diff --git a/software/SCSI2SD/src/config.c b/software/SCSI2SD/src/config.c
index e7176e8..23bdf47 100755
--- a/software/SCSI2SD/src/config.c
+++ b/software/SCSI2SD/src/config.c
@@ -58,6 +58,7 @@ enum USB_STATE
 };
 
 static uint8_t hidBuffer[USBHID_LEN];
+static uint8_t dbgHidBuffer[USBHID_LEN];
 
 static int usbInEpState;
 static int usbDebugEpState;
@@ -356,6 +357,7 @@ void configPoll()
 
 	if (reset)
 	{
+        hidPacket_reset();
 		USBFS_EnableOutEP(USB_EP_OUT);
 		USBFS_EnableOutEP(USB_EP_COMMAND);
 		usbInEpState = usbDebugEpState = USB_IDLE;
@@ -363,24 +365,32 @@ void configPoll()
 
 	if(USBFS_GetEPState(USB_EP_OUT) == USBFS_OUT_BUFFER_FULL)
 	{
-		ledOn();
-
 		// The host sent us some data!
 		int byteCount = USBFS_GetEPCount(USB_EP_OUT);
 		USBFS_ReadOutEP(USB_EP_OUT, hidBuffer, sizeof(hidBuffer));
 		hidPacket_recv(hidBuffer, byteCount);
-
+        
+        size_t cmdSize;
+        if (hidPacket_peekPacket(&cmdSize) == NULL)
+        {
+            // Allow the host to send us another updated config.
+		    USBFS_EnableOutEP(USB_EP_OUT);
+        }
+    }
+    
+    if (hidPacket_getHIDBytesReady() == 0) // Nothing queued to send
+    {
 		size_t cmdSize;
 		const uint8_t* cmd = hidPacket_getPacket(&cmdSize);
 		if (cmd && (cmdSize > 0))
 		{
+            ledOn();
 			processCommand(cmd, cmdSize);
+            ledOff();
+            
+            // Allow the host to send us another updated config.
+		    USBFS_EnableOutEP(USB_EP_OUT);
 		}
-
-		// Allow the host to send us another updated config.
-		USBFS_EnableOutEP(USB_EP_OUT);
-
-		ledOff();
 	}
 
 	switch (usbInEpState)
@@ -418,10 +428,10 @@ void debugPoll()
 	{
 		// The host sent us some data!
 		int byteCount = USBFS_GetEPCount(USB_EP_COMMAND);
-		USBFS_ReadOutEP(USB_EP_COMMAND, (uint8 *)&hidBuffer, byteCount);
+		USBFS_ReadOutEP(USB_EP_COMMAND, (uint8 *)&dbgHidBuffer, byteCount);
 
