Merge pull request #235 from UncleRus/extras/ultrasonic

Driver for ultrasonic range meters + example

examples/ultrasonic/Makefile

@@ -0,0 +1,4 @@
+PROGRAM = ultrasonic
+EXTRA_COMPONENTS = extras/ultrasonic
+
+include ../../common.mk

examples/ultrasonic/main.c

@@ -0,0 +1,60 @@
+/*
+ * Example of using ultrasonic rnaghe meter like HC-SR04
+ *
+ * Part of esp-open-rtos
+ * Copyright (C) 2016 Ruslan V. Uss <unclerus@gmail.com>
+ * BSD Licensed as described in the file LICENSE
+ */
+#include <espressif/esp_common.h>
+#include <esp/uart.h>
+#include <esp/gpio.h>
+#include <ultrasonic/ultrasonic.h>
+
+#define TRIGGER_PIN 5
+#define ECHO_PIN    4
+
+#define MAX_DISTANCE_CM 500 // 5m max
+
+void delay_ms(uint32_t ms)
+{
+    for (uint32_t i = 0; i < ms; i ++)
+        sdk_os_delay_us(1000);
+}
+
+void user_init()
+{
+    uart_set_baud(0, 115200);
+    printf("SDK version : %s\n", sdk_system_get_sdk_version());
+
+    ultrasonic_sensor_t sensor = {
+        .trigger_pin = TRIGGER_PIN,
+        .echo_pin = ECHO_PIN
+    };
+
+    ultrasoinc_init(&sensor);
+
+    while (true)
+    {
+        int32_t distance = ultrasoinc_measure_cm(&sensor, MAX_DISTANCE_CM);
+        if (distance < 0)
+        {
+            printf("Error: ");
+            switch (distance)
+            {
+                case ULTRASONIC_ERROR_PING:
+                    printf("Cannot ping (device is in invalid state)\n");
+                    break;
+                case ULTRASONIC_ERROR_PING_TIMEOUT:
+                    printf("Ping timeout (no device found)\n");
+                    break;
+                case ULTRASONIC_ERROR_ECHO_TIMEOUT:
+                    printf("Echo timeout (i.e. distance too big)\n");
+                    break;
+            }
+        }
+        else
+            printf("Distance: %d cm, %.02f m\n", distance, distance / 100.0);
+
+        delay_ms(200);
+    }
+}