improve MRAA exception messages

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/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);
 };