Implement dynamic payloads, with an example

RF24.cpp

@@ -111,11 +111,11 @@ uint8_t RF24::write_payload(const void* buf, uint8_t len)
   csn(LOW);
   status = SPI.transfer( W_TX_PAYLOAD );
   uint8_t data_len = min(len,payload_size);
-  uint8_t blank_len = payload_size - data_len;
+  //uint8_t blank_len = payload_size - data_len;
   while ( data_len-- )
     SPI.transfer(*current++);
-  while ( blank_len-- )
-    SPI.transfer(0);
+  //while ( blank_len-- )
+  //  SPI.transfer(0);
 
   csn(HIGH);
 
@@ -132,11 +132,11 @@ uint8_t RF24::read_payload(void* buf, uint8_t len)
   csn(LOW);
   status = SPI.transfer( R_RX_PAYLOAD );
   uint8_t data_len = min(len,payload_size);
-  uint8_t blank_len = payload_size - data_len;
+  //uint8_t blank_len = payload_size - data_len;
   while ( data_len-- )
     *current++ = SPI.transfer(0xff);
-  while ( blank_len-- )
-    SPI.transfer(0xff);
+  //while ( blank_len-- )
+  //  SPI.transfer(0xff);
   csn(HIGH);
 
   return status;
@@ -396,7 +396,7 @@ boolean RF24::write( const void* buf, uint8_t len )
   // Handle the ack packet
   if ( ack_payload_available )
   {
-    ack_payload_length = read_payload_length();
+    ack_payload_length = getDynamicPayloadSize();
     IF_SERIAL_DEBUG(Serial.print("[AckPacket]/"));
     IF_SERIAL_DEBUG(Serial.println(ack_payload_length,DEC));
   }
@@ -430,7 +430,7 @@ void RF24::startWrite( const void* buf, uint8_t len )
 
 /******************************************************************/
 
-uint8_t RF24::read_payload_length(void)
+uint8_t RF24::getDynamicPayloadSize(void)
 {
   uint8_t result = 0;
 
@@ -577,6 +577,30 @@ void RF24::toggle_features(void)
 
 /******************************************************************/
 
+void RF24::enableDynamicPayloads(void)
+{
+  // Enable dynamic payload throughout the system
+  write_register(FEATURE,read_register(FEATURE) | _BV(EN_DPL) );
+
+  // If it didn't work, the features are not enabled
+  if ( ! read_register(FEATURE) )
+  {
+    // So enable them and try again
+    toggle_features();
+    write_register(FEATURE,read_register(FEATURE) | _BV(EN_DPL) );
+  }
+
+  IF_SERIAL_DEBUG(printf("FEATURE=%i\n\r",read_register(FEATURE)));
+
+  // Enable dynamic payload on all pipes
+  //
+  // Not sure the use case of only having dynamic payload on certain
+  // pipes, so the library does not support it.
+  write_register(DYNPD,read_register(DYNPD) | _BV(DPL_P5) | _BV(DPL_P4) | _BV(DPL_P3) | _BV(DPL_P2) | _BV(DPL_P1) | _BV(DPL_P0));
+}
+
+/******************************************************************/
+
 void RF24::enableAckPayload(void)
 {
   //
@@ -596,7 +620,7 @@ void RF24::enableAckPayload(void)
   IF_SERIAL_DEBUG(printf("FEATURE=%i\n\r",read_register(FEATURE)));
 
   //
-  // Enable dynamic payload on pipe 0
+  // Enable dynamic payload on pipes 0 & 1
   //
 
   write_register(DYNPD,read_register(DYNPD) | _BV(DPL_P1) | _BV(DPL_P0));

RF24.h

@@ -112,16 +112,6 @@ protected:
    */
   uint8_t read_payload(void* buf, uint8_t len);
 
-  /**
-   * Read the payload length
-   *
-   * For dynamic payloads, this pulls the size of the payload off
-   * the chip
-   *
-   * @return Payload length of last-received dynamic payload
-   */
-  uint8_t read_payload_length(void);
-
   /**
    * Empty the receive buffer
    *
@@ -352,7 +342,7 @@ public:
   void setChannel(uint8_t channel);
 
   /**
-   * Set Payload Size
+   * Set Static Payload Size
    *
    * This implementation uses a pre-stablished fixed payload size for all
    * transmissions.  If this method is never called, the driver will always
@@ -366,7 +356,7 @@ public:
   void setPayloadSize(uint8_t size);
 
   /**
-   * Get Payload Size
+   * Get Static Payload Size
    *
    * @see setPayloadSize()
    *
@@ -374,6 +364,16 @@ public:
    */
   uint8_t getPayloadSize(void);
 
