tests/srf04: test application for srf04 driver

tests/driver_srf04/Makefile

+include ../Makefile.tests_common
+
+BOARD ?= nrf52dk
+
+RIOTBASE ?= $(CURDIR)/../..
+
+USEMODULE += srf04
+
+include $(RIOTBASE)/Makefile.include

tests/driver_srf04/README.md

+tests/driver_srf04
+================
+This example shows the usage of an srf04 module.
+The application uses a timer and two gpio pins.
+The module is an ultrasonic range finder with a small protocol [1]:
+- trigger pin is raised high for 10 us by calling trigger function
+- after a sample period of 50 ms the value can be read out
+
+[1] www.robot-electronics.co.uk/htm/srf04tech.htm
+
+Usage
+=====
+
+Build, flash and start the application:
+
+    export BOARD=your_board
+    make flash term

tests/driver_srf04/main.c

+/*
+ * Copyright (C) 2018 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 srf04 ultra sonic range finder driver
+ *
+ * @author      Semjon Kerner <semjon.kerner@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "srf04_params.h"
+#include "srf04.h"
+
+int main(void)
+{
+    puts("SRF04 range finder example");
+
+    srf04_t dev;
+    if (srf04_init(&dev, &srf04_params[0]) != SRF04_OK) {
+        puts("Error: initializing");
+        return 1;
+    }
+
+    while (1) {
+        int distance = srf04_get_distance(&dev);
+        if (distance < SRF04_OK) {
+            puts("Error: no valid data available");
+        } else {
+            printf("D: %d mm\n", distance);
+        }
+    }
+
+    return 0;
+}