Hi,
First of all I would like to thank you for helping me work through this example. I appreciate your help in getting my to understand why the sparkfun code works but the library doesn't.
I wanted to simplify the bildr code to see where the error is introduced as superficially they do exactly the same thing, i.e., set the mode register to continuous mode, select register 3 and read the 6 bytes of values.
I first tested the bildr select continuous mode function by combining the setup from the bildr code with the loop from the sparkfun code. This worked perfectly so there is no problem with the library constructor or the setMeasurementMode function
#include <Wire.h> //I2C Arduino Library
#include <HMC5883L.h>
#define address 0x1E //0011110b, I2C 7bit address of HMC5883
HMC5883L compass;
void setup()
{
// Initialize the serial port.
Serial.begin(9600);
Wire.begin(); // Start the I2C interface.
compass = HMC5883L(); // Construct a new HMC5883 compass.
Serial.println("Setting measurement mode to continous.");
compass.SetMeasurementMode(Measurement_Continuous); // Set the measurement mode to Continuous
}
void loop() {
int x, y, z; //triple axis data
//Tell the HMC5883 where to begin reading data
Wire.beginTransmission(address);
Wire.write(0x03); //select register 3, X MSB register
Wire.endTransmission();
//Read data from each axis, 2 registers per axis
Wire.requestFrom(address, 6);
if (6 <= Wire.available()) {
x = Wire.read() << 8; //X msb
x |= Wire.read(); //X lsb
z = Wire.read() << 8; //Z msb
z |= Wire.read(); //Z lsb
y = Wire.read() << 8; //Y msb
y |= Wire.read(); //Y lsb
}
//Print out values of each axis
Serial.print("x: ");
Serial.print(x);
Serial.print(" y: ");
Serial.print(y);
Serial.print(" z: ");
Serial.println(z);
delay(250);
}
I then tried to call the readRawAxis function in HMC5883L.cpp as this most closely matched the sparkfun code and it returned fixed values. I then looked inside the ReadRawAxis function to see if it was a problem with the buffer or how it parses the buffer.
MagnetometerRaw HMC5883L::ReadRawAxis()
{
uint8_t* buffer = Read(DataRegisterBegin, 6);
MagnetometerRaw raw = MagnetometerRaw();
raw.XAxis = (buffer[0] << 8) | buffer[1];
raw.ZAxis = (buffer[2] << 8) | buffer[3];
raw.YAxis = (buffer[4] << 8) | buffer[5];
return raw;
}
ReadRawAxis calls the Read function which seems to do exactly what the sparkfun code does. Specify the address you want to read from and then read a specified amount of bytes, which are returned as a pointer to a byte array.
uint8_t* HMC5883L::Read(int address, int length)
{
Wire.beginTransmission(HMC5883L_Address);
Wire.write(address);
Wire.endTransmission();
Wire.beginTransmission(HMC5883L_Address);
Wire.requestFrom(HMC5883L_Address, length);
uint8_t buffer[length];
if(Wire.available() == length)
{
for(uint8_t i = 0; i < length; i++)
{
buffer[i] = Wire.read();
}
}
Wire.endTransmission();
return buffer;
}
I copied the code directly from this to see if the byte array was being populated and it looks like it is not, but this could be a result of me using cpp code in an arduino environment.
I tried pre-specifying a byte array of size 6
byte my_array[6];
my_array = compass.Read(0x03, 6);
but when I call compasss.Read I get the following error:
Arduino: 1.8.1 (Windows 10), Board: "Arduino/Genuino Uno"
C:\Users\umg\Documents\Arduino\hmclibtest\hmclibtest.ino: In function 'void loop()':
hmclibtest:26: error: incompatible types in assignment of 'uint8_t* {aka unsigned char*}' to 'byte [6] {aka unsigned char [6]}'
incompatible types in assignment of 'uint8_t* {aka unsigned char*}' to 'byte [6] {aka unsigned char [6]}'
or when I tried an unsigned char array:
incompatible types in assignment of 'uint8_t* {aka unsigned char*}' to 'unsigned char [6]'
Apologies if I am doing this wrong by mixing cpp and arduino code.
