIDI

Overview

The QMC6310 magnetometer sensor outputs 16 bit for each axis X, Y and Z. The code uses the Wire library to communicate via the I2C protocol. This example prints the raw axis values to the serial monitor and also sends as a USB MIDI control change message (scaled to 0 - 127). The datasheet for this sensor can be found here. 

Hardware

The following connections should be made between the Teensy 4.1 and the QMC6310:

• Teensy 4.1 3V to QMC6310 VCC - orange in the above photo
• Teensy 4.1 ground to QMC6310 GND - blue in the above photo
• Teensy 4.1 pin 19 / A5 / SCL / PWM to QMC6310 SCL - green in the above photo
• Teensy 4.1 pin 18 / A4 / SDA / PWM to QMC6310 SDA - yellow in the above photo

Software

const int address = 0x1c; // 0x1c if part number is QMC6310U or 0x3c if part number is QMC6310N

int16_t axis[3]; // array for axis data X, Y, Z - force 2's compliment for a signed 16 bit integer

#include <Wire.h>

void setup() {

// Begin serial port

Serial.begin(57600);

Serial.println("Begin...");

// Begin Wire library

Wire.begin();

// set up magnetometer

// writeMag(0x29, 0x06); // define sign for XYZ

writeMag(0x0b, 0x00 | 0x01 << 2); // define set / reset on

// field range: 2gauss = 0x11 << 2, 8gauss = 0x10 << 2, 12gauss = 0x01 << 2, 30guass = 0x00 << 2

writeMag(0x0a, 0xcd); // set normal range and ODR to 200 Hz

}

void loop() {

if (readMag()) { // if there is new data present, print the values of the three axis as a sixteen bit value

Serial.print("X: ");

Serial.print(axis[0]);

usbMIDI.sendControlChange(1, map(axis[0], -32768, 32767, 0, 127), 1);

Serial.print(" Y: ");

Serial.print(axis[1]);

usbMIDI.sendControlChange(2, map(axis[1], -32768, 32767, 0, 127), 1);

Serial.print(" Z: ");

Serial.println(axis[2]);

usbMIDI.sendControlChange(3, map(axis[2], -32768, 32767, 0, 127), 1);

}

}

// this function writes data to the magnetometer

void writeMag(byte reg, byte val) {

Wire.beginTransmission(address);

Wire.write(reg);

Wire.write(val);

Wire.endTransmission();

}

// this function reads X,Y,Z data from the magnetometer

int readMag() {

// set reg 9 to read from

Wire.beginTransmission(address);

Wire.write(0x09);

Wire.endTransmission();

// read from reg 9 for 1 byte - this is the status byte

byte status; // status byte which stores the

Wire.requestFrom(address, 1);

while (Wire.available()) {

status = Wire.read() & 1;

}

if (status == true) {

// set reg 1 to read from

Wire.beginTransmission(address);

Wire.write(0x01);

Wire.endTransmission();

// read from reg 9 for 6 bytes - these are the data bytes X LSB, X HSB, Y LSB, Y HSB, Z LSB, Z HSB

Wire.requestFrom(address, 0x06);

byte index = 0;

// read data into axis array

while (Wire.available()) {

axis[index] = Wire.read() | Wire.read() << 8;

index++;

}

return true; // true if new data is present

}

else {

return false; // false if no new data is present

}

}