revise MRAA's GPIO implementation (#966)

resolves #965

RF24.cpp

@@ -1030,11 +1030,6 @@ bool RF24::_init_pins()
 
 #if defined(RF24_LINUX)
 
-    #if defined(MRAA)
-    GPIO();
-    gpio.begin(ce_pin, csn_pin);
-    #endif
-
     pinMode(ce_pin, OUTPUT);
     ce(LOW);
     delay(100);

RF24.h

@@ -127,9 +127,6 @@ class RF24
 #if defined(RF24_SPI_PTR)
     _SPI* _spi;
 #endif // defined (RF24_SPI_PTR)
-#if defined(MRAA)
-    GPIO gpio;
-#endif
 
     rf24_gpio_pin_t ce_pin;  /* "Chip Enable" pin, activates the RX or TX role */
     rf24_gpio_pin_t csn_pin; /* SPI Chip select */

utility/MRAA/RF24_arch_config.h

@@ -22,8 +22,6 @@
 
 #define RF24_LINUX
 //typedef uint16_t prog_uint16_t;
-typedef uint16_t rf24_gpio_pin_t;
-#define RF24_PIN_INVALID 0xFFFF
 
 #define PSTR(x)   (x)
 #define printf_P  printf
@@ -38,9 +36,9 @@ typedef uint16_t rf24_gpio_pin_t;
     #define IF_SERIAL_DEBUG(x)
 #endif
 
-#define digitalWrite(pin, value) gpio.write(pin, value)
+#define digitalWrite(pin, value) GPIO::write(pin, value)
 #define digitalRead(pin)         GPIO::read(pin)
-#define pinMode(pin, direction)  gpio.open(pin, direction)
+#define pinMode(pin, direction)  GPIO::open(pin, direction)
 
 #ifndef __TIME_H__
     // Prophet: Redefine time functions only if precompiled arduino time is not included

utility/MRAA/gpio.cpp

@@ -3,92 +3,74 @@
  *
  */
 
+#include <map>
 #include "gpio.h"
 
+// cache for mraa::Gpio instances
+std::map<rf24_gpio_pin_t, mraa::Gpio*> gpio_cache;
+
 GPIO::GPIO()
 {
-    // Prophet: basic members initialization
-    gpio_ce_pin = -1;
-    //gpio_cs_pin = -1;
-    gpio_0 = NULL;
-    //gpio_1 = NULL;
 }
 
 GPIO::~GPIO()
 {
-    // Prophet: this should free memory, and unexport pins when RF24 and/or GPIO gets deleted or goes out of scope
-    this->close(gpio_ce_pin);
-    //this->close(gpio_cs_pin);
-}
-
-void GPIO::begin(uint8_t ce_pin, uint8_t cs_pin)
-{
-    gpio_ce_pin = ce_pin;
-    //gpio_cs_pin = cs_pin;
-
-    // Prophet: owner can be set here, because we use our pins exclusively, and are making mraa:Gpio context persistent
-    // so pins will be unexported only if close is called, or on destruction
-    gpio_0 = new mraa::Gpio(ce_pin /*,0*/);
-    //gpio_1 = new mraa::Gpio(cs_pin/*,0*/);
+    // deinitialize cache of mraa::Gpio instances/pointers
+    std::map<rf24_gpio_pin_t, mraa::Gpio*>::iterator i;
+    for (i = gpio_cache.begin(); i != gpio_cache.end(); i++) {
+        i->second->close();
+    }
+    gpio_cache.clear();
 }
 
-void GPIO::open(int port, int DDR)
+void GPIO::open(rf24_gpio_pin_t port, mraa::Dir DDR)
 {
-    if (port == gpio_ce_pin) {
-        gpio_0 = new mraa::Gpio(port, 0);
-        // WARNING: use of memory mapped file system is deprecated in MRAA lib
-        gpio_0->useMmap(true); // `false` (or just not calling `useMmap()`) uses default file system?
-        gpio_0->dir((mraa::Dir)DDR);
+    // 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);
+    }
+    else {
+        i->second->dir(DDR);
     }
-    /*
-    else if(port == gpio_cs_pin) {
-        gpio_1 = new mraa::Gpio(port,0);
-        gpio_1->useMmap(true);
-        gpio_1->dir( (mraa::Dir)DDR);
-    }*/
 }
 
