Minor chgs to mirror Arduino SPI transaction API

- Bring beginTransaction inline with Arduino API
- #define SPI_HAS_TRANSACTION in SPI.h
- #define the spi speed on both Arduino and RPi/Linux using
RF24_SPI_SPEED instead of different vars
- Chg beginTransaction to use bitOrder & mode instead of CSN
- Add delay directly to chipSelect function (helps ensure pin is active
before beginning SPI transactions)

#173

RF24.cpp

@@ -43,6 +43,9 @@ void RF24::csn(bool mode)
 		_SPI.setDataMode(SPI_MODE0);
 		_SPI.setClockDivider(SPI_CLOCK_DIV2);
       #endif
+#elif defined (RF24_RPi)
+      if(!mode)
+	    _SPI.chipSelect(csn_pin);
 #endif
 
 #if !defined (RF24_LINUX)
@@ -66,9 +69,6 @@ void RF24::ce(bool level)
     #if defined (RF24_SPI_TRANSACTIONS)
     _SPI.beginTransaction(SPISettings(RF_SPI_SPEED, MSBFIRST, SPI_MODE0));
 	#endif
-	#if defined (RF24_LINUX)
-	_SPI.beginTransaction(spi_speed ? spi_speed : RF24_CLOCK_DIVIDER, csn_pin);
-	#endif
     csn(LOW);
   }
 
@@ -79,9 +79,6 @@ void RF24::ce(bool level)
 	#if defined (RF24_SPI_TRANSACTIONS)
     _SPI.endTransaction();
 	#endif
-	#if defined (RF24_LINUX)
-	_SPI.endTransaction();
-	#endif
   }
 
 /****************************************************************************/

RF24.h

@@ -68,8 +68,8 @@ private:
 
   uint8_t ce_pin; /**< "Chip Enable" pin, activates the RX or TX role */
   uint8_t csn_pin; /**< SPI Chip select */
-#if defined (RF24_LINUX)
   uint16_t spi_speed; /**< SPI Bus Speed */
+#if defined (RF24_LINUX)
   uint8_t spi_rxbuff[32+1] ; //SPI receive buffer (payload max 32 bytes)
   uint8_t spi_txbuff[32+1] ; //SPI transmit buffer (payload max 32 bytes + 1 byte for the command)
 #endif  

RF24_config.h

@@ -58,7 +58,7 @@
   #include <Arduino.h>
   
   // RF modules support 10 Mhz SPI bus speed
-  const uint32_t RF_SPI_SPEED = 10000000;  
+  const uint32_t RF24_SPI_SPEED = 10000000;  
 
 #if defined (ARDUINO) && !defined (__arm__) && !defined (__ARDUINO_X86__)
       #if defined SPI_UART

utility/RPi/RF24_arch_config.h

@@ -16,7 +16,7 @@
   #define _SPI spi
     #define RF24_BIT_ORDER BCM2835_SPI_BIT_ORDER_MSBFIRST
 	#define RF24_DATA_MODE BCM2835_SPI_MODE0
-	#define RF24_CLOCK_DIVIDER BCM2835_SPI_SPEED_8MHZ
+	#define RF24_SPI_SPEED BCM2835_SPI_SPEED_8MHZ
 		
   // GCC a Arduino Missing
   #define _BV(x) (1<<(x))

utility/RPi/spi.cpp

@@ -16,13 +16,12 @@ void SPI::begin( int busNo ) {
 	bcm2835_spi_begin();
 }
 
-void SPI::beginTransaction(int clock_divider, uint8_t csn_pin) {
+void SPI::beginTransaction(int clock_divider, uint8_t bitOrder, uint8_t mode) {
+   
 	pthread_mutex_lock (&spiMutex);
-	setBitOrder(RF24_BIT_ORDER);
-	setDataMode(RF24_DATA_MODE);
+	setBitOrder(bitOrder);
+	setDataMode(mode);
 	setClockDivider(clock_divider);
-	chipSelect(csn_pin);
-	delayMicroseconds(5);
 }
 
 void SPI::endTransaction() {
@@ -43,6 +42,7 @@ void SPI::setClockDivider(uint16_t spi_speed) {
 
 void SPI::chipSelect(int csn_pin){
 	bcm2835_spi_chipSelect(csn_pin);
+	delayMicroseconds(5);
 }
 
 SPI::~SPI() {

utility/RPi/spi.h

@@ -14,6 +14,7 @@
 #include "bcm2835.h"
 #include "interrupt.h"
 
+#define SPI_HAS_TRANSACTION
 
 class SPI {
 public:
@@ -33,7 +34,7 @@ public:
   static void setClockDivider(uint16_t spi_speed);
   static void chipSelect(int csn_pin);
   
-  static void beginTransaction(int clock_divider, uint8_t csn_pin);
+  static void beginTransaction(int clock_divider, uint8_t bitOrder, uint8_t mode);
   static void endTransaction();
 };