hmc5883l: C port; FTI; C++ wraps C

Signed-off-by: Jon Trulson <jtrulson@ics.com>

examples/c++/hmc5883l.cxx

@@ -32,16 +32,17 @@ main(int argc, char **argv)
 //! [Interesting]
     // Instantiate on I2C
     upm::Hmc5883l* compass = new upm::Hmc5883l(0);
-    int16_t *pos;
 
-    compass->set_declination(0.2749); // Set your declination from true north in radians
+    compass->set_declination(0.2749); // Set your declination from
+                                      // true north in radians
 
     // Print out the coordinates, heading, and direction every second
     while(true){
         compass->update(); // Update the coordinates
-        pos = compass->coordinates();
+        const int16_t *pos = compass->coordinates();
         fprintf(stdout, "coor: %5d %5d %5d ", pos[0], pos[1], pos[2]);
-        fprintf(stdout, "heading: %5.2f direction: %3.2f\n", compass->heading(), compass->direction());
+        fprintf(stdout, "heading: %5.2f direction: %3.2f\n",
+                compass->heading(), compass->direction());
         sleep(1);
     }
 //! [Interesting]

examples/c/CMakeLists.txt

@@ -145,6 +145,7 @@ add_example (mcp2515)
 add_example (max30100)
 add_example (speaker)
 add_example (cjq4435)
+add_example (hmc5883l)
 
 # Custom examples
 add_custom_example (nmea_gps_i2c-example-c nmea_gps_i2c.c nmea_gps)

examples/c/hmc5883l.c

@@ -0,0 +1,82 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * Ported based on original C++ code by:
+ * Author: Brendan Le Foll <brendan.le.foll@intel.com>
+ * Contributions: Mihai Tudor Panu <mihai.tudor.panu@intel.com>
+ * Copyright (c) 2014 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <signal.h>
+
+#include <upm_utilities.h>
+
+#include "hmc5883l.h"
+
+bool shouldRun = true;
+
+void sig_handler(int signo)
+{
+  if (signo == SIGINT)
+    shouldRun = false;
+}
+
+int main(int argc, char **argv)
+{
+    signal(SIGINT, sig_handler);
+
+//! [Interesting]
+    // Instantiate an HMC8883L on I2C bus 0
+    hmc5883l_context sensor = hmc5883l_init(0);
+
+    if (!sensor)
+    {
+        printf("%s: hmc5883l_init() failed\n", __FUNCTION__);
+        return 1;
+    }
+
+    hmc5883l_set_declination(sensor, 0.2749); // Set your declination
+                                              // from true north in
+                                              // radians
+
+    // Print out the coordinates, heading, and direction every second
+    while (shouldRun)
+    {
+        hmc5883l_update(sensor); // Update the coordinates
+        const int16_t *pos = hmc5883l_coordinates(sensor);
+
+        printf("coor: %5d %5d %5d ", pos[0], pos[1], pos[2]);
+        printf("heading: %5.2f direction: %3.2f\n",
+               hmc5883l_heading(sensor), hmc5883l_direction(sensor));
+
+        upm_delay(1);
+    }
+
+    hmc5883l_close(sensor);
+
+//! [Interesting]
+
+    return 0;
+}

include/fti/upm_compass.h

@@ -0,0 +1,43 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#ifndef UPM_COMPASS_H_
+#define UPM_COMPASS_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Compass function table
+typedef struct _upm_compass_ft {
+    upm_result_t (*upm_compass_set_scale) (void* dev, float scale);
+    upm_result_t (*upm_compass_set_offset) (void* dev, float offset);
+    // returns a heading in degrees
+    upm_result_t (*upm_compass_get_value) (void* dev, float *value);
+} upm_compass_ft;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* UPM_COMPASS_H_ */

include/upm_fti.h

@@ -125,6 +125,7 @@ typedef struct _upm_sensor_ft* (*func_get_upm_sensor_ft)(upm_sensor_t sensor_typ
 #include <fti/upm_binary.h>
 #include <fti/upm_rotaryencoder.h>
 #include <fti/upm_pressure.h>
+#include <fti/upm_compass.h>
 
