wrap MRAA lib's Gpio::isr() for IRQ support

I also removed MRAA exclusion from examples build. Previously, interruptConfigure.cpp was not built for MRAA driver.

Makefile

@@ -19,7 +19,7 @@ include $(CONFIG_FILE)
 # Objects to compile
 OBJECTS=RF24.o
 ifeq ($(DRIVER), MRAA)
-OBJECTS+=spi.o gpio.o compatibility.o
+OBJECTS+=spi.o gpio.o compatibility.o interrupt.o
 else ifeq ($(DRIVER), RPi)
 OBJECTS+=spi.o bcm2835.o compatibility.o interrupt.o
 else ifeq ($(DRIVER), SPIDEV)

examples_linux/CMakeLists.txt

@@ -8,6 +8,7 @@ set(EXAMPLES_LIST
     streamingData
     multiceiverDemo
     scanner
+    interruptConfigure
 )
 
 project(RF24Examples CXX)
@@ -23,13 +24,6 @@ include(../cmake/AutoConfig_RF24_DRIVER.cmake)
 find_library(RF24 rf24 REQUIRED)
 message(STATUS "using RF24 library: ${RF24}")
 
-# conditionally append "interruptConfigure" to the EXAMPLES_LIST
-if("${RF24_DRIVER}" STREQUAL "MRAA")
-    message(STATUS "Skipping interruptConfigure.cpp example as it is incompatible with selected driver library")
-else() # not using MRAA or wiringPi drivers (or pigpio lib was found)
-    list(APPEND EXAMPLES_LIST interruptConfigure)
-endif()
-
 
 set(linked_libs 
     ${RF24}

examples_linux/Makefile

@@ -18,9 +18,6 @@ endif
 include ../Makefile.inc
 
 # define all programs
-PROGRAMS = gettingstarted acknowledgementPayloads manualAcknowledgements streamingData multiceiverDemo scanner
-ifneq ($(DRIVER), MRAA)
-PROGRAMS+=interruptConfigure
-endif
+PROGRAMS = gettingstarted acknowledgementPayloads manualAcknowledgements streamingData multiceiverDemo scanner interruptConfigure
 
 include Makefile.examples

utility/CMakeLists.txt

@@ -67,6 +67,7 @@ elseif("${RF24_DRIVER}" STREQUAL "MRAA") # use MRAA
         ${CMAKE_CURRENT_LIST_DIR}/${RF24_DRIVER}/spi.cpp
         ${CMAKE_CURRENT_LIST_DIR}/${RF24_DRIVER}/compatibility.cpp
         ${CMAKE_CURRENT_LIST_DIR}/${RF24_DRIVER}/RF24_arch_config.h
+        ${CMAKE_CURRENT_LIST_DIR}/${RF24_DRIVER}/interrupt.cpp
         PARENT_SCOPE
     )
     install(FILES
@@ -75,7 +76,8 @@ elseif("${RF24_DRIVER}" STREQUAL "MRAA") # use MRAA
             ${RF24_DRIVER}/spi.h
             ${RF24_DRIVER}/compatibility.h
             ${RF24_DRIVER}/RF24_arch_config.h
-        DESTINATION include/RF24/utility/${RF24_DRIVER}
+            ${CMAKE_CURRENT_LIST_DIR}/${RF24_DRIVER}/interrupt.h
+            DESTINATION include/RF24/utility/${RF24_DRIVER}
     )
 elseif("${RF24_DRIVER}" STREQUAL "pigpio") # use pigpio
     set(RF24_LINKED_DRIVER ${LibPIGPIO} PARENT_SCOPE)

utility/MRAA/includes.h

@@ -6,5 +6,6 @@
 #endif
 
 #include "MRAA/RF24_arch_config.h"
+#include "MRAA/interrupt.h"
 
 #endif // RF24_UTILITY_INCLUDES_H_

utility/MRAA/interrupt.cpp

@@ -0,0 +1,58 @@
+#include <map>
+#include <mraa.h>   // mraa_strresult()
+#include <mraa.hpp> // mraa::Gpio
+#include "interrupt.h"
+#include "gpio.h" // rf24_gpio_pin_t
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+std::map<rf24_gpio_pin_t, mraa::Gpio*> irqCache;
+
+int attachInterrupt(rf24_gpio_pin_t pin, uint8_t mode, void (*function)(void))
+{
+    // ensure pin is not already being used in a separate thread
+    detachInterrupt(pin);
+    GPIO::close(pin);
+
+    mraa::Gpio* gpio = new mraa::Gpio(pin);
+    mraa::Result status = gpio->dir(mraa::DIR_IN);
+    if (status != mraa::SUCCESS) {
+        std::string msg = "[attachInterrupt] Could not set the pin as an input; ";
+        msg += mraa_strresult((mraa_result_t)status);
+        throw IRQException(msg);
+        return 0;
+    }
+    status = gpio->isr((mraa::Edge)mode, (void (*)(void*))function, NULL);
+    if (status != mraa::SUCCESS) {
+        std::string msg = "[attachInterrupt] Could not setup the ISR; ";
+        msg += mraa_strresult((mraa_result_t)status);
+        throw IRQException(msg);
+        return 0;
+    }
+
+    std::pair<std::map<rf24_gpio_pin_t, mraa::Gpio*>::iterator, bool> indexPair = irqCache.insert(std::pair<rf24_gpio_pin_t, mraa::Gpio*>(pin, gpio));
+    if (!indexPair.second) {
+        // this should not be reached, but indexPair.first needs to be the inserted map element
+        gpio->close();
+        throw IRQException("[attachInterrupt] Could not cache the mraa::Gpio object");
+        return 0;
+    }
+    return 1;
+}
+
+int detachInterrupt(rf24_gpio_pin_t pin)
+{
+    std::map<rf24_gpio_pin_t, mraa::Gpio*>::iterator cachedPin = irqCache.find(pin);
+    if (cachedPin == irqCache.end()) {
+        return 0; // pin not in cache; just exit
+    }
+    cachedPin->second->close();
+    irqCache.erase(cachedPin);
+    return 1;
+}
+
+#ifdef __cplusplus
+}
+#endif

utility/MRAA/interrupt.h

@@ -0,0 +1,44 @@
+#ifndef RF24_UTILITY_MRAA_INTERRUPT_H_
+#define RF24_UTILITY_MRAA_INTERRUPT_H_
+
+#include <stdexcept> // std::exception, std::string
+#include "mraa.hpp"  // mraa::
+#include "gpio.h"    // rf24_gpio_pin_t
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum Edge
+{
+    INT_EDGE_FALLING = mraa::Edge::EDGE_FALLING,
+    INT_EDGE_RISING = mraa::Edge::EDGE_RISING,
+    INT_EDGE_BOTH = mraa::Edge::EDGE_BOTH,
+};
+
+/** Specific exception for IRQ errors */
+class IRQException : public std::runtime_error
+{
+public:
+    explicit IRQException(const std::string& msg)
+        : std::runtime_error(msg)
+    {
+    }
+};
+
+/**
+ * Take the details and create an interrupt handler that will
+ * callback to the user-supplied function.
+ */
+int attachInterrupt(rf24_gpio_pin_t pin, uint8_t mode, void (*function)(void));
+
+/**
+ * Will cancel the interrupt thread, close the filehandle and release the pin.
+ */
+int detachInterrupt(rf24_gpio_pin_t pin);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // RF24_UTILITY_MRAA_INTERRUPT_H_