diff --git a/I2CManager_Wire.h b/I2CManager_Wire.h
index e8d5668..b8a6427 100644
--- a/I2CManager_Wire.h
+++ b/I2CManager_Wire.h
@@ -146,28 +146,36 @@ uint8_t I2CManagerClass::write_P(I2CAddress address, const uint8_t buffer[], uin
 uint8_t I2CManagerClass::read(I2CAddress address, uint8_t readBuffer[], uint8_t readSize,
                               const uint8_t writeBuffer[], uint8_t writeSize, I2CRB *rb)
 {
-  DIAG(F("I2CManagerClass::read()"));
+  // DIAG(F("Read addr=%x rdBuf=%x, rdLen=%d, wrBuf=%x, wrLen=%d"), address, readBuffer, readSize, writeBuffer, writeSize);
+  DIAG(F("I2CManagerClass::read() hit"));
   uint8_t status, muxStatus;
   uint8_t nBytes = 0;
   uint8_t retryCount = 0;
   // If request fails, retry up to the defined limit, unless the NORETRY flag is set
   // in the request block.
   do {
+    DIAG(F("do hit"));
     status = muxStatus = I2C_STATUS_OK;
+    DIAG(F("status=%d"),status);
 #ifdef I2C_EXTENDED_ADDRESS
+    DIAG(F("Extended address hit"));
     if (address.muxNumber() != I2CMux_None) {
       muxStatus = muxSelect(address);
     }
 #endif
     // Only start new transaction if address is non-zero.
     if (muxStatus == I2C_STATUS_OK && address != 0) {
+      DIAG(F("muxStatus=%d"),muxStatus);
       if (writeSize > 0) {
+        DIAG(F("wrBuf=%x, wrSize=%d"),writeBuffer,writeSize);
         Wire.beginTransmission(address);
         Wire.write(writeBuffer, writeSize);
         status = Wire.endTransmission(false); // Don't free bus yet
+        DIAG(F("status=%d"),status);
       }
       if (status == I2C_STATUS_OK) {
 #ifdef WIRE_HAS_TIMEOUT
+        DIAG(F("WIRE_HAS_TIMEOUT"));
         Wire.clearWireTimeoutFlag();
         Wire.requestFrom(address, (size_t)readSize);
         if (!Wire.getWireTimeoutFlag()) {
@@ -178,10 +186,14 @@ uint8_t I2CManagerClass::read(I2CAddress address, uint8_t readBuffer[], uint8_t
           status = I2C_STATUS_TIMEOUT;
         }
 #else
+        DIAG(F("NO timeout"));
         Wire.requestFrom(address, (size_t)readSize);
+          DIAG(F("address=%x, nBytes=%d, readSize=%d"),address,nBytes,readSize);
           while (Wire.available() && nBytes < readSize) 
             readBuffer[nBytes++] = Wire.read();
+            DIAG(F("nBytes=%d,readBuffer[nBytes]=%d"),nBytes-1,readBuffer[nBytes-1]);
           if (nBytes < readSize) status = I2C_STATUS_TRUNCATED;
+          DIAG(F("status=%d"),status);
 #endif
       }
     }
@@ -215,7 +227,7 @@ void I2CManagerClass::queueRequest(I2CRB *req) {
     DIAG(F("NOOOOOOOOOOO"));
     return;
   }
-  req->dump();
+  // req->dump();
   switch (req->operation & OPERATION_MASK) {
     case OPERATION_READ:
       read(req->i2cAddress, req->readBuffer, req->readLen, NULL, 0, req);
diff --git a/IO_EXIOExpander.h b/IO_EXIOExpander.h
index c8bcba0..fc59935 100644
--- a/IO_EXIOExpander.h
+++ b/IO_EXIOExpander.h
@@ -80,19 +80,24 @@ private:
   void _begin() {
     uint8_t status;
     // Initialise EX-IOExander device
+    DIAG(F("EXIO begin()"));
     I2CManager.begin();
     if (I2CManager.exists(_I2CAddress)) {
+      DIAG(F("EXIO address found %x"),_I2CAddress);
       // Send config, if EXIOPINS returned, we're good, setup pin buffers, otherwise go offline
       // NB The I2C calls here are done as blocking calls, as they're not time-critical
       // during initialisation and the reads require waiting for a response anyway.
       // Hence we can allocate I/O buffers from the stack.
       uint8_t receiveBuffer[3];
       uint8_t commandBuffer[4] = {EXIOINIT, (uint8_t)_nPins, (uint8_t)(_firstVpin & 0xFF), (uint8_t)(_firstVpin >> 8)};
+      DIAG(F("EXIOINIT, _nPins=%d, _firstVpin=%d"),_nPins,_firstVpin);
       status = I2CManager.read(_I2CAddress, receiveBuffer, sizeof(receiveBuffer), commandBuffer, sizeof(commandBuffer));
+      DIAG(F("EXIO status=%d"),status);
       if (status == I2C_STATUS_OK) {
         if (receiveBuffer[0] == EXIOPINS) {
           _numDigitalPins = receiveBuffer[1];
           _numAnaloguePins = receiveBuffer[2];
+          DIAG(F("EXIO dPins=%d, aPins=%d"),_numDigitalPins,_numAnaloguePins);
 
           // See if we already have suitable buffers assigned
           if (_numDigitalPins>0) {
@@ -208,6 +213,7 @@ private:
 
   // Main loop, collect both digital and analogue pin states continuously (faster sensor/input reads)
   void _loop(unsigned long currentMicros) override {
+    DIAG(F("EXIO _loop()"));
     if (_deviceState == DEVSTATE_FAILED) return;    // If device failed, return
 
     // Request block is used for analogue and digital reads from the IOExpander, which are performed
@@ -245,6 +251,7 @@ private:
         // Issue new read request for digital states.  As the request is non-blocking, the buffer has to
         // be allocated from heap (object state).
         _readCommandBuffer[0] = EXIORDD;
+        DIAG(F("EXIORDD address=%x, states=%d, bytes=%d"),_I2CAddress,_digitalInputStates,(_numDigitalPins+7)/8);
         I2CManager.read(_I2CAddress, _digitalInputStates, (_numDigitalPins+7)/8, _readCommandBuffer, 1, &_i2crb);
                                                                 // non-blocking read
         _lastDigitalRead = currentMicros;
@@ -252,6 +259,7 @@ private:
       } else if (currentMicros - _lastAnalogueRead > _analogueRefresh && _numAnaloguePins>0) { // Delay for analogue read refresh
         // Issue new read for analogue input states
         _readCommandBuffer[0] = EXIORDAN;
+        DIAG(F("EXIORDAN address=%x, aBuffer=%d, bytes=%d"),_I2CAddress,_analogueInputBuffer,_numAnaloguePins*2);
         I2CManager.read(_I2CAddress, _analogueInputBuffer,
             _numAnaloguePins * 2, _readCommandBuffer, 1, &_i2crb);
         _lastAnalogueRead = currentMicros;