Wire: release the bus on error

Author: Marti Bolivar

libraries/Wire/Wire.cpp

@@ -128,6 +128,7 @@ uint8 TwoWire::process() {
     // shift out the address we're transmitting to
     i2c_shift_out(sla_addr);
     if (!i2c_get_ack()) {
+        i2c_stop();             // Fix up the state of the bus
         return ENACKADDR;
     }
     // Recieving
@@ -146,6 +147,7 @@ uint8 TwoWire::process() {
         for (uint8 i = 0; i < itc_msg.length; i++) {
             i2c_shift_out(itc_msg.data[i]);
             if (!i2c_get_ack()) {
+                i2c_stop();     // Fix up the state of the bus
                 return ENACKTRNS;
             }
             itc_msg.xferred++;