Merge pull request #367 from DennisErnst/master

Fix hangs when transfer errors occur

Author: hathach

cores/arduino/SERCOM.cpp

@@ -556,29 +556,35 @@ bool SERCOM::startTransmissionWIRE(uint8_t address, SercomWireReadWriteFlag flag
   // Address Transmitted
   if ( flag == WIRE_WRITE_FLAG ) // Write mode
   {
-    while( !sercom->I2CM.INTFLAG.bit.MB )
-    {
+    while( !sercom->I2CM.INTFLAG.bit.MB ) {
       // Wait transmission complete
+
+      // If certain errors occur, the MB bit may never be set (RFTM: SAMD21 sec:28.10.6; SAMD51 sec:36.10.7).
+      // The data transfer errors that can occur (including BUSERR) are all
+      // rolled up into INTFLAG.bit.ERROR from STATUS.reg
+      if (sercom->I2CM.INTFLAG.bit.ERROR) {
+        return false;
+      }
     }
   }
   else  // Read mode
   {
-    while( !sercom->I2CM.INTFLAG.bit.SB )
-    {
-        // If the slave NACKS the address, the MB bit will be set.
-        // In that case, send a stop condition and return false.
-        if (sercom->I2CM.INTFLAG.bit.MB) {
-            sercom->I2CM.CTRLB.bit.CMD = 3; // Stop condition
-            return false;
-        }
+    while( !sercom->I2CM.INTFLAG.bit.SB ) {
       // Wait transmission complete
+
+      // If the slave NACKS the address, the MB bit will be set.
+      // A variety of errors in the STATUS register can set the ERROR bit in the INTFLAG register
+      // In that case, send a stop condition and return false.
+      if (sercom->I2CM.INTFLAG.bit.MB || sercom->I2CM.INTFLAG.bit.ERROR) {
+        sercom->I2CM.CTRLB.bit.CMD = 3; // Stop condition
+        return false;
+      }
     }
 
     // Clean the 'Slave on Bus' flag, for further usage.
     //sercom->I2CM.INTFLAG.bit.SB = 0x1ul;
   }
 
-
   //ACK received (0: ACK, 1: NACK)
   if(sercom->I2CM.STATUS.bit.RXNACK)
   {
@@ -597,10 +603,11 @@ bool SERCOM::sendDataMasterWIRE(uint8_t data)
 
   //Wait transmission successful
   while(!sercom->I2CM.INTFLAG.bit.MB) {
-
-    // If a bus error occurs, the MB bit may never be set.
-    // Check the bus error bit and bail if it's set.
-    if (sercom->I2CM.STATUS.bit.BUSERR) {
+    // If a data transfer error occurs, the MB bit may never be set.
+    // Check the error bit and bail if it's set.
+    // The data transfer errors that can occur (including BUSERR) are all
+    // rolled up into INTFLAG.bit.ERROR from STATUS.reg
+    if (sercom->I2CM.INTFLAG.bit.ERROR) {
       return false;
     }
   }
@@ -701,9 +708,17 @@ uint8_t SERCOM::readDataWIRE( void )
 {
   if(isMasterWIRE())
   {
-    while( sercom->I2CM.INTFLAG.bit.SB == 0 )
-    {
+    while (sercom->I2CM.INTFLAG.bit.SB == 0) {
       // Waiting complete receive
+      // A variety of errors in the STATUS register can set the ERROR bit in the INTFLAG register
+      // In that case, send a stop condition and return false.
+      // readDataWIRE should really be able to indicate an error (which would never be used
+      // because the readDataWIRE callers (in Wire.cpp) should have checked availableWIRE() first and timed it
+      // out if the data never showed up
+      if (sercom->I2CM.INTFLAG.bit.MB || sercom->I2CM.INTFLAG.bit.ERROR) {
+        sercom->I2CM.CTRLB.bit.CMD = 3; // Stop condition
+        return 0xFF;
+      }
     }
 
     return sercom->I2CM.DATA.bit.DATA ;