Create R2D2 Easy Transfer

R2D2 Easy Transfer

@@ -0,0 +1,84 @@
+#include "EasyTransfer.h"
+
+
+
+
+//Captures address and size of struct
+void EasyTransfer::begin(uint8_t * ptr, uint8_t length, HardwareSerial *theSerial){
+address = ptr;
+size = length;
+_serial = theSerial;
+}
+
+//Sends out struct in binary, with header, length info and checksum
+void EasyTransfer::sendData(){
+  uint8_t CS = size;
+  _serial->write(0x06);
+  _serial->write(0x85);
+  _serial->write(size);
+  for(int i = 0; i<size; i++){
+    CS^=*(address+i);
+    _serial->write(*(address+i));
+  }
+  _serial->write(CS);
+
+}
+
+boolean EasyTransfer::receiveData(){
+
+  //start off by looking for the header bytes. If they were already found in a previous call, skip it.
+  if(rx_len == 0){
+  //this size check may be redundant due to the size check below, but for now I'll leave it the way it is.
+    if(_serial->available() >= 3){
+	//this will block until a 0x06 is found or buffer size becomes less then 3.
+      while(_serial->read() != 0x06) {
+		//This will trash any preamble junk in the serial buffer
+		//but we need to make sure there is enough in the buffer to process while we trash the rest
+		//if the buffer becomes too empty, we will escape and try again on the next call
+		if(_serial->available() < 3)
+			return false;
+		}
+      if (_serial->read() == 0x85){
+        rx_len = _serial->read();
+		//make sure the binary structs on both Arduinos are the same size.
+        if(rx_len != size){
+          rx_len = 0;
+          return false;
+        }
+      }
+    }
+  }
+
+  //we get here if we already found the header bytes, the struct size matched what we know, and now we are byte aligned.
+  if(rx_len != 0){
+    while(_serial->available() && rx_array_inx <= rx_len){
+      rx_array[rx_array_inx++] = _serial->read();
+    }
+
+    if(rx_len == (rx_array_inx-1)){
+      //seem to have got whole message
+      //last uint8_t is CS
+      calc_CS = rx_len;
+      for (int i = 0; i<rx_len; i++){
+        calc_CS^=rx_array[i];
+      } 
+
+      if(calc_CS == rx_array[rx_array_inx-1]){//CS good
+        memcpy(address,&rx_array,size);
+		rx_len = 0;
+		rx_array_inx = 0;
+		return true;
+		}
+
+	  else{
+	  //failed checksum, need to clear this out anyway
+		rx_len = 0;
+		rx_array_inx = 0;
+		return false;
+	  }
+
+    }
+  }
+
+  return false;
+}