wrap MRAA lib's Gpio::isr() for IRQ support (#970)

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

* update example's IRQ_PIN value
* don't arbitrarily link example binaries to pigpio
* improve MRAA exception messages

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 
     ${RF24}
@@ -52,10 +46,14 @@ elseif("${RF24_DRIVER}" STREQUAL "wiringPi")
     else()
         message(FATAL "Lib ${RF24_DRIVER} not found.")
     endif()
-elseif(NOT "${LibPIGPIO}" STREQUAL "LibPIGPIO-NOTFOUND")
-    message(STATUS "linking to ${LibPIGPIO}")
-    # linking to pigpio requires pthread to be listed as last linked lib
-    list(APPEND linked_libs ${LibPIGPIO} pthread)
+elseif("${RF24_DRIVER}" STREQUAL "pigpio")
+    if(NOT "${LibPIGPIO}" STREQUAL "LibPIGPIO-NOTFOUND")
+        message(STATUS "linking to ${LibPIGPIO}")
+        # linking to pigpio requires pthread to be listed as last linked lib
+        list(APPEND linked_libs ${LibPIGPIO} pthread)
+    else()
+        message(FATAL "Lib ${RF24_DRIVER} not found")
+    endif()
 endif()
 
 foreach(example ${EXAMPLES_LIST})

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

examples_linux/interruptConfigure.cpp

@@ -22,7 +22,13 @@
 using namespace std;
 
 // We will be using the nRF24L01's IRQ pin for this example
-#define IRQ_PIN 24 // this needs to be a digital input capable pin
+#ifdef MRAA
+    #define IRQ_PIN 18 // GPIO24
+#elif defined(RF24_WIRINGPI)
+    #define IRQ_PIN 5 // GPIO24
+#else
+    #define IRQ_PIN 24 // GPIO24
+#endif
 
 // this example is a sequential program. so we need to wait for the event to be handled
 volatile bool got_interrupt = false; // used to signify that the event started

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/gpio.cpp

@@ -4,6 +4,7 @@
  */
 
 #include <map>
+#include <mraa.h> // mraa_strresult()
 #include "gpio.h"
 
 // cache for mraa::Gpio instances
@@ -25,15 +26,22 @@ GPIO::~GPIO()
 
 void GPIO::open(rf24_gpio_pin_t port, mraa::Dir DDR)
 {
+    mraa::Result status;
+
     // check that mraa::Gpio context doesn't already exist
     std::map<rf24_gpio_pin_t, mraa::Gpio*>::iterator i = gpio_cache.find(port);
     if (i == gpio_cache.end()) {
         mraa::Gpio* gpio_inst = new mraa::Gpio(port);
         gpio_cache[port] = gpio_inst;
-        gpio_inst->dir(DDR);
+        status = gpio_inst->dir(DDR);
     }
     else {
-        i->second->dir(DDR);
+        status = i->second->dir(DDR);
+    }
+    if (status != mraa::SUCCESS) {
+        std::string msg = "[GPIO::open] Could not set the pin direction; ";
+        msg += mraa_strresult((mraa_result_t)status);
+        throw GPIOException(msg);
     }
 }
 
@@ -60,17 +68,17 @@ int GPIO::read(rf24_gpio_pin_t port)
 
 void GPIO::write(rf24_gpio_pin_t port, int value)
 {
-    mraa::Result result = mraa::Result::ERROR_UNSPECIFIED; // a default
     // get cache gpio instance
     std::map<rf24_gpio_pin_t, mraa::Gpio*>::iterator i = gpio_cache.find(port);
     if (i != gpio_cache.end()) {
-        result = i->second->write(value);
+        mraa::Result result = i->second->write(value);
+        if (result != mraa::Result::SUCCESS) {
+            std::string msg = "[GPIO::write] Could not set pin output value; ";
+            msg += mraa_strresult((mraa_result_t)result);
+            throw GPIOException(msg);
+        }
     }
     else {
         throw GPIOException("[GPIO::write] pin was not initialized with GPIO::open()");
     }
-
-    if (result != mraa::Result::SUCCESS) {
-        throw GPIOException("GPIO::write() failed");
-    }
 }

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_

utility/MRAA/spi.cpp

@@ -1,6 +1,6 @@
 
+#include <mraa.h> // mraa_strresult(), mraa_result_t
 #include "spi.h"
-#include "mraa.h"
 
 SPI::SPI()
 {
@@ -12,11 +12,32 @@ void SPI::begin(int busNo, uint32_t spi_speed)
     // init mraa spi bus, it will handle chip select internally. For CS pin wiring user must check SPI details in hardware manual
     mspi = new mraa::Spi(busNo);
 
-    mspi->mode(mraa::SPI_MODE0);
-    mspi->bitPerWord(8);
+    mraa::Result result;
+
+    result = mspi->mode(mraa::SPI_MODE0);
+    if (result != mraa::Result::SUCCESS) {
+        std::string msg = "[SPI::begin] Could not set bus mode;";
+        msg += mraa_strresult((mraa_result_t)result);
+        throw SPIException(msg);
+        return;
+    }
+
+    result = mspi->bitPerWord(8);
+    if (result != mraa::Result::SUCCESS) {
+        std::string msg = "[SPI::begin] Could not set bus bits per word;";
+        msg += mraa_strresult((mraa_result_t)result);
+        throw SPIException(msg);
+        return;
+    }
 
     // Prophet: this will try to set 8MHz, however MRAA will reset to max platform speed and syslog a message of it
-    mspi->frequency(spi_speed);
+    result = mspi->frequency(spi_speed);
+    if (result != mraa::Result::SUCCESS) {
+        std::string msg = "[SPI::begin] Could not set bus frequency;";
+        msg += mraa_strresult((mraa_result_t)result);
+        throw SPIException(msg);
+        return;
+    }
 }
 
 void SPI::end()

utility/MRAA/spi.h

@@ -10,10 +10,23 @@
  * Class declaration for SPI helper files
  */
 
-#include "mraa.h"
-#include "mraa.hpp"
+#include <stdexcept> // std::exception, std::string
+#include <mraa.hpp>  // mraa::
 
-#include "../../RF24_config.h" // This is cyclical and should be fixed
+/** @brief The default SPI speed (in Hz) */
+#ifndef RF24_SPI_SPEED
+    #define RF24_SPI_SPEED 10000000
+#endif
+
+/** Specific exception for SPI errors */
+class SPIException : public std::runtime_error
+{
+public:
+    explicit SPIException(const std::string& msg)
+        : std::runtime_error(msg)
+    {
+    }
+};
 
 class SPI
 {
@@ -34,12 +47,16 @@ class SPI
 
     void end();
 
+    // not actually used in Linux
     void setBitOrder(uint8_t bit_order);
 
+    // not actually used in Linux
     void setDataMode(uint8_t data_mode);
 
+    // not actually used in Linux
     void setClockDivider(uint32_t spi_speed);
 
+    // not actually used in Linux
     void chipSelect(int csn_pin);
 };