 #ifdef __cplusplus
 }

src/hmc5883l/CMakeLists.txt

@@ -1,5 +1,11 @@
-set (libname "hmc5883l")
-set (libdescription "Digital Compass")
-set (module_src ${libname}.cxx)
-set (module_hpp ${libname}.hpp)
-upm_module_init()
+upm_mixed_module_init (NAME hmc5883l
+    DESCRIPTION "3-axis Digital Compass"
+    C_HDR hmc5883l.h
+    C_SRC hmc5883l.c
+    CPP_HDR hmc5883l.hpp
+    CPP_SRC hmc5883l.cxx
+    CPP_WRAPS_C
+    FTI_SRC hmc5883l_fti.c
+    REQUIRES mraa)
+
+target_link_libraries(${libnamec} m)

src/hmc5883l/hmc5883l.c

@@ -0,0 +1,246 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * Ported based on original C++ code by:
+ * Author: Brendan Le Foll <brendan.le.foll@intel.com>
+ * Contributions: Mihai Tudor Panu <mihai.tudor.panu@intel.com>
+ * Copyright (c) 2014 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <string.h>
+#include <stdio.h>
+#include <assert.h>
+
+#include "math.h"
+#include "hmc5883l.h"
+
+#define MAX_BUFFER_LENGTH 6
+#define HMC5883L_I2C_ADDR 0x1E
+
+// configuration registers
+#define HMC5883L_CONF_REG_A 0x00
+#define HMC5883L_CONF_REG_B 0x01
+
+// mode register
+#define HMC5883L_MODE_REG 0x02
+
+// data register
+#define HMC5883L_X_MSB_REG 0
+#define HMC5883L_X_LSB_REG 1
+#define HMC5883L_Z_MSB_REG 2
+#define HMC5883L_Z_LSB_REG 3
+#define HMC5883L_Y_MSB_REG 4
+#define HMC5883L_Y_LSB_REG 5
+#define DATA_REG_SIZE 6
+
+// status register
+#define HMC5883L_STATUS_REG 0x09
+
+// ID registers
+#define HMC5883L_ID_A_REG 0x0A
+#define HMC5883L_ID_B_REG 0x0B
+#define HMC5883L_ID_C_REG 0x0C
+
+// mode
+#define HMC5883L_CONT_MODE 0x00
+// start of data registers (MSB/LSB for X, Z, and Y axis)
+#define HMC5883L_DATA_REG 0x03
+
+// scales
+#define GA_0_88_REG 0x00 << 5
+#define GA_1_3_REG 0x01 << 5
+#define GA_1_9_REG 0x02 << 5
+#define GA_2_5_REG 0x03 << 5
+#define GA_4_0_REG 0x04 << 5
+#define GA_4_7_REG 0x05 << 5
+#define GA_5_6_REG 0x06 << 5
+#define GA_8_1_REG 0x07 << 5
+
+// scale factors
+#define SCALE_0_73_MG 0.73
+#define SCALE_0_92_MG 0.92
+#define SCALE_1_22_MG 1.22
+#define SCALE_1_52_MG 1.52
+#define SCALE_2_27_MG 2.27
+#define SCALE_2_56_MG 2.56
+#define SCALE_3_03_MG 3.03
+#define SCALE_4_35_MG 4.35
+
+hmc5883l_context hmc5883l_init(int bus)
+{
+    // make sure MRAA is initialized
+    int mraa_rv;
+    if ((mraa_rv = mraa_init()) != MRAA_SUCCESS)
+    {
+        printf("%s: mraa_init() failed (%d).\n", __FUNCTION__, mraa_rv);
+        return NULL;
+    }
+
+    hmc5883l_context dev =
+        (hmc5883l_context)malloc(sizeof(struct _hmc5883l_context));
+
+    if (!dev)
+        return NULL;
+
+    // zero out context
+    memset((void *)dev, 0, sizeof(struct _hmc5883l_context));
+
+    if (!(dev->i2c = mraa_i2c_init(bus)))
+    {
+        printf("%s: mraa_i2c_init() failed.\n", __FUNCTION__);
+        hmc5883l_close(dev);
+        return NULL;
+    }
+
+    // apparently only one address supported...
+    if (mraa_i2c_address(dev->i2c, HMC5883L_I2C_ADDR))
+    {
+        printf("%s: mraa_i2c_address() failed.\n", __FUNCTION__);
+        hmc5883l_close(dev);
+        return NULL;
