File content as of revision 0:37dbfb036586:

#include "mbed.h"

#include <string>
#include <array>
#include <iostream>
#include <ratio>
#include <type_traits>

#include <quan/out/magnetic_flux_density.hpp>
#include <quan/three_d/out/vect.hpp>
#include <quan/max.hpp>
#include <quan/min.hpp>

namespace
{
DigitalOut led1(LED1);
} // namespace

/*
 paradigm
   input stream
synchronous/asynchronous
Ideally it updates in background
You can be notified of update in callback
or just read
*/
template<typename SensorUnit>
struct Sensor {
    typedef SensorUnit sensor_unit_t;
    
    // TODO status_t get_status()const;
    virtual bool open() = 0;
    virtual bool read(sensor_unit_t const & current_value) const = 0;
    virtual bool close() = 0;
};

namespace
{
/*
00 Configuration Register A       R/W
01 Configuration Register B       R/W
02 Mode Register                  R/W
03 Data Output X MSB Register     R
04 Data Output X LSB Register     R
05 Data Output Z MSB Register     R
06 Data Output Z LSB Register     R
07 Data Output Y MSB Register     R
08 Data Output Y LSB Register     R
09 Status Register                R
10 Identification Register A      R
11 Identification Register B      R
12 Identification Register C      R
*/

I2C i2c(I2C_SDA, I2C_SCL );
constexpr uint8_t i2c_addr = 0x3D;
constexpr char cfg_regA = 0;
constexpr char cfg_regB = 1;
constexpr char mode_reg = 2;
constexpr char dout_reg = 3;
constexpr char status_reg = 9;
constexpr char id_regA = 10U;

// Set reg index to idx_in
// return true if successful
bool mag_set_reg_idx(uint8_t idx_in)
{
    char const idx = static_cast<char>(idx_in);
    bool const result = (i2c.write(i2c_addr,&idx,1) == 0);
    if(result) {
        return true;
    } else {
        std::cout << "mag_set_reg_idx failed\n";
        return false;
    }
}

// Write reg at idx with val
// return true if successful
bool mag_write_reg(uint8_t idx, uint8_t val)
{
    char ar[2] = {idx,val};
    bool const result = (i2c.write(i2c_addr,ar,2) == 0);
    if(result) {
        return true;
    } else {
        std::cout << " mag_write_reg failed\n";
        return false;
    }
}

// Read reg at idx to result
// return true if successfull
bool mag_get_reg(uint8_t idx_in, uint8_t& result)
{
    if ( mag_set_reg_idx(idx_in)) {
        char result1 = 0;
        if (i2c.read(i2c_addr,&result1,1) == 0) {
            result = result1;
            return true;
        } else {
            std::cout << "mag_get_reg read failed\n";
            return false;
        }
    } else {
        return false;
    }
}

// Update value in reg using and and or masks
// reg <-- (reg & and_val) | or_val
// return true if successfull
bool mag_modify_reg(uint8_t idx, uint8_t and_val, uint8_t or_val)
{
    uint8_t cur_val = 0;
    if(mag_get_reg(idx,cur_val)) {
        uint8_t const new_val = (cur_val & and_val ) | or_val;
        return mag_write_reg(idx,new_val);
    } else {
        return false;
    }
}

// probe for the HMC5883 on I2C
// return true if found
bool mag_detected()
{
    if ( mag_set_reg_idx(id_regA) ) {
        char id_input[4];
        if(i2c.read(i2c_addr,id_input,3) == 0) {
            id_input[3] = '\0';
            bool const is_hmc = (strcmp(id_input,"H43") == 0);
            if (is_hmc) {
                return true;
            } else {
                std::cout << "hmc5883 ID string didnt match\n";
                return false;
            }
        } else {
            std::cout << "id mag read failed\n";
            return false;
        }
    } else {
        return false;
    }
}

// terminal loop, printing message periodically
void loop_forever(std::string const & str)
{
    // stop but print error dynamically
    int count = 0;
    for (;;) {
        led1 = !led1;
        std::cout << str << " " << count++ << '\n';
        ThisThread::sleep_for(1000U);
    }
}

bool mag_set_samples_average(int n_samples)
{
    uint8_t or_val = 0;
    switch (n_samples) {
        case 1 :
            or_val = 0b00U << 5U;
            break;
        case 2 :
            or_val = 0b01U << 5U;
            break;
        case 4 :
            or_val = 0b10U << 5U;
            break;
        case 8 :
            or_val = 0b11U << 5U;
            break;
        default:
            std::cout << "mag_set_samples_average : invalid n_samples (" << n_samples << ")\n";
            return false;
    }
    uint8_t constexpr and_val = ~(0b11 << 5U);
    return mag_modify_reg(cfg_regA,and_val,or_val);
}