 		if (byteCount >= 1 &&
-			hidBuffer[0] == 0x01)
+			dbgHidBuffer[0] == 0x01)
 		{
 			// Reboot command.
 			Bootloadable_1_Load();
@@ -435,36 +445,36 @@ void debugPoll()
 	switch (usbDebugEpState)
 	{
 	case USB_IDLE:
-		memcpy(&hidBuffer, &scsiDev.cdb, 12);
-		hidBuffer[12] = scsiDev.msgIn;
-		hidBuffer[13] = scsiDev.msgOut;
-		hidBuffer[14] = scsiDev.lastStatus;
-		hidBuffer[15] = scsiDev.lastSense;
-		hidBuffer[16] = scsiDev.phase;
-		hidBuffer[17] = SCSI_ReadFilt(SCSI_Filt_BSY);
-		hidBuffer[18] = SCSI_ReadFilt(SCSI_Filt_SEL);
-		hidBuffer[19] = SCSI_ReadFilt(SCSI_Filt_ATN);
-		hidBuffer[20] = SCSI_ReadFilt(SCSI_Filt_RST);
-		hidBuffer[21] = scsiDev.rstCount;
-		hidBuffer[22] = scsiDev.selCount;
-		hidBuffer[23] = scsiDev.msgCount;
-		hidBuffer[24] = scsiDev.cmdCount;
-		hidBuffer[25] = scsiDev.watchdogTick;
-		hidBuffer[26] = 0; // OBSOLETE. Previously media state
-		hidBuffer[27] = scsiDev.lastSenseASC >> 8;
-		hidBuffer[28] = scsiDev.lastSenseASC;
-		hidBuffer[29] = scsiReadDBxPins();
-		hidBuffer[30] = LastTrace;
+		memcpy(&dbgHidBuffer, &scsiDev.cdb, 12);
+		dbgHidBuffer[12] = scsiDev.msgIn;
+		dbgHidBuffer[13] = scsiDev.msgOut;
+		dbgHidBuffer[14] = scsiDev.lastStatus;
+		dbgHidBuffer[15] = scsiDev.lastSense;
+		dbgHidBuffer[16] = scsiDev.phase;
+		dbgHidBuffer[17] = SCSI_ReadFilt(SCSI_Filt_BSY);
+		dbgHidBuffer[18] = SCSI_ReadFilt(SCSI_Filt_SEL);
+		dbgHidBuffer[19] = SCSI_ReadFilt(SCSI_Filt_ATN);
+		dbgHidBuffer[20] = SCSI_ReadFilt(SCSI_Filt_RST);
+		dbgHidBuffer[21] = scsiDev.rstCount;
+		dbgHidBuffer[22] = scsiDev.selCount;
+		dbgHidBuffer[23] = scsiDev.msgCount;
+		dbgHidBuffer[24] = scsiDev.cmdCount;
+		dbgHidBuffer[25] = scsiDev.watchdogTick;
+		dbgHidBuffer[26] = 0; // OBSOLETE. Previously media state
+		dbgHidBuffer[27] = scsiDev.lastSenseASC >> 8;
+		dbgHidBuffer[28] = scsiDev.lastSenseASC;
+		dbgHidBuffer[29] = scsiReadDBxPins();
+		dbgHidBuffer[30] = LastTrace;
 
-		hidBuffer[58] = sdCard.capacity >> 24;
-		hidBuffer[59] = sdCard.capacity >> 16;
-		hidBuffer[60] = sdCard.capacity >> 8;
-		hidBuffer[61] = sdCard.capacity;
+		dbgHidBuffer[58] = sdCard.capacity >> 24;
+		dbgHidBuffer[59] = sdCard.capacity >> 16;
+		dbgHidBuffer[60] = sdCard.capacity >> 8;
+		dbgHidBuffer[61] = sdCard.capacity;
 
-		hidBuffer[62] = FIRMWARE_VERSION >> 8;
-		hidBuffer[63] = FIRMWARE_VERSION;
+		dbgHidBuffer[62] = FIRMWARE_VERSION >> 8;
+		dbgHidBuffer[63] = FIRMWARE_VERSION;
 
-		USBFS_LoadInEP(USB_EP_DEBUG, (uint8 *)&hidBuffer, sizeof(hidBuffer));
+		USBFS_LoadInEP(USB_EP_DEBUG, (uint8 *)&dbgHidBuffer, sizeof(dbgHidBuffer));
 		usbDebugEpState = USB_DATA_SENT;
 		break;
 
diff --git a/software/SCSI2SD/src/hidpacket.c b/software/SCSI2SD/src/hidpacket.c
index 8fe484a..36d14c4 100644
--- a/software/SCSI2SD/src/hidpacket.c
+++ b/software/SCSI2SD/src/hidpacket.c
@@ -45,6 +45,12 @@ txReset()
 	tx.offset = 0;
 }
 
+void hidPacket_reset()
+{
+    rxReset();
+    txReset();
+}
+
 void hidPacket_recv(const uint8_t* bytes, size_t len)
 {
 	if (len < 2)
@@ -94,6 +100,21 @@ void hidPacket_recv(const uint8_t* bytes, size_t len)
 	}
 }
 
+const uint8_t*
+hidPacket_peekPacket(size_t* len)
+{
+	if (rx.state == COMPLETE)
+	{
+		*len = rx.offset;
+		return rx.buffer;
+	}
+	else
+	{
+		*len = 0;
+		return NULL;
+	}
+}
+
 const uint8_t*
 hidPacket_getPacket(size_t* len)
 {
@@ -125,6 +146,17 @@ void hidPacket_send(const uint8_t* bytes, size_t len)
 	}
 }
 
