add Wire::onRequestMore()

libraries/Wire/src/Wire.cpp

@@ -43,6 +43,7 @@ uint8_t TwoWire::txBufferLength = 0;
 
 uint8_t TwoWire::transmitting = 0;
 void (*TwoWire::user_onRequest)(void);
+void (*TwoWire::user_onRequestMore)(void);
 void (*TwoWire::user_onReceive)(int);
 
 // Constructors ////////////////////////////////////////////////////////////////
@@ -63,6 +64,7 @@ void TwoWire::begin(void)
 
   twi_init();
   twi_attachSlaveTxEvent(onRequestService); // default callback must exist
+  twi_attachSlaveTxMoreEvent(onRequestMoreService); // default callback must exist
   twi_attachSlaveRxEvent(onReceiveService); // default callback must exist
 }
 
@@ -360,6 +362,17 @@ void TwoWire::onRequestService(void)
   user_onRequest();
 }
 
+// behind the scenes function that is called when more data is requested
+void TwoWire::onRequestMoreService(void)
+{
+  // don't bother if user hasn't registered a callback
+  if(!user_onRequestMore){
+    return;
+  }
+  // alert user program
+  user_onRequestMore();
+}
+
 // sets function called on slave write
 void TwoWire::onReceive( void (*function)(int) )
 {
@@ -372,6 +385,12 @@ void TwoWire::onRequest( void (*function)(void) )
   user_onRequest = function;
 }
 
+// sets function called on slave read
+void TwoWire::onRequestMore( void (*function)(void) )
+{
+  user_onRequestMore = function;
+}
+
 // Preinstantiate Objects //////////////////////////////////////////////////////
 
 TwoWire Wire = TwoWire();

libraries/Wire/src/Wire.h

@@ -45,8 +45,10 @@ class TwoWire : public Stream
 
     static uint8_t transmitting;
     static void (*user_onRequest)(void);
+    static void (*user_onRequestMore)(void);
     static void (*user_onReceive)(int);
     static void onRequestService(void);
+    static void onRequestMoreService(void);
     static void onReceiveService(uint8_t*, int);
   public:
     TwoWire();
@@ -75,6 +77,7 @@ class TwoWire : public Stream
     virtual void flush(void);
     void onReceive( void (*)(int) );
     void onRequest( void (*)(void) );
+    void onRequestMore( void (*)(void) );
 
     inline size_t write(unsigned long n) { return write((uint8_t)n); }
     inline size_t write(long n) { return write((uint8_t)n); }

libraries/Wire/src/utility/twi.c

@@ -56,6 +56,7 @@ static volatile bool twi_timed_out_flag = false;  // a timeout has been seen
 static volatile bool twi_do_reset_on_timeout = false;  // reset the TWI registers on timeout
 
 static void (*twi_onSlaveTransmit)(void);
+static void (*twi_onSlaveTransmitMore)(void);
 static void (*twi_onSlaveReceive)(uint8_t*, int);
 
 static uint8_t twi_masterBuffer[TWI_BUFFER_LENGTH];
@@ -384,6 +385,17 @@ void twi_attachSlaveTxEvent( void (*function)(void) )
   twi_onSlaveTransmit = function;
 }
 
+/* 
+ * Function twi_attachSlaveTxMoreEvent
+ * Desc     sets function called before a slave cont'd sequential data write operation
+ * Input    function: callback function to use
+ * Output   none
+ */
+void twi_attachSlaveTxMoreEvent( void (*function)(void) )
+{
+  twi_onSlaveTransmitMore = function;
+}
+
 /* 
  * Function twi_reply
  * Desc     sends byte or readys receive line
@@ -640,6 +652,10 @@ ISR(TWI_vect)
     case TW_ST_DATA_ACK: // byte sent, ack returned
       // copy data to output register
       TWDR = twi_txBuffer[twi_txBufferIndex++];
+	  // if the buffer emptied, request it to be topped up
+	  if (twi_txBufferIndex >= twi_txBufferLength) {
+		twi_onSlaveTransmitMore();
+	  }
       // if there is more to send, ack, otherwise nack
       if(twi_txBufferIndex < twi_txBufferLength){
         twi_reply(1);

libraries/Wire/src/utility/twi.h

@@ -49,6 +49,7 @@
   uint8_t twi_transmit(const uint8_t*, uint8_t);
   void twi_attachSlaveRxEvent( void (*)(uint8_t*, int) );
   void twi_attachSlaveTxEvent( void (*)(void) );
+  void twi_attachSlaveTxMoreEvent( void (*)(void) );
   void twi_reply(uint8_t);
   void twi_stop(void);
   void twi_releaseBus(void);