tests/driver_servo: Add test application for drivers/servo

tests/driver_servo/Makefile

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+export APPLICATION = driver_servo
+include ../Makefile.tests_common
+
+FEATURES_REQUIRED = periph_pwm
+
+USEMODULE += vtimer
+USEMODULE += servo
+
+include $(RIOTBASE)/Makefile.include

tests/driver_servo/README.md

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+Background
+==========
+
+Test for the high level servo driver.
+
+Expected result
+===============
+
+A servo connected to `PWM_0` channel 0 should move back and forth inside the
+angle -90 degrees to +90 degrees, approximately.
+
+Using a scope should show a varying pulse length between 1000 us to 2000 us
+long. The requested frequency is 100 Hz, but due to hardware limitations it
+might not be possible to achieve the selected frequency. The pulse width
+should, however, remain the same, only the frequency of pulses (and hence the
+duty cycle) should differ.
+

tests/driver_servo/main.c

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+/*
+ * Copyright (C) 2015 Eistec AB
+ *
+ * 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 servo driver
+ *
+ * This test initializes the given servo device and moves it between
+ * 1.000 -- 2.000 ms, roughly -/+ 90 degrees from the middle position if the
+ * connected servo is a standard RC servo.
+ *
+ * @author      Joakim Gebart <joakim.gebart@eistec.se>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+
+#include "cpu.h"
+#include "board.h"
+#include "vtimer.h"
+#include "periph/pwm.h"
+#include "servo.h"
+
+#define DEV         PWM_0
+#define CHANNEL     0
+
+#define SERVO_MIN        (1000U)
+#define SERVO_MAX        (2000U)
+
+/* these are defined outside the limits of the servo_init min/max parameters above */
+/* we will test the clamping functionality of the servo_set function. */
+#define STEP_LOWER_BOUND (900U)
+#define STEP_UPPER_BOUND (2100U)
+
+/* Step size that we move per WAIT us */
+#define STEP             (10U)
+
+/* Sleep time between updates, no need to update the servo position more than
+ * once per cycle */
+#define WAIT             (10000U)
+
+static servo_t servo;
+
+int main(void)
+{
+    int res;
+    int pos = (STEP_LOWER_BOUND + STEP_UPPER_BOUND) / 2;
+    int step = STEP;
+
+    puts("\nRIOT RC servo test");
+    puts("Connect an RC servo or scope to PWM_0 channel 0 to see anything");
+
+    res = servo_init(&servo, DEV, CHANNEL, SERVO_MIN, SERVO_MAX);
+    if (res < 0) {
+        puts("Errors while initializing servo");
+        return -1;
+    }
+    puts("Servo initialized.");
+
+    while (1) {
+        servo_set(&servo, pos);
+
+        pos += step;
+        if (pos <= STEP_LOWER_BOUND || pos >= STEP_UPPER_BOUND) {
+            step = -step;
+        }
+
+        vtimer_usleep(WAIT);
+    }
+
+    return 0;
+}