600 Baud comm. support, unsupported baudrate notification

- Added a 600 Baud line in DELAY_TABLE, for each CPU frequency.
(successfully tested for 16 MHz)

- begin(long speed) now returns a bool indicating if speed has been
found in DELAY_TABLE (if not, the method returns false immediately)

Author: sebastienjean

libraries/SoftwareSerial/SoftwareSerial.cpp

@@ -40,8 +40,8 @@ The latest version of this library can always be found at
 // 
 #include <avr/interrupt.h>
 #include <avr/pgmspace.h>
-#include "Arduino.h"
-#include "SoftwareSerial.h"
+#include <Arduino.h>
+#include <SoftwareSerial.h>
 //
 // Lookup table
 //
@@ -70,6 +70,7 @@ static const DELAY_TABLE PROGMEM table[] =
   { 4800,     233,       474,       474,      471,   },
   { 2400,     471,       950,       950,      947,   },
   { 1200,     947,       1902,      1902,     1899,  },
+  { 600,      1902,      3804,      3804,     3800,  },
   { 300,      3804,      7617,      7617,     7614,  },
 };
 
@@ -91,6 +92,7 @@ static const DELAY_TABLE table[] PROGMEM =
   { 4800,     110,        233,       233,    230,    },
   { 2400,     229,        472,       472,    469,    },
   { 1200,     467,        948,       948,    945,    },
+  { 600,      948,        1895,      1895,   1890,   },
   { 300,      1895,       3805,      3805,   3802,   },
 };
 
@@ -115,6 +117,7 @@ static const DELAY_TABLE PROGMEM table[] =
   { 4800,     296,        595,       595,    592,    },
   { 2400,     592,        1189,      1189,   1186,   },
   { 1200,     1187,       2379,      2379,   2376,   },
+  { 600,      2379,       4759,      4759,   4755,   },
   { 300,      4759,       9523,      9523,   9520,   },
 };
 
@@ -373,13 +376,15 @@ void SoftwareSerial::setRX(uint8_t rx)
 // Public methods
 //
 
-void SoftwareSerial::begin(long speed)
+bool SoftwareSerial::begin(long speed)
 {
   _rx_delay_centering = _rx_delay_intrabit = _rx_delay_stopbit = _tx_delay = 0;
 
+  long baud = 0;
+
   for (unsigned i=0; i<sizeof(table)/sizeof(table[0]); ++i)
   {
-    long baud = pgm_read_dword(&table[i].baud);
+    baud = pgm_read_dword(&table[i].baud);
     if (baud == speed)
     {
       _rx_delay_centering = pgm_read_word(&table[i].rx_delay_centering);
@@ -389,6 +394,7 @@ void SoftwareSerial::begin(long speed)
       break;
     }
   }
+  if (baud != speed) return false;
 
   // Set up RX interrupts, but only if we have a valid RX baud rate
   if (_rx_delay_stopbit)
@@ -407,6 +413,8 @@ void SoftwareSerial::begin(long speed)
 #endif
 
   listen();
+
+  return true;
 }
 
 void SoftwareSerial::end()

libraries/SoftwareSerial/SoftwareSerial.h

@@ -82,7 +82,7 @@ class SoftwareSerial : public Stream
   // public methods
   SoftwareSerial(uint8_t receivePin, uint8_t transmitPin, bool inverse_logic = false);
   ~SoftwareSerial();
-  void begin(long speed);
+  bool begin(long speed);
   bool listen();
   void end();
   bool isListening() { return this == active_object; }