-void GPIO::close(int port)
+void GPIO::close(rf24_gpio_pin_t port)
 {
-    // Prophet: using same theme of working with port numbers as with GPIO::open,
-    // checking for mraa::Gpio context existence to be sure, that GPIO::begin was called
-    if (port == gpio_ce_pin) {
-        if (gpio_0 != NULL) {
-            delete gpio_0;
-        }
+    // check that mraa::Gpio context exists, meaning GPIO::open() was called.
+    std::map<rf24_gpio_pin_t, mraa::Gpio*>::iterator i = gpio_cache.find(port);
+    if (i != gpio_cache.end()) {
+        i->second->close();  // close the cached Gpio instance
+        gpio_cache.erase(i); // Delete cache entry
     }
-
-    /*
-    if(port == gpio_cs_pin) {
-        if (gpio_1 != NULL)	{
-            delete gpio_1;
-        }
-    }
-    */
 }
 
-int GPIO::read(int port)
+int GPIO::read(rf24_gpio_pin_t port)
 {
-    if (port == gpio_ce_pin) {
-        return gpio_0->read();
-    }
-    /*
-    else if(port == gpio_cs_pin) {
-        return gpio_1->read();
+    // get cache gpio instance
+    std::map<rf24_gpio_pin_t, mraa::Gpio*>::iterator i = gpio_cache.find(port);
+    if (i != gpio_cache.end()) {
+        return i->second->read();
     }
-    */
+    throw GPIOException("[GPIO::read] pin was not initialized with GPIO::open()");
     return -1;
 }
 
-void GPIO::write(int port, int value)
+void GPIO::write(rf24_gpio_pin_t port, int value)
 {
-
-    if (port == gpio_ce_pin) {
-        gpio_0->write(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);
+    }
+    else {
+        throw GPIOException("[GPIO::write] pin was not initialized with GPIO::open()");
     }
-    /*
-    else if(port == gpio_cs_pin) {
-        gpio_1->write( value);
+
+    if (result != mraa::Result::SUCCESS) {
+        throw GPIOException("GPIO::write() failed");
     }
-    */
 }

utility/MRAA/gpio.h

@@ -6,8 +6,22 @@
 #ifndef RF24_UTILITY_MRAA_GPIO_H_
 #define RF24_UTILITY_MRAA_GPIO_H_
 
+#include <stdexcept> // std::runtime_error, std::string
 #include "mraa.hpp"
 
+typedef uint16_t rf24_gpio_pin_t;
+#define RF24_PIN_INVALID 0xFFFF
+
+/** Specific exception for GPIO errors */
+class GPIOException : public std::runtime_error
+{
+public:
+    explicit GPIOException(const std::string& msg)
+        : std::runtime_error(msg)
+    {
+    }
+};
+
 class GPIO
 {
 
@@ -16,21 +30,13 @@ class GPIO
 
     virtual ~GPIO();
 
-    void begin(uint8_t ce_pin, uint8_t cs_pin);
-
-    void open(int port, int DDR);
-
-    void close(int port);
+    static void open(rf24_gpio_pin_t port, mraa::Dir DDR);
 
-    int read(int port);
+    static void close(rf24_gpio_pin_t port);
 
-    void write(int port, int value);
+    static int read(rf24_gpio_pin_t port);
 
-private:
-    int gpio_ce_pin; /** ce_pin value of the RF24 device **/
-    // int gpio_cs_pin;    /** cs_pin value of the RF24 device **/
-    mraa::Gpio* gpio_0; /** gpio object for ce_pin **/
-    // mraa::Gpio* gpio_1; /** gpio object for cs_pin **/
+    static void write(rf24_gpio_pin_t port, int value);
 };
 
 #endif // RF24_UTILITY_MRAA_GPIO_H_