tests: added test for low-level PWM driver

tests/periph_pwm/Makefile

@@ -0,0 +1,11 @@
+export APPLICATION = periph_pwm
+include ../Makefile.tests_common
+
+BOARD_BLACKLIST := chronos mbed_lpc1768 msb-430 msb-430h native qemu-i386 redbee-econotag telosb \
+                   wsn430-v1_3b wsn430-v1_4 z1
+# all listed boards: no periph_conf.h defined,
+
+USEMODULE += vtimer
+DISABLE_MODULE += auto_init
+
+include $(RIOTBASE)/Makefile.include

tests/periph_pwm/README.md

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+Expected result
+===============
+If everything is running as supposed to, you should see a 1KHz PWM with oscillating duty cycle
+on each channel of the selected PWM device.
+
+Background
+==========
+Test for the low-level PWM driver.

tests/periph_pwm/main.c

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+/*
+ * Copyright (C) 2014 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 for low-level PWM drivers
+ *
+ * This test initializes the given PWM device to run at 1KHz with a 1000 step resolution.
+ *
+ * The PWM is then continuously oscillating it's duty cycle between 0% to 100% every 1s on
+ * every channel.
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+
+#include "cpu.h"
+#include "board.h"
+#include "vtimer.h"
+#include "periph/pwm.h"
+
+/* only compile this test if PWM devices are defined */
+#if PWM_NUMOF
+
+#define WAIT        (10000)
+#define STEP        (10)
+
+#define DEV         PWM_0
+#define CHANNELS    PWM_0_CHANNELS
+#define MODE        PWM_LEFT
+
+#define FREQU       (1000U)
+#define STEPS       (1000U)
+
+
+int main(void)
+{
+    int res;
+    int state = 0;
+    int step = STEP;
+
+    puts("\nRIOT PWM test");
+    puts("Connect an LED or scope to PWM pins to see something\n");
+
+    res = pwm_init(DEV, MODE, FREQU, STEPS);
+    if (res == 0) {
+        puts("PWM successfully initialized.\n");
+    }
+    else {
+        puts("Errors while initializing PWM");
+        return -1;
+    }
+
+    while (1) {
+        for (int i = 0; i < CHANNELS; i++) {
+            pwm_set(DEV, i, state);
+        }
+
+        state += step;
+        if (state <= 0 || state >= STEPS) {
+            step = -step;
+        }
+
+        vtimer_usleep(WAIT);
+    }
+
+    return 0;
+}
+
+#else
+
+int main(void)
+{
+    puts("\nRIOT PWM test");
+    puts("There are no PWM devices defined for this board!");
+
+    return 0;
+}
+
+#endif /* PWM_NUMOF */