Fix: Due write() issues.

Found that Due would send multiple payloads or fail in writing in some
cases. Change ensures single-payload transmission using write().
- Updated pingpair_dyn.ino example sketch to conform with available()
changes
- Slight doc update

RF24.cpp

@@ -579,15 +579,13 @@ void RF24::powerUp(void)
 bool RF24::write( const void* buf, uint8_t len )
 {
 	//Start Writing
-    startFastWrite(buf,len);
+    startWrite(buf,len);
 
 	//Wait until complete or failed
 	//ACK payloads that are handled improperly will cause this to hang
 	//If autoAck is ON, a payload has to be written prior to reading a payload, else write after reading a payload
 	while( ! ( get_status()  & ( _BV(TX_DS) | _BV(MAX_RT) ))) { }
 
-	ce(LOW); //Set the radio back to STANDBY-I mode since we can only fill one buffer at a time using this method, and tx is complete
-
 	uint8_t status = write_register(STATUS,_BV(RX_DR) | _BV(TX_DS) | _BV(MAX_RT) );
 
   //Max retries exceeded

RF24.h

@@ -263,6 +263,9 @@ public:
    * timeout, and return 1 or 0 respectively. From a user perspective, just
    * keep trying to send the same data. The library will keep auto retrying
    * the current payload using the built in functionality.
+   * @warning It is important to never keep the nRF24L01 in TX mode for more than 4ms at a time. If the auto
+   * retransmit is enabled, the nRF24L01 is never in TX mode long enough to disobey this rule. Allow the FIFO
+   * to clear by issuing txStandBy() or ensure appropriate time between transmissions.
    *
    * ONLY max retry interrupt flags will be cleared when writeFast is called
    *
@@ -292,6 +295,9 @@ public:
    * It will not block until the 3 FIFO buffers are filled with data.
    * If so the library will auto retry until a new payload is written
    * or the user specified timeout period is reached.
+   * @warning It is important to never keep the nRF24L01 in TX mode for more than 4ms at a time. If the auto
+   * retransmit is enabled, the nRF24L01 is never in TX mode long enough to disobey this rule. Allow the FIFO
+   * to clear by issuing txStandBy() or ensure appropriate time between transmissions.
    *
    * ONLY max retry interrupt flags will be cleared when writeBlocking is called
    * @code
@@ -409,6 +415,9 @@ public:
    * @note Optimization: This function now leaves the CE pin high, so the radio
    * will remain in TX or STANDBY-II Mode until a txStandBy() command is issued.
    * This allows the chip to be used to its full potential in TX mode.
+   * @warning It is important to never keep the nRF24L01 in TX mode for more than 4ms at a time. If the auto
+   * retransmit is enabled, the nRF24L01 is never in TX mode long enough to disobey this rule. Allow the FIFO
+   * to clear by issuing txStandBy() or ensure appropriate time between transmissions.
    *
    * @see write()
    * @see writeFast()
@@ -500,7 +509,20 @@ public:
   bool isValid() { return ce_pin != 0xff && csn_pin != 0xff; }
 
   /**
+  * The radio will generate interrupt signals when a transmission is complete,
+  * a transmission fails, or a payload is received. This allows users to mask
+  * those interrupts to prevent them from generating a signal on the interrupt
+  * pin.
   *
+  * @code
+  * 	Mask all interrupts except the receive interrupt:
+  *
+  *		radio.maskIRQ(1,1,0);
+  * @endcode
+  *
+  * @param tx_ok  Mask transmission complete interrupts
+  * @param tx_fail  Mask transmit failure interrupts
+  * @param rx_ready Mask payload received interrupts
   */
   void maskIRQ(bool tx_ok,bool tx_fail,bool rx_ready);
 
@@ -995,7 +1017,8 @@ private:
  * - Changes to read() functionality have increased reliability and response
  * - Extended timeout periods have been added to aid in noisy or otherwise unreliable environments
  * - Delays have been removed where possible to ensure maximum efficiency
- * - Untested: Arduino Due and ATTiny 84/85 support: Do NOT #include <SPI.h> with ATTiny.
+ * - Full Due support with extended SPI functions
+ * - Initial ATTiny support added (Untested)
  * - More! See the links below and class documentation for more info.
  *
  * If issues are discovered with the documentation, please report them here: <a href="https://github.com/TMRh20/tmrh20.github.io/issues"> here</a>
@@ -1013,6 +1036,15 @@ private:
  * This chip uses the SPI bus, plus two chip control pins.  Remember that pin 10 must still remain an output, or
  * the SPI hardware will go into 'slave' mode.
  *
+ * @section BoardSupport Board Support
+ *
+ * Most standard Arduino based boards are supported:
+ * - ATMega 328 based boards (Uno, Nano, etc)
+ * - Mega Boards (1280, 2560, etc)
+ * - ARM based boards (Arduino Due)  Note: Do not include printf.h or use printf begin. This functionality is already present. Must use one of the
+ * 	hardware SS/CSN pins.
+ * - ATTiny boards (Not fully tested) Note: Do not include SPI.h. The SPI functions for ATTiny are already included.
+ *
  * @section More More Information
  *
  * @section Info and Projects

examples/pingpair_dyn/pingpair_dyn.ino

@@ -15,7 +15,7 @@
 #include <SPI.h>
 #include "nRF24L01.h"
 #include "RF24.h"
-#include "printf.h"
+//#include "printf.h"
 
 //
 // Hardware configuration
@@ -27,7 +27,7 @@ RF24 radio(9,10);
 
 // sets the role of this unit in hardware.  Connect to GND to be the 'pong' receiver
 // Leave open to be the 'ping' transmitter
-const int role_pin = 7;
+const int role_pin = 5;
 
 //
 // Topology
@@ -61,7 +61,7 @@ role_e role;
 
 const int min_payload_size = 4;
 const int max_payload_size = 32;
-const int payload_size_increments_by = 2;
+const int payload_size_increments_by = 1;
 int next_payload_size = min_payload_size;
 
 char receive_payload[max_payload_size+1]; // +1 to allow room for a terminating NULL char
@@ -74,7 +74,7 @@ void setup(void)
 
   // set up the role pin
   pinMode(role_pin, INPUT);
-  digitalWrite(role_pin,HIGH);
+  digitalWrite(role_pin,LOW);
   delay(20); // Just to get a solid reading on the role pin
 
   // read the address pin, establish our role
@@ -88,7 +88,7 @@ void setup(void)
   //
 
   Serial.begin(57600);
-  printf_begin();
+  //printf_begin();
   printf("\n\rRF24/examples/pingpair_dyn/\n\r");
   printf("ROLE: %s\n\r",role_friendly_name[role]);
 
@@ -102,7 +102,7 @@ void setup(void)
   radio.enableDynamicPayloads();
 
   // optionally, increase the delay between retries & # of retries
-  radio.setRetries(15,15);
+  radio.setRetries(5,15);
 
   //
   // Open pipes to other nodes for communication
@@ -189,7 +189,7 @@ void loop(void)
       next_payload_size = min_payload_size;
 
     // Try again 1s later
-    delay(1000);
+    delay(100);
   }
 
   //
@@ -204,11 +204,11 @@ void loop(void)
       // Dump the payloads until we've gotten everything
       uint8_t len;
       bool done = false;
-      while (!done)
+      while (radio.available())
       {
         // Fetch the payload, and see if this was the last one.
 	len = radio.getDynamicPayloadSize();
-	done = radio.read( receive_payload, len );
+	radio.read( receive_payload, len );
 
 	// Put a zero at the end for easy printing
 	receive_payload[len] = 0;