+    }
+
+    // I guess we only support a single configuration...
+    uint8_t buf[2];
+
+    buf[0] = HMC5883L_CONF_REG_B;
+    buf[1] = GA_1_3_REG; // should be 1.2 according to DS
+    if (mraa_i2c_write(dev->i2c, buf, 2))
+    {
+        printf("%s: mraa_i2c_write(HMC5883L_CONF_REG_B) failed.\n",
+               __FUNCTION__);
+        hmc5883l_close(dev);
+        return NULL;
+    }
+
+    // ... and we only support continuous mode.
+    buf[0] = HMC5883L_MODE_REG;
+    buf[1] = HMC5883L_CONT_MODE;
+    if (mraa_i2c_write(dev->i2c, buf, 2))
+    {
+        printf("%s: mraa_i2c_write(HMC5883L_MODE_REG) failed.\n",
+               __FUNCTION__);
+        hmc5883l_close(dev);
+        return NULL;
+    }
+
+    // do an initial update
+    if (hmc5883l_update(dev))
+    {
+        printf("%s: hmc5883l_update() failed.\n", __FUNCTION__);
+        hmc5883l_close(dev);
+        return NULL;
+    }
+
+    return dev;
+}
+
+void hmc5883l_close(hmc5883l_context dev)
+{
+    assert(dev != NULL);
+
+    if (dev->i2c)
+        mraa_i2c_stop(dev->i2c);
+
+    free(dev);
+}
+
+upm_result_t hmc5883l_update(const hmc5883l_context dev)
+{
+    assert(dev != NULL);
+
+    // set device reg address
+    if (mraa_i2c_write_byte(dev->i2c, HMC5883L_DATA_REG))
+    {
+        printf("%s: mraa_i2c_write_byte(HMC5883L_DATA_REG) failed.\n",
+               __FUNCTION__);
+        return UPM_ERROR_OPERATION_FAILED;
+    }
+
+    uint8_t buf[DATA_REG_SIZE];
+
+    // now read the data (6 bytes)
+    int rb;
+    if ((rb = mraa_i2c_read(dev->i2c, buf, DATA_REG_SIZE)) != DATA_REG_SIZE)
+    {
+        printf("%s: mraa_i2c_read() failed.  Got %d bytes, expected %d.\n",
+               __FUNCTION__, rb, DATA_REG_SIZE);
+        return UPM_ERROR_OPERATION_FAILED;
+    }
+
+    // The device stores the data in X, Z, Y order, however, we
+    // store them in X, Y, Z order.
+
+    // x
+    dev->coords[0] = (buf[HMC5883L_X_MSB_REG] << 8 )
+        | buf[HMC5883L_X_LSB_REG];
+    // z
+    dev->coords[2] = (buf[HMC5883L_Z_MSB_REG] << 8 )
+        | buf[HMC5883L_Z_LSB_REG];
+    // y
+    dev->coords[1] = (buf[HMC5883L_Y_MSB_REG] << 8 )
+        | buf[HMC5883L_Y_LSB_REG];
+
+    return UPM_SUCCESS;
+}
+
+float hmc5883l_direction(const hmc5883l_context dev)
+{
+    assert(dev != NULL);
+
+    // we seem to only support a single scale :(
+    return atan2(dev->coords[1] * SCALE_0_92_MG,
+                 dev->coords[0] * SCALE_0_92_MG) + dev->declination;
+}
+
+float hmc5883l_heading(const hmc5883l_context dev)
+{
+    assert(dev != NULL);
+
+    float dir = hmc5883l_direction(dev) * 180/M_PI;
+    if (dir < 0)
+        dir += 360.0;
+
+    return dir;
+}
+
+const int16_t *hmc5883l_coordinates(const hmc5883l_context dev)
+{
+    assert(dev != NULL);
+
+    return dev->coords;
+}
+
+void hmc5883l_set_declination(const hmc5883l_context dev, float dec)
+{
+    assert(dev != NULL);
+
+    dev->declination = dec;
+}
+
+float hmc5883l_get_declination(const hmc5883l_context dev)
+{
+    assert(dev != NULL);
+
+    return dev->declination;
+}

