Added the basic code

.gitignore

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+.build
+.mbed
+projectfiles
+*.py*
+mbed-os
+BUILD
+

main.cpp

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+#include "mbed.h"
+#include <cstdio>
+
+// The earth's magnetic field varies according to its location.
+// Add or subtract a constant to get the right value
+// of the magnetic field using the following site
+// http://www.ngdc.noaa.gov/geomag-web/#declination
+#define DECLINATION 9.9 // declination (in degrees) in YOUR_LOCATION.
+
+//Functions
+void CMPS2_read_XYZ();
+void CMPS2_init();
+void CMPS2_set(char reset);
+float CMPS2_getHeading();
+void CMPS2_decodeHeading(float measured_angle);
+
+
+I2C i2compass(PB_14, PB_13);
+// I2C slave address
+//const char compasSlaveAddr = 0x30;
+int RWcompasSlaveAddr = 0x60;
+
+char buf[2];
+float Max[2], Mid[2], Min[2], X, Y;     // index 1 : x , index 2 : y or 
+
+
+int main() {
+    /*char testArray[1];
+    for (int i = 0; i<256;i++) {
+        //int rwbitVersion = i << 1;
+        if (i2compass.read(i, testArray,1) == 0){
+            printf("0x%02x ACK\r\n",i);
+        }
+        else{
+            printf("No Slave found with address 0x%x\n", i);
+        }
+    }*/
+
+    i2compass.frequency(400000);
+    // Pmod Compass is init. here
+    ThisThread::sleep_for(500ms);
+    CMPS2_init(); //initialize the compass
+    ThisThread::sleep_for(500ms);
+    printf("sleep ended\n");
+    while (1) {
+
+        printf("%d\n", i2compass.write(RWcompasSlaveAddr, buf, 1));
+        float measured_angle = CMPS2_getHeading();
+        printf("Heading = %f°\t\n", measured_angle);
+        CMPS2_decodeHeading(measured_angle);    //get direction
+        ThisThread::sleep_for(200ms);
+    }
+}
+
+/***********************************
+** Pmod Compass stuff starts here **
+************************************/
+
+//reads measurements in mG
+void CMPS2_read_XYZ(){
+
+    //command internal control register 0 bit 0 (measure)
+    buf[0] = 0x07;
+    buf[1] = 0x01;
+    i2compass.write(RWcompasSlaveAddr, buf, 2);
+    ThisThread::sleep_for(8ms);
+
+    //wait for measurement to be completed
+    bool flag = false;
+    while (!flag) {
+        //jump to status register
+        buf[0] = 0x06;
+        i2compass.write(RWcompasSlaveAddr, buf, 1);
+
+        //read its value
+        i2compass.read(RWcompasSlaveAddr, buf, 1);
+        int temporal = buf[0];
+        //ThisThread::sleep_for(15s);
+        //if the last bit is 1, data is ready
+        temporal &= 1;
+        if (temporal != 0) {
+            flag = true;
+        }
+    }
+    //move address pointer to first address
+    buf[0] = 0x00;
+    i2compass.write(RWcompasSlaveAddr, buf,1);
+    char tmpData[] = {0, 0, 0, 0, 0, 0};
+    i2compass.read(RWcompasSlaveAddr, tmpData, 6);
+
+    //initialize array for data
+    float measured_data[2];  // !!! or measured_data[3] if Z axis is needed
+
+    debug("raw measured data x: %d\n", (tmpData[0] << 8 | tmpData[1]));
+    debug("raw measured data y: %d\n", (tmpData[2] << 8 | tmpData[3]));
+    //reconstruct raw data
+    measured_data[0] = 1.0 * (int) (tmpData[0] << 8 | tmpData[1]); //x
+    measured_data[1] = 1.0 * (int) (tmpData[2] << 8 | tmpData[3]); //y
+    //measured_data[3] = 1.0 * (int) (tmpData[4] << 8 | tmpData[5]); //y    // if Z axis is also included
+
+    // convert raw data to mG
+    for (int i = 0; i < 2; i++) {
+        measured_data[i] = 0.48828125 * (float) measured_data[i];
+    }
+
+    X = measured_data[0];
+    Y = measured_data[1];
+
+    //correct minimum, mid and maximum values
+    if (measured_data[0] > Max[0]) { //X max
+        Max[0] = measured_data[0];
+    }
+    if (measured_data[0] < Min[0]) { //X min
+        Min[0] = measured_data[0];
+    }
+    if (measured_data[1] > Max[1]) { //Y max
+        Max[1] = measured_data[1];
+    }
+    if (measured_data[1] < Min[1]) { //Y min
+        Min[1] = measured_data[1];
+    }
+    /*if (measured_data[2] > Max[2]) { //Z max
+        Max[2] = measured_data[2];
+    }
+    if (measured_data[2] > Max[2]) { //Z max
+        Min[2] = measured_data[2];
+    }*/
+
+    for (int i = 0; i < 2; i++) { //mid
+        Mid[i] = (Max[i] + Min[i]) / 2;
+    }
+
+    // if Z axis is included
+    /*for (int i = 0; i < 3; i++) { //mid
+        Mid[i] = (Max[i] + Min[i]) / 3;
+    }*/
+}
+
+//initialize the compass
+void CMPS2_init(){
+
+    //command internal control register 0 for set operation
+    buf[0] = 0x07;
+    buf[1] = 0x20;
