If ::begin() is called on a port that is already open, preserve the previous buffer settings. This makes it easy to change serial speeds without having to know how the port buffers were set up originally.

git-svn-id: https://arducopter.googlecode.com/svn/trunk@672 f9c3cf11-9bcb-44bc-f272-b75c42450872

libraries/FastSerial/FastSerial.cpp

@@ -116,6 +116,18 @@ FastSerial::FastSerial(const uint8_t portNumber,
 
 void FastSerial::begin(long baud)
 {
+        unsigned int    rxb, txb;
+
+        // If we are re-configuring an already-open port, preserve the
+        // existing buffer sizes.
+        if (_open) {
+                rxb = _rxBuffer->mask + 1;
+                txb = _txBuffer->mask + 1;
+        } else {
+                rxb = RX_BUFFER_SIZE;
+                txb = TX_BUFFER_SIZE;
+        }
+
         begin(baud, RX_BUFFER_SIZE, TX_BUFFER_SIZE);
 }