src/hmc5883l/hmc5883l.cxx

@@ -1,4 +1,8 @@
 /*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * Ported based on original C++ code by:
  * Author: Brendan Le Foll <brendan.le.foll@intel.com>
  * Contributions: Mihai Tudor Panu <mihai.tudor.panu@intel.com>
  * Copyright (c) 2014 Intel Corporation.
@@ -26,146 +30,52 @@
 #include <string>
 #include <stdexcept>
 
-#include "math.h"
 #include "hmc5883l.hpp"
 
-#define MAX_BUFFER_LENGTH 6
-#define HMC5883L_I2C_ADDR 0x1E
-
-//configuration registers
-#define HMC5883L_CONF_REG_A 0x00
-#define HMC5883L_CONF_REG_B 0x01
-
-//mode register
-#define HMC5883L_MODE_REG 0x02
-
-//data register
-#define HMC5883L_X_MSB_REG 0
-#define HMC5883L_X_LSB_REG 1
-#define HMC5883L_Z_MSB_REG 2
-#define HMC5883L_Z_LSB_REG 3
-#define HMC5883L_Y_MSB_REG 4
-#define HMC5883L_Y_LSB_REG 5
-#define DATA_REG_SIZE 6
-
-//status register
-#define HMC5883L_STATUS_REG 0x09
-
-//ID registers
-#define HMC5883L_ID_A_REG 0x0A
-#define HMC5883L_ID_B_REG 0x0B
-#define HMC5883L_ID_C_REG 0x0C
-
-#define HMC5883L_CONT_MODE 0x00
-#define HMC5883L_DATA_REG 0x03
-
-//scales
-#define GA_0_88_REG 0x00 << 5
-#define GA_1_3_REG 0x01 << 5
-#define GA_1_9_REG 0x02 << 5
-#define GA_2_5_REG 0x03 << 5
-#define GA_4_0_REG 0x04 << 5
-#define GA_4_7_REG 0x05 << 5
-#define GA_5_6_REG 0x06 << 5
-#define GA_8_1_REG 0x07 << 5
-
-//digital resolutions
-#define SCALE_0_73_MG 0.73
-#define SCALE_0_92_MG 0.92
-#define SCALE_1_22_MG 1.22
-#define SCALE_1_52_MG 1.52
-#define SCALE_2_27_MG 2.27
-#define SCALE_2_56_MG 2.56
-#define SCALE_3_03_MG 3.03
-#define SCALE_4_35_MG 4.35
 
 using namespace upm;
+using namespace std;
 
