fix SPI init issues as described http://code.google.com/p/arduino/issues/detail?id=888. Tested using qt1110 (mode 3) on a mega and WS5100 (webserver example sketch) chips on a etherten

Author: gandrewstone

libraries/SPI/SPI.cpp

@@ -14,27 +14,34 @@
 SPIClass SPI;
 
 void SPIClass::begin() {
-  // Set direction register for SCK and MOSI pin.
-  // MISO pin automatically overrides to INPUT.
+
+  // Set SS to high because many users use this as chip-select
+  // and most chips "select" when SS is high.  If your chip
+  // does not, you can set it back to LOW after begin() is called.
+  digitalWrite(SS, HIGH);
+
   // When the SS pin is set as OUTPUT, it can be used as
   // a general purpose output port (it doesn't influence
   // SPI operations).
-
-  pinMode(SCK, OUTPUT);
-  pinMode(MOSI, OUTPUT);
   pinMode(SS, OUTPUT);
-  
-  digitalWrite(SCK, LOW);
-  digitalWrite(MOSI, LOW);
-  digitalWrite(SS, HIGH);
 
-  // Warning: if the SS pin ever becomes a LOW INPUT then SPI 
-  // automatically switches to Slave, so the data direction of 
+  // Warning: if the SS pin ever becomes a LOW INPUT then SPI
+  // automatically switches to Slave, so the data direction of
   // the SS pin MUST be kept as OUTPUT.
   SPCR |= _BV(MSTR);
   SPCR |= _BV(SPE);
+
+  // Set direction register for SCK and MOSI pin.
+  // MISO pin automatically overrides to INPUT.
+  // By doing this AFTER enabling SPI, we avoid accidentally
+  // clocking in a single bit since the lines go directly
+  // from "input" to SPI control.  
+  // http://code.google.com/p/arduino/issues/detail?id=888
+  pinMode(SCK, OUTPUT);
+  pinMode(MOSI, OUTPUT);
 }
 
+
 void SPIClass::end() {
   SPCR &= ~_BV(SPE);
 }