Mutex handling for interrupts on RPi

- Create separate mutex for SPI vs User data handling
Problems:
A: Memory/Data conflicts became apparent after time without thread-safe
queues
B: Without implementing locking at the SPI level, even simple code
examples (rx_transfer.cpp) would hang if a write was done out of sync
with reads

Solutions:
A: Keep initial locking mechanism for users
B: Implement separate automatic mutex and locking mechanism for SPI

#172 #173

utility/RPi/interrupt.c

@@ -24,6 +24,7 @@ see <http://www.gnu.org/licenses/>
 #define delay(x) bcm2835_delay(x)
 
 static pthread_mutex_t pinMutex ;
+static pthread_mutex_t spiMutex ;
 static volatile int    pinPass = -1 ;
 // sysFds:
 //      Map a file descriptor from the /sys/class/gpio/gpioX/value
@@ -92,8 +93,11 @@ void *interruptHandler (void *arg)
   pinPass = -1 ;
 
   for (;;)
-    if (waitForInterrupt (myPin, -1) > 0)
+    if (waitForInterrupt (myPin, -1) > 0){
+      pthread_mutex_lock (&pinMutex) ;
       isrFunctions [myPin] () ;
+      pthread_mutex_unlock (&pinMutex) ;
+    }
 
   return NULL ;
 }
@@ -176,3 +180,12 @@ void rfInterrupts(){
   pthread_mutex_unlock (&pinMutex) ;
 }
 
+void spiNoInterrupts(){
+  pthread_mutex_lock (&spiMutex) ;
+}
+
+void spiInterrupts(){
+  pthread_mutex_unlock (&spiMutex) ;
+}
+
+

utility/RPi/interrupt.h

@@ -54,6 +54,8 @@ extern int piHiPri (const int pri);
 extern int attachInterrupt (int pin, int mode, void (*function)(void));
 extern void rfNoInterrupts();
 extern void rfInterrupts();
+extern void spiNoInterrupts();
+extern void spiInterrupts();
 #ifdef __cplusplus
 }
 #endif
\ No newline at end of file

utility/RPi/spi.cpp

@@ -8,14 +8,13 @@ SPI::SPI() {
 
 
 void SPI::begin( int busNo ) {
-	rfNoInterrupts();
+    spiNoInterrupts();
 	if (!bcm2835_init()){
 		return;
 	}
 	
 	bcm2835_spi_begin();
-    rfInterrupts();
-	
+	spiInterrupts();
 }
 
 void SPI::end() {
@@ -23,27 +22,27 @@ void SPI::end() {
 }
 
 void SPI::setBitOrder(uint8_t bit_order) {
-    rfNoInterrupts();
+    spiNoInterrupts();
 	bcm2835_spi_setBitOrder(bit_order);
-    rfInterrupts();
+    spiInterrupts();
 }
 
 void SPI::setDataMode(uint8_t data_mode) {
-  rfNoInterrupts();
+  spiNoInterrupts();
   bcm2835_spi_setDataMode(data_mode);
-  rfInterrupts();
+  spiInterrupts();
 }
 
 void SPI::setClockDivider(uint16_t spi_speed) {
-    rfNoInterrupts();
+    spiNoInterrupts();
 	bcm2835_spi_setClockDivider(spi_speed);
-    rfInterrupts();
+    spiInterrupts();
 }
 
 void SPI::chipSelect(int csn_pin){
-    rfNoInterrupts();
+    spiNoInterrupts();
 	bcm2835_spi_chipSelect(csn_pin);
-    rfInterrupts();
+    spiInterrupts();
 }
 
 SPI::~SPI() {

utility/RPi/spi.h

@@ -14,6 +14,7 @@
 #include "bcm2835.h"
 #include "interrupt.h"
 
+
 class SPI {
 public:
 
@@ -35,23 +36,23 @@ public:
 
 
 uint8_t SPI::transfer(uint8_t _data) {
-    rfNoInterrupts();
+    spiNoInterrupts();
     uint8_t data = bcm2835_spi_transfer(_data);	
-    rfInterrupts();
+    spiInterrupts();
     return data;
 }
 
 void SPI::transfernb(char* tbuf, char* rbuf, uint32_t len){
-   rfNoInterrupts();
+   spiNoInterrupts();
    bcm2835_spi_transfernb( tbuf, rbuf, len);
-   rfInterrupts();
+   spiInterrupts();
 }
 
 void SPI::transfern(char* buf, uint32_t len)
 {
-    rfNoInterrupts();
+    spiNoInterrupts();
     transfernb(buf, buf, len);
-    rfInterrupts();
+    spiInterrupts();
 }
 /**
  * \endcond