tests: added test for the LPD8808 driver

tests/driver_lpd8808/Makefile

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+APPLICATION = driver_lpd8808
+include ../Makefile.tests_common
+
+USEMODULE += lpd8808
+USEMODULE += xtimer
+
+include $(RIOTBASE)/Makefile.include

tests/driver_lpd8808/README.md

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+# About
+This test application is made for verification of the LPD8808 LED strip driver.
+
+# Usage
+Connect a LPD8808 based LED strip to a board of your choice, build, and flash
+this application. You should see a light running up and down your strip,
+slowly changing it's color.
+
+You might need to adjust the default parameters (number of LEDs on the strip and
+pin configuration). You can do this simply by pre-setting the `CFLAGS`
+environment variable, e.g.:
+```
+$ CFLAGS="-DLPD8808_PARAM_LED_CNT=78"" make all
+```

tests/driver_lpd8808/main.c

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+/*
+ * Copyright (C) 2016 Freie Universität Berlin
+ *
+ * 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 LPD8808 LED strip driver
+ *
+ * Refer to the accompanying README.md for more information.
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include <string.h>
+#include <stdio.h>
+
+#include "xtimer.h"
+
+#include "lpd8808.h"
+#include "lpd8808_params.h"
+
+/**
+ * @brief   Switch to the next LED every 10ms
+ */
+#define STEP        (10 * 1000U)
+
+/**
+ * @brief   Allocate the device descriptor
+ */
+static lpd8808_t dev;
+
+/**
+ * @brief   Allocate a color_rgb_t struct for each LED on the strip
+ */
+static color_rgb_t leds[LPD8808_PARAM_LED_CNT];
+
+
+int main(void)
+{
+    uint32_t now = xtimer_now();
+    int pos = 0;
+    int step = 1;
+    color_hsv_t col = { 0.0, 1.0, 1.0 };
+
+    /* initialize all LED color values to black (off) */
+    memset(leds, 0, sizeof(color_rgb_t) * LPD8808_PARAM_LED_CNT);
+
+    /* initialize the driver */
+    lpd8808_init(&dev, &lpd8808_params[0]);
+
+    while (1) {
+
+        /* change the active color by running around the hue circle */
+        col.h += 1.0;
+        if (col.h > 360.0) {
+            col.h = 0;
+        }
+
+        /* set the active LED to the active color value */
+        memset(&leds[pos], 0, sizeof(color_rgb_t));
+        pos += step;
+        color_hsv2rgb(&col, &leds[pos]);
+
+        /* apply the values to the LED strip */
+        lpd8808_load_rgb(&dev, leds);
+
+        /* switch direction once reaching an end of the strip */
+        if ((pos == (LPD8808_PARAM_LED_CNT - 1)) || (pos == 0)) {
+            step *= -1;
+        }
+
+        xtimer_periodic_wakeup(&now, STEP);
+    }
+
+    return 0;
+}