/*
data rate 0.75, 1.5, 3 ,7.5, 15 (Default) , 30, 75
*/

namespace detail
{
template <int N, int D=1> struct mag_data_rate_id;
// values are mag settings for each data rate
template <> struct mag_data_rate_id<3,4> : std::integral_constant<uint8_t,(0b000U << 2U)> {};
template <> struct mag_data_rate_id<3,2> : std::integral_constant<uint8_t,(0b001U << 2U)> {};
template <> struct mag_data_rate_id<3> : std::integral_constant<uint8_t,(0b010U << 2U)> {};
template <> struct mag_data_rate_id<15,2> : std::integral_constant<uint8_t,(0b011U << 2U)> {};
template <> struct mag_data_rate_id<15> : std::integral_constant<uint8_t,(0b100U << 2U)> {};
template <> struct mag_data_rate_id<30> : std::integral_constant<uint8_t,(0b101U << 2U)> {};
template <> struct mag_data_rate_id<75> : std::integral_constant<uint8_t,(0b110U << 2U)> {};
} // detail

template <int N, int D=1>
inline bool mag_set_data_rate()
{
    uint8_t constexpr and_val = static_cast<uint8_t>(~(0b111U << 2U));
    uint8_t constexpr or_val = detail::mag_data_rate_id<N,D>::value;
    return mag_modify_reg(cfg_regA,and_val,or_val);
}

bool mag_set_positive_bias()
{
    uint8_t constexpr and_val = static_cast<uint8_t>(~(0b11U ));
    uint8_t constexpr or_val = 0b01U;
    return mag_modify_reg(cfg_regA,and_val,or_val);
}

bool mag_set_negative_bias()
{
    uint8_t constexpr and_val = static_cast<uint8_t>(~(0b11U ));
    uint8_t constexpr or_val = 0b10U;
    return mag_modify_reg(cfg_regA,and_val,or_val);
}

bool mag_clear_bias()
{
    uint8_t constexpr and_val = static_cast<uint8_t>(~(0b11U ));
    uint8_t constexpr or_val = 0b00U;
    return mag_modify_reg(cfg_regA,and_val,or_val);
}

QUAN_QUANTITY_LITERAL(magnetic_flux_density,gauss);
QUAN_QUANTITY_LITERAL(magnetic_flux_density,milli_gauss);
QUAN_QUANTITY_LITERAL(magnetic_flux_density,uT);

// per lsb defualt resolution
quan::magnetic_flux_density::uT mag_resolution = 0.92_milli_gauss;
// range before saturation
quan::magnetic_flux_density::uT mag_range = 1.3_gauss;
// set +- range
// sets the nearest greater equal +-range to abs(range_in)
bool mag_set_range(quan::magnetic_flux_density::uT const & range_in)
{
    uint8_t or_value = 0;
    auto const range = abs(range_in);

    if ( range <= 0.88_gauss) {
        or_value = 0b001U << 5U ;
        mag_range = 0.88_gauss;
        mag_resolution = 0.73_milli_gauss;
    } else if (range <= 1.3_gauss) {
        or_value = 0b001U << 5U ;
        mag_range = 1.3_gauss;
        mag_resolution = 0.92_milli_gauss;
    } else if (range <= 1.9_gauss) {
        or_value = 0b010U << 5U ;
        mag_range = 1.9_gauss;
        mag_resolution = 1.22_milli_gauss;
    } else if (range <= 2.5_gauss) {
        or_value = 0b011U << 5U ;
        mag_range = 2.5_gauss;
        mag_resolution = 1.52_milli_gauss;
    } else if (range <= 4.0_gauss) {
        or_value = 0b100U << 5U ;
        mag_range = 4.0_gauss;
        mag_resolution = 2.27_milli_gauss;
    } else if (range <= 4.7_gauss) {
        or_value = 0b101U << 5U ;
        mag_range = 4.7_gauss;
        mag_resolution = 2.56_milli_gauss;
    } else if (range <=5.6_gauss) {
        or_value = 0b110U << 5U ;
        mag_range = 5.6_gauss;
        mag_resolution = 3.03_milli_gauss;
    } else if ( range <= 8.1_gauss) {
        or_value = 0b111U << 5U ;
        mag_range = 8.1_gauss;
        mag_resolution = 4.35_milli_gauss;
    } else {
        quan::magnetic_flux_density::uT constexpr max_range = 8.1_gauss;
        std::cout << "range too big: max +- range = " << max_range <<"\n";
        return false;
    }
    uint8_t constexpr and_val = static_cast<uint8_t>(~(0b111U << 5U));
    std::cout << "mag range set to : +- " <<  mag_range <<'\n';
    return mag_modify_reg(cfg_regB,and_val,or_value);