-Hmc5883l::Hmc5883l(int bus) : m_i2c(bus)
+Hmc5883l::Hmc5883l(int bus) :
+    m_hmc5883l(hmc5883l_init(bus))
 {
-    mraa::Result error;
-    error = m_i2c.address(HMC5883L_I2C_ADDR);
-    if(error != mraa::SUCCESS){
-        throw std::invalid_argument(std::string(__FUNCTION__) +
-                                    ": i2c.address() failed");
-        return;
-    }
-    m_rx_tx_buf[0] = HMC5883L_CONF_REG_B;
-    m_rx_tx_buf[1] = GA_1_3_REG;
-    error = m_i2c.write(m_rx_tx_buf, 2);
-    if(error != mraa::SUCCESS){
-        throw std::runtime_error(std::string(__FUNCTION__) +
-                                    ": i2c.write() configuration failed");
-        return;
-    }
-
-    error = m_i2c.address(HMC5883L_I2C_ADDR);
-    if(error != mraa::SUCCESS){
-        throw std::invalid_argument(std::string(__FUNCTION__) +
-                                    ": i2c.address() failed");
-        return;
-    }
-    m_rx_tx_buf[0] = HMC5883L_MODE_REG;
-    m_rx_tx_buf[1] = HMC5883L_CONT_MODE;
-    error = m_i2c.write(m_rx_tx_buf, 2);
-    if(error != mraa::SUCCESS){
-        throw std::runtime_error(std::string(__FUNCTION__) +
-                                    ": i2c.write() mode failed");
-        return;
-    }
-
-    Hmc5883l::update();
+    if (!m_hmc5883l)
+        throw std::runtime_error(string(__FUNCTION__)
+                                 + ": hmc5883l_init() failed");
 }
 
-mraa::Result
-Hmc5883l::update(void)
+upm_result_t Hmc5883l::update(void)
 {
-    m_i2c.address(HMC5883L_I2C_ADDR);
-    m_i2c.writeByte(HMC5883L_DATA_REG);
+    if (hmc5883l_update(m_hmc5883l))
+        throw std::runtime_error(string(__FUNCTION__)
+                                 + ": hmc5883l_update() failed");
 
-    m_i2c.address(HMC5883L_I2C_ADDR);
-    m_i2c.read(m_rx_tx_buf, DATA_REG_SIZE);
-
-    // x
-    m_coor[0] = (m_rx_tx_buf[HMC5883L_X_MSB_REG] << 8 ) | m_rx_tx_buf[HMC5883L_X_LSB_REG];
-    // z
-    m_coor[2] = (m_rx_tx_buf[HMC5883L_Z_MSB_REG] << 8 ) | m_rx_tx_buf[HMC5883L_Z_LSB_REG];
-    // y
-    m_coor[1] = (m_rx_tx_buf[HMC5883L_Y_MSB_REG] << 8 ) | m_rx_tx_buf[HMC5883L_Y_LSB_REG];
-
-    return mraa::SUCCESS;
+    // kind of pointless, but want to maintain some compatibility with
+    // original code.
+    return UPM_SUCCESS;
 }
 
-float
-Hmc5883l::direction(void)
+float Hmc5883l::direction(void)
 {
-    return atan2(m_coor[1] * SCALE_0_92_MG, m_coor[0] * SCALE_0_92_MG) + m_declination;
+    return hmc5883l_direction(m_hmc5883l);
 }
 
-float
-Hmc5883l::heading(void)
+float Hmc5883l::heading(void)
 {
-    float dir = Hmc5883l::direction() * 180/M_PI;
-    if(dir < 0){
-        dir += 360.0;
-    }
-    return dir;
+    return hmc5883l_heading(m_hmc5883l);
 }
 
-int16_t*
-Hmc5883l::coordinates(void)
+const int16_t *Hmc5883l::coordinates(void)
 {
-    return &m_coor[0];
+    return hmc5883l_coordinates(m_hmc5883l);
 }
 
-void
-Hmc5883l::set_declination(float dec)
+void Hmc5883l::set_declination(float dec)
 {
-    m_declination = dec;
+    return hmc5883l_set_declination(m_hmc5883l, dec);
 }
 
