Due & RPi bugfix - #9 - root cause resolved

- Discovered a bug affecting Arduino Due using extended SPI methods, it
seems an extra delay is required before switching to TX mode
- Found the same bug affected the RPi, and removed all delays from
bcm2835 driver, since this bug caused the strange behaviour on RPi

RF24.cpp

@@ -205,10 +205,8 @@ uint8_t RF24::read_payload(void* buf, uint8_t data_len)
 
 	while ( --blank_len ){
 	  SPI.transfer(csn_pin,0xFF, SPI_CONTINUE);
-	  delayMicroseconds(10);
 	}
 	SPI.transfer(csn_pin,0xFF);
-	delayMicroseconds(10);
   }else{
 	while ( --data_len ){
 	  *current++ = SPI.transfer(csn_pin,0xFF, SPI_CONTINUE);
@@ -531,9 +529,14 @@ void RF24::startListening(void)
 
 void RF24::stopListening(void)
 {
+
   ce(LOW);
+  #if defined(__arm__)
+  	delayMicroseconds(130);
+  #endif
   flush_tx();
   flush_rx();
+
   write_register(CONFIG, ( read_register(CONFIG) ) & ~_BV(PRIM_RX) );
   delayMicroseconds(130); //Found that adding this delay back actually increases response time
 }

RPi/RF24/RF24.cpp

@@ -54,7 +54,7 @@ uint8_t RF24::read_register(uint8_t reg)
 	*ptx++ = ( R_REGISTER | ( REGISTER_MASK & reg ) );
 	*ptx++ = NOP ; // Dummy operation, just for reading
 
-  bcm2835_spi_transfernbd( (char *) spi_txbuff, (char *) spi_rxbuff, 2);
+  bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, 2);
 
 	result = *++prx;   // result is 2nd byte of receive buffer
 
@@ -73,7 +73,7 @@ uint8_t RF24::write_register(uint8_t reg, uint8_t value)
 	*ptx++ = ( W_REGISTER | ( REGISTER_MASK & reg ) );
 	*ptx = value ;
 
-  	bcm2835_spi_transfernbd( (char *) spi_txbuff, (char *) spi_rxbuff, 2);  
+  	bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, 2);  
 
 	status = *prx++; // status is 1st byte of receive buffer
 
@@ -129,7 +129,6 @@ uint8_t RF24::write_payload(const void* buf, uint8_t len, const uint8_t writeTyp
   while ( blank_len-- )
 		*ptx++ =  0;
 
-
 	bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, size);
 
 	status = *prx; // status is 1st byte of receive buffer
@@ -164,11 +163,8 @@ uint8_t RF24::read_payload(void* buf, uint8_t len)
 	// Size has been lost during while, re affect
 	size = data_len + blank_len + 1; // Add register value to transmit buffer
 
-	if(dynamic_payloads_enabled){
-		bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, size);
-	}else{
-		bcm2835_spi_transfernbd( (char *) spi_txbuff, (char *) spi_rxbuff, size);
-	}
+	bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, size);
+
 	// 1st byte is status
 	status = *prx++;
 
@@ -534,8 +530,9 @@ void RF24::stopListening(void)
   bcm2835_gpio_write(ce_pin, LOW);
   flush_tx();
   flush_rx();
+  delayMicroseconds(150);
   write_register(CONFIG, ( read_register(CONFIG) ) & ~_BV(PRIM_RX) );  
-  delayMicroseconds(130);
+  delayMicroseconds(150);
 }
 
 /****************************************************************************/
@@ -736,7 +733,7 @@ uint8_t RF24::getDynamicPayloadSize(void)
   spi_txbuff[0] = R_RX_PL_WID;
   spi_rxbuff[1] = 0xff;
 
-  bcm2835_spi_transfernbd( (char *) spi_txbuff, (char *) spi_rxbuff, 2);
+  bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, 2);
 
   if(spi_rxbuff[1] > 32) { flush_rx(); return 0; }
 

RPi/RF24/bcm2835.c

@@ -584,19 +584,9 @@ uint8_t bcm2835_spi_transfer(uint8_t value)
     return ret;
 }
 
-void bcm2835_spi_transfernb(char* tbuf, char* rbuf, uint32_t len)
-{
-	__bcm2835_spi_transfernb(tbuf,rbuf,len,0);
-}
-
-void bcm2835_spi_transfernbd(char* tbuf, char* rbuf, uint32_t len)
-{
-	__bcm2835_spi_transfernb(tbuf,rbuf,len,1);
-}
-
 
 // Writes (and reads) an number of bytes to SPI
-void __bcm2835_spi_transfernb(char* tbuf, char* rbuf, uint32_t len, uint8_t delay)
+void bcm2835_spi_transfernb(char* tbuf, char* rbuf, uint32_t len)
 {
     volatile uint32_t* paddr = bcm2835_spi0 + BCM2835_SPI0_CS/4;
     volatile uint32_t* fifo = bcm2835_spi0 + BCM2835_SPI0_FIFO/4;
@@ -623,15 +613,14 @@ void __bcm2835_spi_transfernb(char* tbuf, char* rbuf, uint32_t len, uint8_t dela
            TXCnt++;
 		   
         }	
-        //Rx fifo not empty, so get the next received bytes
-	while(! (bcm2835_peri_read(paddr) & BCM2835_SPI0_CS_DONE) ){}
-	if(TXCnt == len){ bcm2835_peri_set_bits(paddr, 0, BCM2835_SPI0_CS_TA); if(delay){ delayMicroseconds(20);}}	
+        //Rx fifo not empty, so get the next received bytes		
         while(((bcm2835_peri_read(paddr) & BCM2835_SPI0_CS_RXD))&&( RXCnt < len )){		   
            rbuf[RXCnt] = bcm2835_peri_read_nb(fifo);
            RXCnt++;	   
         }
     }
-	delayMicroseconds(5);
+	while(! (bcm2835_peri_read(paddr) & BCM2835_SPI0_CS_DONE) ){}
+	if(TXCnt == len){ bcm2835_peri_set_bits(paddr, 0, BCM2835_SPI0_CS_TA);}
 }
 
 

RPi/RF24/bcm2835.h

@@ -1177,8 +1177,6 @@ extern "C" {
     /// \param[in] len Number of bytes in the tbuf buffer, and the number of bytes to send/received
     /// \sa bcm2835_spi_transfer()
     extern void bcm2835_spi_transfernb(char* tbuf, char* rbuf, uint32_t len);
-    extern void bcm2835_spi_transfernbd(char* tbuf, char* rbuf, uint32_t len);
-    extern void __bcm2835_spi_transfernb(char* tbuf, char* rbuf, uint32_t len,uint8_t delay);
 
     /// Transfers any number of bytes to and from the currently selected SPI slave
     /// using bcm2835_spi_transfernb.