}

bool mag_set_continuous_measurement_mode()
{
    uint8_t constexpr and_val = static_cast<uint8_t>(~(0b11U ));
    uint8_t constexpr or_val = 0b00U;
    return mag_modify_reg(mode_reg,and_val,or_val);
}

bool mag_set_single_measurement_mode()
{
    uint8_t constexpr and_val = static_cast<uint8_t>(~(0b11U ));
    uint8_t constexpr or_val = 0b01U;
    return mag_modify_reg(mode_reg,and_val,or_val);
}

bool mag_set_idle_mode()
{
    uint8_t constexpr and_val = static_cast<uint8_t>(~(0b11U ));
    uint8_t constexpr or_val = 0b10U;
    return mag_modify_reg(mode_reg,and_val,or_val);
}

bool mag_data_ready()
{
    uint8_t result = 0;
    if ( mag_get_reg(status_reg, result)) {
        return (result & 0b1U) != 0U;
    } else {
        std::cout << "mag data ready failed\n";
        return false;
    }
}

bool mag_data_locked()
{
    uint8_t result = 0;
    if ( mag_get_reg(status_reg, result)) {
        return (result & 0b10U) != 0U;
    } else {
        std::cout << "mag data locked failed\n";
        return false;
    }
}

// assume mag_data_ready has returned true before call
bool mag_read(quan::three_d::vect<quan::magnetic_flux_density::uT> & v)
{
    if( mag_set_reg_idx(dout_reg)) {
        char arr[7];
        if(i2c.read(i2c_addr,arr,7) == 0) {
            // TODO check status reg arr[6]
            // if
            quan::three_d::vect<int16_t> temp;
            temp.x = static_cast<int16_t>(arr[1]) + ( static_cast<int16_t>(arr[0]) << 8U);
            temp.y = static_cast<int16_t>(arr[5]) + ( static_cast<int16_t>(arr[4]) << 8U);
            temp.z = static_cast<int16_t>(arr[3]) + ( static_cast<int16_t>(arr[2]) << 8U);
            v = temp * mag_resolution;
            return true;
        } else {
            std::cout << "mag_read failed\n";
            return false;
        }
    } else {
        return false;
    }
}

bool mag_do_single_measurement(quan::three_d::vect<quan::magnetic_flux_density::uT>& result)
{
    if ( ! mag_set_single_measurement_mode()) {
        return false;
    }

    while (! mag_data_ready()) {
        ThisThread::sleep_for(5U);
    }
    return mag_read(result);
}

bool mag_get_offsets(quan::three_d::vect<quan::magnetic_flux_density::uT> & result)
{
    // set single measurement mode

    // to prevent saturation
    mag_set_range(5.7_gauss);
    quan::three_d::vect<quan::magnetic_flux_density::uT> mSet;
    // throw away first
    mag_do_single_measurement(mSet);

    mag_set_positive_bias();
    mag_do_single_measurement(mSet);
    std::cout << "mSet = " << mSet <<'\n';

    mag_set_negative_bias();
    quan::three_d::vect<quan::magnetic_flux_density::uT> mReset;
    mag_do_single_measurement(mReset);
    mag_clear_bias();

    std::cout << "mReset = " << mReset <<'\n';

    result = (mSet - mReset )/2;

    std::cout << "result = " << result << '\n';

    return true;
}

}// namespace

int main()
{

    std::cout << "HMC5883 test\n";

    //wait for mag to init
    ThisThread::sleep_for(500U);

    bool success = false;
    if ( mag_detected()) {
        success = true;
        std::cout << "Detected a HMC5883\n";
    } else {
        loop_forever("Failed to detect HMC5883");
    }
    /*

    for ( int i = 0; i < 5; ++i){
        mag_get_offsets(offsets);
        ThisThread::sleep_for(100U);
    }
    */
    // N.b after offsets removed mag was reading around 33.6 uT, so not bad!
    constexpr auto earth_magnetic_field_flux_density = 31.869_uT;

    success =
        mag_set_samples_average(8) &&
        mag_set_data_rate<3,4>() &&
        // N.B if offsets are large then may need to set larger range
        // prob need to cycle through looking for best range
        // so this may not work
        mag_set_range( earth_magnetic_field_flux_density * 2U);

    if ( !success) {
        loop_forever("HMC5883 setup failed");
    }

    // calculate the offsets dynamically by averaging 
    // the min and max over time
    quan::three_d::vect<quan::magnetic_flux_density::uT> voffsets;
    quan::three_d::vect<quan::magnetic_flux_density::uT> vmax;
    quan::three_d::vect<quan::magnetic_flux_density::uT> vmin;

    for (;;) {

        quan::three_d::vect<quan::magnetic_flux_density::uT> values;
        if(mag_do_single_measurement(values)) {

            vmax.x = quan::max(vmax.x,values.x);
            vmax.y = quan::max(vmax.y,values.y);
            vmax.z = quan::max(vmax.z,values.z);

            vmin.x = quan::min(vmin.x,values.x);
            vmin.y = quan::min(vmin.y,values.y);
            vmin.z = quan::min(vmin.z,values.z);

            voffsets = (vmin + vmax)/2.f;

            values -= voffsets;

            std::cout << "val = " << values << '\n';
            std::cout << "off = " << voffsets << "\n\n";
        } else {
            std::cout << "mag read failed\n";
        }
        ThisThread::sleep_for(10U);
    }
}