Add mutex locking to SPI functions for RPi

per #172 #173

- Add mutex locking to SPI for RPi interrupt usage
- Leave rfInterrupts() rfNoInterrupts() functions for testing purposes

utility/RPi/interrupt.c

@@ -168,3 +168,11 @@ int attachInterrupt (int pin, int mode, void (*function)(void))
   return 0 ;
 }
 
+void rfNoInterrupts(){
+  pthread_mutex_lock (&pinMutex) ;
+}
+
+void rfInterrupts(){
+  pthread_mutex_unlock (&pinMutex) ;
+}
+

utility/RPi/interrupt.h

@@ -52,6 +52,8 @@ extern int piHiPri (const int pri);
  *********************************************************************************
  */
 extern int attachInterrupt (int pin, int mode, void (*function)(void));
+extern void rfNoInterrupts();
+extern void rfInterrupts();
 #ifdef __cplusplus
 }
 #endif
\ No newline at end of file

utility/RPi/spi.cpp

@@ -8,12 +8,13 @@ SPI::SPI() {
 
 
 void SPI::begin( int busNo ) {
-	
+	rfNoInterrupts();
 	if (!bcm2835_init()){
 		return;
 	}
 	
 	bcm2835_spi_begin();
+    rfInterrupts();
 	
 }
 
@@ -22,19 +23,27 @@ void SPI::end() {
 }
 
 void SPI::setBitOrder(uint8_t bit_order) {
+    rfNoInterrupts();
 	bcm2835_spi_setBitOrder(bit_order);
+    rfInterrupts();
 }
 
 void SPI::setDataMode(uint8_t data_mode) {
+  rfNoInterrupts();
   bcm2835_spi_setDataMode(data_mode);
+  rfInterrupts();
 }
 
 void SPI::setClockDivider(uint16_t spi_speed) {
+    rfNoInterrupts();
 	bcm2835_spi_setClockDivider(spi_speed);
+    rfInterrupts();
 }
 
 void SPI::chipSelect(int csn_pin){
+    rfNoInterrupts();
 	bcm2835_spi_chipSelect(csn_pin);
+    rfInterrupts();
 }
 
 SPI::~SPI() {

utility/RPi/spi.h

@@ -12,6 +12,7 @@
 
 #include <stdio.h>
 #include "bcm2835.h"
+#include "interrupt.h"
 
 class SPI {
 public:
@@ -34,16 +35,23 @@ public:
 
 
 uint8_t SPI::transfer(uint8_t _data) {
-	return bcm2835_spi_transfer(_data);
+    rfNoInterrupts();
+    uint8_t data = bcm2835_spi_transfer(_data);	
+    rfInterrupts();
+    return data;
 }
 
 void SPI::transfernb(char* tbuf, char* rbuf, uint32_t len){
+   rfNoInterrupts();
    bcm2835_spi_transfernb( tbuf, rbuf, len);
+   rfInterrupts();
 }
 
 void SPI::transfern(char* buf, uint32_t len)
 {
+    rfNoInterrupts();
     transfernb(buf, buf, len);
+    rfInterrupts();
 }
 /**
  * \endcond