-float
-Hmc5883l::get_declination()
+float Hmc5883l::get_declination()
 {
-    return m_declination;
+    return hmc5883l_get_declination(m_hmc5883l);
 }

src/hmc5883l/hmc5883l.h

@@ -0,0 +1,132 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * Ported based on original C++ code by:
+ * Author: Brendan Le Foll <brendan.le.foll@intel.com>
+ * Contributions: Mihai Tudor Panu <mihai.tudor.panu@intel.com>
+ * Copyright (c) 2014 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#pragma once
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <upm.h>
+#include <mraa/i2c.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+    /**
+     * @file hmc5883l.h
+     * @library hmc5883l
+     * @brief HMC5883L 3-Axis Digital Compass
+     *
+     */
+
+    /**
+     * Device context
+     */
+    typedef struct _hmc5883l_context {
+        mraa_i2c_context i2c;
+
+        int16_t coords[3];
+        float   declination;
+    } *hmc5883l_context;
+
+
+    /**
+     * Initialize an Hmc5883l device
+     *
+     * @param bus Number of the used I2C bus
+     * @return Device context, or NULL on error
+     */
+    hmc5883l_context hmc5883l_init(int bus);
+
+    /**
+     * Close the device
+     *
+     * @param Device context
+     */
+    void hmc5883l_close(hmc5883l_context dev);
+
+    /**
+     * Updates the values by reading from I2C
+     *
+     * @param Device context
+     * @return UPM result
+     */
+    upm_result_t hmc5883l_update(const hmc5883l_context dev);
+
+    /*
+     * Returns the direction.  hmc5883l_update() must have been called
+     * prior to calling this function.
+     *
+     * @param Device context
+     * @return Direction
+     */
+    float hmc5883l_direction(const hmc5883l_context dev);
+
+    /*
+     * Returns the heading.  hmc5883l_update() must have been called
+     * prior to calling this function.
+     *
+     * @param Device context
+     * @return Heading
+     */
+    float hmc5883l_heading(const hmc5883l_context dev);
+
+    /**
+     * Returns a pointer to an int[3] that contains the coordinates as
+     * integers.  hmc5883l_update() must have been called prior to calling
+     * this function.
+     *
+     * @param Device context
+     * @return *int to an int[3] (X, Y, Z)
+     */
+    const int16_t *hmc5883l_coordinates(const hmc5883l_context dev);
+
+    /**
+     * Sets the magnetic declination for better accuracy.
+     * hmc5883l_update() must have been called prior to calling this
+     * function.
+     *
+     * @param Device context
+     * @param dec The magnetic declination
+     */
+    void hmc5883l_set_declination(const hmc5883l_context dev, float dec);
+
+    /**
+     * Gets the current magnetic declination value.  hmc5883l_update()
+     * must have been called prior to calling this function.
+     *
+     * @param Device context
+     * @return Magnetic declination as a floating-point value
+     */
+    float hmc5883l_get_declination(const hmc5883l_context dev);
+
+#ifdef __cplusplus
+}
+#endif

src/hmc5883l/hmc5883l.hpp

@@ -1,4 +1,8 @@
 /*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * Ported based on original C++ code by:
  * Author: Brendan Le Foll <brendan.le.foll@intel.com>
  * Contributions: Mihai Tudor Panu <mihai.tudor.panu@intel.com>
  * Copyright (c) 2014 Intel Corporation.
@@ -24,19 +28,17 @@
  */
 #pragma once
 
-#include <mraa/i2c.hpp>
-
-#define MAX_BUFFER_LENGTH 6
+#include "hmc5883l.h"
 
 namespace upm {
 
-/**
+    /**
      * @brief HMC5883L Magnometer library
      * @defgroup hmc5883l libupm-hmc5883l
      * @ingroup seeed i2c compass robok
      */
 
