tests: added test app for apa102 devices

tests/driver_apa102/Makefile

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+APPLICATION = driver_apa102
+include ../Makefile.tests_common
+
+USEMODULE += apa102
+USEMODULE += color
+USEMODULE += xtimer
+
+include $(RIOTBASE)/Makefile.include

tests/driver_apa102/README.md

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+# About
+This test application is made for verification of the APA102 LED strip driver.
+
+# Usage
+Connect a APA102 based LED strip to a board of your choice, build, and flash
+this application. When run, you should see the strip changing its brightness
+while lighting in red, then green, and then blue. After this sequence, you
+should see a light moving up and down the strip, changing its 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="-DAPA102_PARAM_LED_NUMOF=78"" make all
+```
+
+To change the default pins, simply override the default parameters, e.g.:
+```
+$ CFLAGS="-DAPA102_PARAM_DATA_PIN=GPIO_PIN\(2,3\) -DAPA102_PARAM_CLK_PIN=GPIO_PIN\(1,17\)" make all
+```

tests/driver_apa102/main.c

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+/*
+ * Copyright (C) 2017 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 APA102 LED strip driver
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include <string.h>
+#include <stdio.h>
+#include <stdint.h>
+
+#include "xtimer.h"
+#include "color.h"
+
+#include "apa102.h"
+#include "apa102_params.h"
+
+/**
+ * @brief   Switch to the next LED every 10ms
+ */
+#define STEP        (200 * US_PER_MS)
+
+/**
+ * @brief   Interval for dimming colors
+ */
+#define DIM         (100 * US_PER_MS)
+
+/**
+ * @brief   Step through brightness levels (0-255) in 32 steps
+ */
+#define BSTEP       (8U)
+
+/**
+ * @brief   Allocate the device descriptor
+ */
+static apa102_t dev;
+
+/**
+ * @brief   Allocate a color_rgb_t struct for each LED on the strip
+ */
+static color_rgba_t leds[APA102_PARAM_LED_NUMOF];
+
+static void setcolor(int color, uint8_t alpha)
+{
+    for (int i = 0; i < (int)APA102_PARAM_LED_NUMOF; i++) {
+        leds[i].alpha = alpha;
+        memset(&leds[i].color, 0, sizeof(color_rgb_t));
+        switch (color) {
+            case 0:
+                leds[i].color.r = 255;
+                break;
+            case 1:
+                leds[i].color.g = 255;
+                break;
+            case 2:
+                leds[i].color.b = 255;
+                break;
+        }
+    }
+}
+
+int main(void)
+{
+    int pos = 0;
+    int step = 1;
+    color_hsv_t col = { 0.0, 1.0, 1.0 };
+
+    puts("APA102 Test App");
+
+    /* initialize all LED color values to black (off) */
+    memset(leds, 0, sizeof(color_rgba_t) * APA102_PARAM_LED_NUMOF);
+
+    /* initialize the driver */
+    apa102_init(&dev, &apa102_params[0]);
+
+    puts("Initialization done.");
+
+    /* set to each red, green, and blue, and fade each color in and out */
+    for (int col = 0; col <= 2; col++) {
+        int i = 0;
+        for (; i <= (int)UINT8_MAX; i += BSTEP) {
+            setcolor(col, (uint8_t)i);
+            apa102_load_rgba(&dev, leds);
+            xtimer_usleep(DIM);
+        }
+        i -= BSTEP;
+        for (; i >= 0; i -= BSTEP) {
+            setcolor(col, (uint8_t)i);
+            apa102_load_rgba(&dev, leds);
+            xtimer_usleep(DIM);
+        }
+    }
+
+    puts("Color Fading done");
+
+    /* reset color values */
+    setcolor(-1, 255);
+    apa102_load_rgba(&dev, leds);
+
+    xtimer_ticks32_t now = xtimer_now();
+
+    while (1) {
+        /* change the active color by running around the hue circle */
+        col.h += 1.0;
+        if (col.h > 360.0) {
+            col.h = 0.0;
+        }
+
+        /* set the active LED to the active color value */
+        memset(&leds[pos].color, 0, sizeof(color_rgb_t));
+        pos += step;
+        color_hsv2rgb(&col, &leds[pos].color);
+
+        /* apply the values to the LED strip */
+        apa102_load_rgba(&dev, leds);
+
+        /* switch direction once reaching an end of the strip */
+        if ((pos == (APA102_PARAM_LED_NUMOF - 1)) || (pos == 0)) {
+            step *= -1;
+        }
+
+        xtimer_periodic_wakeup(&now, STEP);
+    }
+
+    return 0;
+}