+  /**
+   * Get Dynamic Payload Size 
+   *
+   * For dynamic payloads, this pulls the size of the payload off
+   * the chip
+   *
+   * @return Payload length of last-received dynamic payload
+   */
+  uint8_t getDynamicPayloadSize(void);
+
   /**
    * Print a giant block of debugging information to stdout
    *
@@ -425,6 +425,16 @@ public:
    */
   void enableAckPayload(void);
 
+  /**
+   * Enable dynamically-sized payloads
+   *
+   * This way you don't always have to send large packets just to send them
+   * once in a while.  This enables dynamic payloads on ALL pipes.
+   *
+   * @see examples/pingpair_pl/pingpair_dyn.pde
+   */
+  void enableDynamicPayloads(void);
+
   /**
    * Write an ack payload for the specified pipe
    *

examples/pingpair_dyn/pingpair_dyn.pde

@@ -55,6 +55,17 @@ const char* role_friendly_name[] = { "invalid", "Ping out", "Pong back"};
 // The role of the current running sketch
 role_e role;
 
+//
+// Payload
+//
+
+const int min_payload_size = 4;
+const int max_payload_size = 32;
+const int payload_size_increments_by = 2;
+int next_payload_size = min_payload_size;
+
+char receive_payload[max_payload_size+1]; // +1 to allow room for a terminating NULL char
+
 void setup(void)
 {
   //
@@ -87,6 +98,9 @@ void setup(void)
 
   radio.begin();
 
+  // enable dynamic payloads
+  radio.enableDynamicPayloads();
+
   // optionally, increase the delay between retries & # of retries
   radio.setRetries(15,15);
 
@@ -137,22 +151,24 @@ void loop(void)
 
   if (role == role_ping_out)
   {
+    // The payload will always be the same, what will change is how much of it we send.
+    static char send_payload[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ789012";
+
     // First, stop listening so we can talk.
     radio.stopListening();
 
     // Take the time, and send it.  This will block until complete
-    unsigned long time = millis();
-    printf("Now sending %lu...",time);
-    radio.write( &time, sizeof(unsigned long) );
+    printf("Now sending length %i...",next_payload_size);
+    radio.write( send_payload, next_payload_size );
 
     // Now, continue listening
     radio.startListening();
 
-    // Wait here until we get a response, or timeout (250ms)
+    // Wait here until we get a response, or timeout
     unsigned long started_waiting_at = millis();
     bool timeout = false;
     while ( ! radio.available() && ! timeout )
-      if (millis() - started_waiting_at > 250 )
+      if (millis() - started_waiting_at > 500 )
         timeout = true;
 
     // Describe the results
@@ -163,12 +179,20 @@ void loop(void)
     else
     {
       // Grab the response, compare, and send to debugging spew
-      unsigned long got_time;
-      radio.read( &got_time, sizeof(unsigned long) );
+      uint8_t len = radio.getDynamicPayloadSize();
+      radio.read( receive_payload, len );
+
+      // Put a zero at the end for easy printing
+      receive_payload[len] = 0;
 
       // Spew it
-      printf("Got response %lu, round-trip delay: %lu\n\r",got_time,millis()-got_time);
+      printf("Got response size=%i value=%s\n\r",len,receive_payload);
     }
+    
+    // Update size for next time.
+    next_payload_size += payload_size_increments_by;
+    if ( next_payload_size > max_payload_size )
+      next_payload_size = min_payload_size;
 
     // Try again 1s later
     delay(1000);
@@ -184,22 +208,26 @@ void loop(void)
     if ( radio.available() )
     {
       // Dump the payloads until we've gotten everything
-      unsigned long got_time;
+      uint8_t len;
       boolean done = false;
       while (!done)
       {
         // Fetch the payload, and see if this was the last one.
-        done = radio.read( &got_time, sizeof(unsigned long) );
+	len = radio.getDynamicPayloadSize();
+	done = radio.read( receive_payload, len );
+
+	// Put a zero at the end for easy printing
+	receive_payload[len] = 0;
 
-        // Spew it
-        printf("Got payload %lu...",got_time);
+	// Spew it
+	printf("Got payload size=%i value=%s\n\r",len,receive_payload);
       }
 
       // First, stop listening so we can talk
       radio.stopListening();
 
       // Send the final one back.
-      radio.write( &got_time, sizeof(unsigned long) );
+      radio.write( receive_payload, len );
       printf("Sent response.\n\r");
 
       // Now, resume listening so we catch the next packets.