tests: add hmc5883l driver test

tests/driver_hmc5883l/Makefile

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+include ../Makefile.tests_common
+
+USEMODULE += hmc5883l
+USEMODULE += xtimer
+
+include $(RIOTBASE)/Makefile.include

tests/driver_hmc5883l/README.md

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+# About
+
+Test application for the HMC5883L 3-axis digital compass
+
+# Usage
+
+The test application demonstrates the use of the HMC5883L. It uses the
+default configuration parameters.
+
+- Continuous measurement at a Data Output Rate (DOR) of 15 Hz
+- Normal mode, no biasing
+- Gain 1090 LSB/Gs
+- No averaging of data samples
+
+The application can use different approaches to get new data:
+
+- using the #hmc5883l_read function at a lower rate than the the DOR
+- using the data-ready interrupt (**DRDY**), see #hmc5883l_init_int.
+
+To use the data-ready interrupt (**DRDY**), the application has to enable
+module `hmc5883l_int` and has to configure the GPIO to which the
+interrupt signal is connected. This is done by overrding the default
+configuration parameter `HMC5883L_PARAM_INT_PIN` if necessary, for example:
+
+```
+USEMODULE=hmc5883l_int CFLAGS='-DHMC5883L_PARAM_INT_PIN=GPIO_PIN\(0,12\)' \
+make flash -C tests/driver_hmc5883l BOARD=...
+```
+
+The heading angle is calculated for a magnetic declination in radians defined
+by `HMC5883L_MAG_DECL`. This depends on the current location. The value for
+the current location can be determined at http://www.magnetic-declination.com/.

tests/driver_hmc5883l/main.c

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+/*
+ * Copyright (C) 2018 Gunar Schorcht
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @brief       Test application for the HMC5883L 3-axis digital compass
+ * @author      Gunar Schorcht <gunar@schorcht.net>
+ * @file
+ *
+ * The test application demonstrates the use of the HMC5883L. It uses the
+ * default configuration parameters.
+ *
+ * - Continuous measurement at a Data Output Rate (DOR) of 15 Hz
+ * - Normal mode, no biasing
+ * - Gain 1090 LSB/Gs
+ * - No averaging of data samples
+ *
+ * The application can use different approaches to get new data:
+ *
+ * - using the #hmc5883l_read function at a lower rate than the the DOR
+ * - using the data-ready interrupt (**DRDY**), see #hmc5883l_init_int.
+ *
+ * To use the data-ready interrupt (**DRDY), the application has to enable
+ * module `hmc5883l_int` and has to configure the GPIO to which the
+ * interrupt signal is connected. This is done by overrding the default
+ * configuration parameter `HMC5883L_PARAM_INT_PIN` if necessary, for example:
+ *
+ * ```
+ * USEMODULE=hmc5883l_int CFLAGS='-DHMC5883L_PARAM_INT_PIN=GPIO_PIN\(0,12\)' \
+ * make flash -C tests/driver_hmc5883l BOARD=...
+ * ```
+ *
+ * The heading angle is calculated for a magnetic declination in radians defined
+ * by `HMC5883L_MAG_DECL`. This depends on the current location. The value for
+ * the current location can be determined at http://www.magnetic-declination.com/.
+ */
+
+#include <math.h>
+#include <stdio.h>
+
+#include "thread.h"
+#include "xtimer.h"
+
+#include "hmc5883l.h"
+#include "hmc5883l_params.h"
+
+/*
+ * Magnetic declination in radians according to the real geo location, see:
+ * http://www.magnetic-declination.com/
+ */
+#ifndef HMC5883L_MAG_DECL
+#define HMC5883L_MAG_DECL   (0.0573F)
+#endif
+
+#ifndef M_PI
+#define M_PI    (3.14159265358979323846)
+#endif
+
+#define HMC5883L_SLEEP  (100 * US_PER_MS)
+
+kernel_pid_t p_main;
+
+#if MODULE_HMC5883L_INT
+static void hmc5883l_isr_data_ready (void *arg)
+{
+    (void)arg;
+    /* send a message to trigger main thread to handle the interrupt */
+    msg_t msg;
+    msg_send(&msg, p_main);
+}
+#endif
+
+int main(void)
+{
+    hmc5883l_t dev;
+
+    p_main = sched_active_pid;
+
+    puts("HMC5883L magnetometer driver test application\n");
+    puts("Initializing HMC5883L sensor");
+
+    /* initialize the sensor with default configuration parameters */
+    if (hmc5883l_init(&dev, &hmc5883l_params[0]) == HMC5883L_OK) {
+        puts("[OK]\n");
+    }
+    else {
+        puts("[Failed]");
+        return 1;
+    }
+
+    #if MODULE_HMC5883L_INT
+    /* init INT2/DRDY signal pin and enable the interrupt */
+    hmc5883l_init_int(&dev, hmc5883l_isr_data_ready, 0);
+    #endif /* MODULE_HMC5883L_INT */
+
+    while (1) {
+        #if MODULE_HMC5883L_INT
+        /* wait for data ready interrupt */
+        msg_t msg;
+        msg_receive(&msg);
+        #else
+        /* wait longer than period of HMC5883L DOR */
+        xtimer_usleep(HMC5883L_SLEEP);
+        #endif
+
+        /* read data in any case */
+        hmc5883l_data_t data;
+        if (hmc5883l_read(&dev, &data) == HMC5883L_OK) {
+            /* print xyz data */
+            printf("magn [mGs] x = %" PRIi16 ", y = %" PRIi16 ", z = %" PRIi16 "\n",
+                    data.x, data.y, data.z);
+
+            /* compute and print heading for the given magnetic declination in rad */
+            float head = atan2(data.y, data.x) + HMC5883L_MAG_DECL;
+            if (head < 0) {
+                head += 2 * M_PI;
+            }
+            if (head > 2 * M_PI) {
+                head -= 2 * M_PI;
+            }
+            unsigned deg = head * 180 / M_PI;
+            printf("head [deg] %u\n", deg);
+         }
+    }
+
+    return 0;
+}