tests/vcnl40x0: add test application

tests/driver_vcnl40x0/Makefile

+APPLICATION = driver_vcnl40x0
+include ../Makefile.tests_common
+
+USEMODULE += vcnl4010
+USEMODULE += xtimer
+
+include $(RIOTBASE)/Makefile.include

tests/driver_vcnl40x0/README.md

+## About
+This is a test application for the VCNL40X0 proximity and ambient light sensor.
+
+## Usage
+
+After initialization, every 2 seconds, the application:
+* reads the proximity (cts);
+* reads the ambient light (cts);
+* reads the illuminance (computed from ambient light by dividing it by 4);
+* those values are printed to STDOUT.

tests/driver_vcnl40x0/main.c

+/*
+ * Copyright (C) 2017 Inria
+ *
+ * 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
+ * @{
+ *
+ * @file
+ * @brief       Test application for the VNCL40X0 proximity and ambient light sensor.
+ * @author      Alexandre Abadie <alexandre.abadie@inria.fr>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <inttypes.h>
+
+#include "vcnl40x0.h"
+#include "vcnl40x0_params.h"
+#include "xtimer.h"
+#include "board.h"
+
+#define SLEEP_2S   (2U) /* 2 seconds delay between printf */
+
+int main(void)
+{
+    vcnl40x0_t dev;
+    int result;
+
+    puts("VCNL40X0 test application\n");
+
+    printf("+------------Initializing------------+\n");
+    result = vcnl40x0_init(&dev, &vcnl40x0_params[0]);
+    if (result == -VCNL40X0_ERR_I2C) {
+        puts("[Error] The given i2c is not enabled");
+        return 1;
+    }
+    else if (result == -VCNL40X0_ERR_NODEV) {
+        puts("[Error] The sensor did not answer correctly on the given address");
+        return 1;
+    }
+    else {
+        printf("Initialization successful\n\n");
+    }
+
+    printf("\n+--------Starting Measurements--------+\n");
+    while (1) {
+        printf("Proximity [cts]: %d\n"
+               "Ambient light [cts]: %d\n"
+               "Illuminance [lx]: %d\n"
+               "\n+-------------------------------------+\n",
+               vcnl40x0_read_proximity(&dev),
+               vcnl40x0_read_ambient_light(&dev),
+               vcnl40x0_read_illuminance(&dev));
+
+        xtimer_sleep(SLEEP_2S);
+    }
+
+    return 0;
+}