maxsonarez: Initial implementation

The module supports the LV-MaxSonar EZ1, EZ2, EZ3 and EZ4 ultrasonic
range finders.  It was developed and tested on the EZ3 variant.

Signed-off-by: Jon Trulson <jtrulson@ics.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

src/maxsonarez/maxsonarez.cxx

@@ -0,0 +1,58 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <iostream>
+
+#include "maxsonarez.h"
+
+using namespace std;
+using namespace upm;
+
+MAXSONAREZ::MAXSONAREZ(int pin, float aref)
+{
+  if (!(m_aio = mraa_aio_init(pin)))
+    {
+      cerr << __FUNCTION__ << "mraa_aio_init() failed." << endl;
+      return;
+    }
+
+  m_aRes = (1 << mraa_aio_get_bit(m_aio));
+  m_aref = aref;
+
+  // volt's per inch of this sensor
+  m_vI = (m_aref / MAXSONAREZ_RES);
+}
+
+MAXSONAREZ::~MAXSONAREZ()
+{
+  mraa_aio_close(m_aio);
+}
+
+int MAXSONAREZ::inches()
+{
+  int val = mraa_aio_read(m_aio);
+  float volts = float(val) * (m_aref / m_aRes);
+
+  return int(volts / m_vI);
+}