+    i2compass.write(RWcompasSlaveAddr, buf, 2);
+    ThisThread::sleep_for(10ms);
+
+    //command internal control register 1 to 16 bit resolution, 8ms measurement time
+    buf[0] = 0x08;
+    buf[1] = 0x00;
+    i2compass.write(RWcompasSlaveAddr, buf, 2);
+    ThisThread::sleep_for(10ms);
+
+    //initialize minimum, mid and maximum values
+    for (int i = 0; i < 2; i++) { //mid
+        Max[i] = -32768;    //smallest int on 16 bits
+        Min[i] = 32768;     //largest int on 16 bits
+        Mid[i] = 0;
+    }
+
+    // if Z axis is included
+    /*for (int i = 0; i < 3; i++) { //mid
+        Mid[i] = (Max[i] + Min[i]) / 3;
+    }*/
+
+}
+//sets/resets the sensor, changing the magnetic polarity of the sensing element
+void CMPS2_set(char reset){
+
+    //command internal control register 0 bit 7 (capacitor recharge)
+    buf[0] = 0x07;
+    buf[1] = 0x80;
+    i2compass.write(RWcompasSlaveAddr, buf, 2);
+    ThisThread::sleep_for(50ms);
+
+    if (reset) {
+        //command internal control register 0 bit 6 (reset)
+        buf[0] = 0x07;
+        buf[1] = 0x40;
+        i2compass.write(RWcompasSlaveAddr, buf, 2);
+        ThisThread::sleep_for(10ms);
+    }else{
+        //command internal control register 0 bit 5 (set)
+        buf[0] = 0x07;
+        buf[1] = 0x20;
+        i2compass.write(RWcompasSlaveAddr, buf, 2);
+        ThisThread::sleep_for(10ms);
+    }
+}
+float CMPS2_getHeading(){
+
+    float components[2];
+    CMPS2_set(false);  // set the polarity to normal
+    CMPS2_read_XYZ();  // read X, Y, Z components of the magnetic field
+    components[0] = X; // save current results
+    components[1] = Y;
+    CMPS2_set(true);  // set the polarity to normal
+    CMPS2_read_XYZ(); // read X, Y, Z components of the magnetic field
+
+    // eliminate offset from all components
+    components[0] = (components[0] - X) / 2.0;
+    components[1] = (components[1] - Y) / 2.0;
+
+    // variables for storing partial results
+    float temp0 = 0;
+    float temp1 = 0;
+    // and for storing the final result
+    float deg = 0;
+
+    // calculate heading from components of the magnetic field
+    // the formula is different in each quadrant
+    if (components[0] < Mid[0]) {
+        if (components[1] > Mid[1]) {
+        // Quadrant 1
+        temp0 = components[1] - Mid[1];
+        temp1 = Mid[0] - components[0];
+        deg = 90 - atan(temp0 / temp1) * (180 / 3.14159);
+        }
+        else {
+        // Quadrant 2
+        temp0 = Mid[1] - components[1];
+        temp1 = Mid[0] - components[0];
+        deg = 90 + atan(temp0 / temp1) * (180 / 3.14159);
+        }
+    }
+    else{
+        if (components[1] < Mid[1]) {
+        // Quadrant 3
+        temp0 = Mid[1] - components[1];
+        temp1 = components[0] - Mid[0];
+        deg = 270 - atan(temp0 / temp1) * (180 / 3.14159);
+        }
+        else{
+        // Quadrant 4
+        temp0 = components[1] - Mid[1];
+        temp1 = components[0] - Mid[0];
+        deg = 270 + atan(temp0 / temp1) * (180 / 3.14159);
+        }
+    }
+
+    // correct heading
+    deg += DECLINATION;
+    if (DECLINATION > 0) {
+      if (deg > 360) {
+        deg -= 360;
+      }
+    } else {
+      if (deg < 0) {
+        deg += 360;
+      }
+    }
+
+    return deg;
+}
+void CMPS2_decodeHeading(float measured_angle){
+
+    if (measured_angle > 337.25 | measured_angle < 22.5) {
+        printf("North\n");
+    }
+    else if (measured_angle > 292.5) {
+        printf("North-West\n");
+    }
+    else if (measured_angle > 202.5) {
+      printf("South-West\n");
+    }
+    else if (measured_angle > 157.5) {
+      printf("South\n");
+    }
+    else if (measured_angle > 112.5) {
+      printf("South-East\n");
+    }
+    else if (measured_angle > 67.5) {
+      printf("East\n");
+    }
+    else {
+      printf("North-East\n");
+    }
+
+}

mbed-os.lib

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+https://github.com/ARMmbed/mbed-os.git#d147abc3e556c58e5e343d34b729bc2192e18bd3

mbed_app.json

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+{
+    "target_overrides": {
+        "*": {
+            "platform.minimal-printf-enable-floating-point": true,
+            "target.network-default-interface-type": "WIFI",
+            "esp8266.socket-bufsize": "1024",
+            "platform.stdio-buffered-serial": 1,
+            "platform.stdio-convert-newlines": true,
+            "esp8266.provide-default" : false,
+            "target.bootloader_supported"   : true
+        }
+    }
+}