-/**
+    /**
      * @library hmc5883l
      * @sensor hmc5883l
      * @comname HMC5883L 3-Axis Digital Compass
@@ -50,19 +52,21 @@ namespace upm {
      *
      * Honeywell [HMC5883L]
      * (http://www.adafruit.com/datasheets/HMC5883L_3-Axis_Digital_Compass_IC.pdf)
- * is a 3-axis digital compass. Communication with HMC5883L is simple and
- * all done through an I2C interface. Different breakout boards are available.
- * Typically, a 3V supply is all that is needed to power the sensor.
+     * is a 3-axis digital compass. Communication with HMC5883L is
+     * simple and all done through an I2C interface. Different
+     * breakout boards are available.  Typically, a 3V supply is all
+     * that is needed to power the sensor.
      *
      * @image html hmc5883l.jpeg
      * @snippet hmc5883l.cxx Interesting
      */
-class Hmc5883l {
-public:
+    class Hmc5883l {
+    public:
         /**
-     * Creates an Hmc5883l object
+         * Creates an Hmc5883l object. The I2C address cannot be
+         * changed, and is always 0x1e (7-bit).
          *
-     * @param bus Number of the used I2C bus
+         * @param bus I2C bus number
          */
         Hmc5883l(int bus);
 
@@ -81,14 +85,14 @@ public:
          *
          * @return *int to an int[3]
          */
-    int16_t* coordinates();
+        const int16_t* coordinates();
 
         /**
          * Updates the values by reading from I2C
          *
          * @return 0 if successful
          */
-    mraa::Result update();
+        upm_result_t update();
 
         /**
          * Sets the magnetic declination for better calibration
@@ -101,11 +105,10 @@ public:
          * @return Magnetic declination as a floating-point value
          */
         float get_declination();
-private:
-    int16_t m_coor[3];
-    float m_declination;
-    uint8_t m_rx_tx_buf[MAX_BUFFER_LENGTH];
-    mraa::I2c m_i2c;
-};
 
+    protected:
+        hmc5883l_context m_hmc5883l;
+
+    private:
+    };
 }

src/hmc5883l/hmc5883l_fti.c

@@ -0,0 +1,87 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include "hmc5883l.h"
+#include "upm_fti.h"
+
+/**
+ * This file implements the Function Table Interface (FTI) for this sensor
+ */
+
+const char upm_hmc5883l_name[] = "HMC5883L";
+const char upm_hmc5883l_description[] = "HMC5883L Compass";
+const upm_protocol_t upm_hmc5883l_protocol[] = {UPM_I2C};
+const upm_sensor_t upm_hmc5883l_category[] = {UPM_COMPASS};
+
+// forward declarations
+const void* upm_hmc5883l_get_ft(upm_sensor_t sensor_type);
+void* upm_hmc5883l_init_name();
+void upm_hmc5883l_close(void *dev);
+upm_result_t upm_hmc5883l_get_heading(void *dev, float *value);
+
+static const upm_sensor_ft ft =
+{
+  .upm_sensor_init_name = upm_hmc5883l_init_name,
+  .upm_sensor_close = upm_hmc5883l_close,
+};
+
+static const upm_compass_ft cft =
+{
+  .upm_compass_get_value = upm_hmc5883l_get_heading,
+};
+
+const void* upm_hmc5883l_get_ft(upm_sensor_t sensor_type)
+{
+  switch(sensor_type)
+    {
+    case UPM_SENSOR:
+      return &ft;
+    case UPM_COMPASS:
+      return &cft;
+    default:
+      return NULL;
+    }
+}
+
+void* upm_hmc5883l_init_name()
+{
+  return NULL;
+}
+
+void upm_hmc5883l_close(void *dev)
+{
+  hmc5883l_close((hmc5883l_context)dev);
+}
+
+upm_result_t upm_hmc5883l_get_heading(void *dev, float *value)
+{
+  upm_result_t rv;
+
+  if ((rv = hmc5883l_update((hmc5883l_context)dev)))
+    return rv;
+
+  *value = hmc5883l_heading((hmc5883l_context)dev);
+
+  return UPM_SUCCESS;
+}