+int
+hidPacket_getHIDBytesReady()
+{
+	if ((tx.state != PARTIAL) || (tx.offset <= 0))
+	{
+		return 0;
+	}
+
+	return 1;
+}
+
 const uint8_t*
 hidPacket_getHIDBytes(uint8_t* hidBuffer)
 {
diff --git a/software/SCSI2SD/src/main.c b/software/SCSI2SD/src/main.c
index 5e93e70..b9a6215 100755
--- a/software/SCSI2SD/src/main.c
+++ b/software/SCSI2SD/src/main.c
@@ -18,6 +18,7 @@
 #include "scsi.h"
 #include "scsiPhy.h"
 #include "config.h"
+#include "debug.h"
 #include "disk.h"
 #include "led.h"
 #include "time.h"
@@ -79,7 +80,11 @@ int main()
 				scsiPhyConfig();
 				scsiInit();
 			}
-			else
+            
+            // If USB is connected we could be busy transferring data
+            // Note: The same flag is used for the config USB interface and
+            // therefore SPI flash writes
+			else if (!isDebugEnabled())
 			{
 				// Wait for our 1ms timer to save some power.
 				// There's an interrupt on the SEL signal to ensure we respond
diff --git a/software/SCSI2SD/src/sd.c b/software/SCSI2SD/src/sd.c
index 536318a..e1056ab 100755
--- a/software/SCSI2SD/src/sd.c
+++ b/software/SCSI2SD/src/sd.c
@@ -993,10 +993,10 @@ void sdCheckPresent()
 		SD_CS_Write(0);
 		SD_CS_SetDriveMode(SD_CS_DM_DIG_HIZ);
 
-		// Delay extended to work with 60cm cables running cards at 2.85V
-		CyDelayCycles(128);
+		// Delay reduced for v5.2 board, no support for extension cables.
+		CyDelayCycles(32);
 		uint8_t cs = SD_CS_Read();
-		SD_CS_SetDriveMode(SD_CS_DM_STRONG)	;
+		SD_CS_SetDriveMode(SD_CS_DM_STRONG);
 
 		if (cs && !(sdCard.dev.mediaState & MEDIA_PRESENT))
 		{
diff --git a/software/SCSI2SD/v5.2/SCSI2SD.cydsn/SCSI2SD.cyfit b/software/SCSI2SD/v5.2/SCSI2SD.cydsn/SCSI2SD.cyfit
index 735b8f8..76c7733 100644
Binary files a/software/SCSI2SD/v5.2/SCSI2SD.cydsn/SCSI2SD.cyfit and b/software/SCSI2SD/v5.2/SCSI2SD.cydsn/SCSI2SD.cyfit differ
diff --git a/software/include/hidpacket.h b/software/include/hidpacket.h
index d0ea3d8..85a8334 100644
--- a/software/include/hidpacket.h
+++ b/software/include/hidpacket.h
@@ -42,6 +42,10 @@ void hidPacket_recv(const uint8_t* bytes, size_t len);
 // available.
 const uint8_t* hidPacket_getPacket(size_t* len);
 
+// Returns the received packet contents, or NULL if a complete packet isn't
+// available. Does not modify state
+const uint8_t* hidPacket_peekPacket(size_t* len);
+
 // Call this with packet data to send. len <= USBHID_LEN
 // Overwrites any packet currently being sent.
 void hidPacket_send(const uint8_t* bytes, size_t len);
@@ -50,6 +54,11 @@ void hidPacket_send(const uint8_t* bytes, size_t len);
 // NULL if there's nothing to send.
 const uint8_t* hidPacket_getHIDBytes(uint8_t* hidBuffer);
 
+// Returns 1 if hidPacket_getHIDBytes will return non-null
+int hidPacket_getHIDBytesReady();
+
+void hidPacket_reset();
+
 #ifdef __cplusplus
 } // extern "C"
 #endif