a110x: Add interrupt support and a suitable example

Signed-off-by: Jon Trulson <jtrulson@ics.com>
Signed-off-by: John Van Drasek <john.r.van.drasek@intel.com>

examples/c++/CMakeLists.txt

@@ -104,6 +104,7 @@ add_executable (adafruitms1438-example adafruitms1438.cxx)
 add_executable (adafruitms1438-stepper-example adafruitms1438-stepper.cxx)
 add_executable (hx711-example hx711.cxx)
 add_executable (flex-example flex.cxx)
+add_executable (a110x-intr-example a110x-intr.cxx)
 
 include_directories (${PROJECT_SOURCE_DIR}/src/hmc5883l)
 include_directories (${PROJECT_SOURCE_DIR}/src/grove)
@@ -293,3 +294,4 @@ target_link_libraries (adafruitms1438-example adafruitms1438 ${CMAKE_THREAD_LIBS
 target_link_libraries (adafruitms1438-stepper-example adafruitms1438 ${CMAKE_THREAD_LIBS_INIT})
 target_link_libraries (hx711-example hx711 ${CMAKE_THREAD_LIBS_INIT})
 target_link_libraries (flex-example flex ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries (a110x-intr-example a110x ${CMAKE_THREAD_LIBS_INIT})

examples/c++/a110x-intr.cxx

@@ -0,0 +1,76 @@
+/*
+ * 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 <unistd.h>
+#include <iostream>
+#include <signal.h>
+#include "a110x.h"
+
+using namespace std;
+
+int shouldRun = true;
+
+void sig_handler(int signo)
+{
+  if (signo == SIGINT)
+    shouldRun = false;
+}
+
+// Our pulse counter
+volatile unsigned int counter = 0;
+
+// Our interrupt handler
+void hallISR(void *arg)
+{
+  counter++;
+}
+
+int main ()
+{
+  signal(SIGINT, sig_handler);
+
+//! [Interesting]
+  // Instantiate an A110X sensor on digital pin D2
+  upm::A110X* hall = new upm::A110X(2);
+  
+  // This example uses a user-supplied interrupt handler to count
+  // pulses that occur when a magnetic field of the correct polarity
+  // is detected.  This could be used to measure the rotations per
+  // minute (RPM) of a rotor for example.
+
+  hall->installISR(hallISR, NULL);
+
+  while (shouldRun)
+    {
+      cout << "Pulses detected: " << counter << endl;
+
+      sleep(1);
+    }
+//! [Interesting]
+
+  cout << "Exiting..." << endl;
+
+  delete hall;
+  return 0;
+}

src/a110x/a110x.cxx

@@ -31,8 +31,6 @@ using namespace std;
 
 A110X::A110X(int pin)
 {
-  mraa_init();
-
   if ( !(m_gpio = mraa_gpio_init(pin)) )
     {
       cerr << __FUNCTION__ << ": mraa_gpio_init() failed" << endl;
@@ -40,10 +38,14 @@ A110X::A110X(int pin)
     }
 
   mraa_gpio_dir(m_gpio, MRAA_GPIO_IN);
+  m_isrInstalled = false;
 }
 
 A110X::~A110X()
 {
+  if (m_isrInstalled)
+    uninstallISR();
+
   mraa_gpio_close(m_gpio);
 }
 
@@ -52,3 +54,19 @@ bool A110X::magnetDetected()
   return (!mraa_gpio_read(m_gpio) ? true : false);
 }
 
+void A110X::installISR(void (*isr)(void *), void *arg)
+{
+  if (m_isrInstalled)
+    uninstallISR();
+
+  // install our interrupt handler
+  mraa_gpio_isr(m_gpio, MRAA_GPIO_EDGE_FALLING, 
+                isr, arg);
+  m_isrInstalled = true;
+}
+
+void A110X::uninstallISR()
+{
+  mraa_gpio_isr_exit(m_gpio);
+  m_isrInstalled = false;
+}

src/a110x/a110x.h

@@ -50,7 +50,10 @@ namespace upm {
    * whether it is detecting a magnetic field with south polarity
    * perpendicular to the sensor element.
    *
+   * An example showing a simple test for the presence of a field
    * @snippet a110x.cxx Interesting
+   * An example demonstrating the use of an interrupt handler to count pulses
+   * @snippet a110x-intr.cxx Interesting
    */
   class A110X {
   public:
@@ -71,7 +74,24 @@ namespace upm {
      */
     bool magnetDetected();
 
+    /**
+     * Install an Interrupt Service Routine (ISR) to be called when
+     * the appropriate magnetic field is detected.
+     *
+     * @param fptr function pointer to function to be called on interrupt
+     * @param arg pointer to an object that will be supplied as an
+     * arguement to the ISR.
+     */
+    void installISR(void (*isr)(void *), void *arg);
+
+    /**
+     * Uninstall the previously installed Interrupt Service Routine (ISR)
+     *
+     */
+    void uninstallISR();
+
   private:
+    bool m_isrInstalled;
     mraa_gpio_context m_gpio;
   };
 }