Added verify during write. It seems to mostly work except when the chip

is completely removed from the SIMM -- in that case, the verification
still passes for some reason. I'm still debugging this one. Maybe the
data I had just written is still essentially on the bus because of the
floating pins and it reads it too fast? Maybe turning on pull-ups would
help with that?

external_mem.c

@@ -336,12 +336,69 @@ void ExternalMem_WriteByteToChips(uint32_t address, uint32_t data, uint8_t chips
 	ExternalMem_WaitCompletion(chipsMask);
 }
 
-void ExternalMem_Write(uint32_t startAddress, uint32_t *buf, uint32_t len, uint8_t chipsMask)
+uint8_t ExternalMem_Write(uint32_t startAddress, uint32_t *buf, uint32_t len, uint8_t chipsMask, bool doVerify)
 {
+	// Use a mask so we don't worry about chips we don't want to talk with
+	uint32_t mask = ExternalMem_MaskForChips(chipsMask);
+
 	while (len--)
 	{
-		ExternalMem_WriteByteToChips(startAddress++, *buf++, chipsMask);
+		ExternalMem_WriteByteToChips(startAddress, *buf, chipsMask);
+		if (doVerify)
+		{
+			#define VERIFY_EXTRA_READ_TRIES	2
+
+			// Read back the word we just wrote to make sure it's OK...
+			uint32_t readback = ExternalMem_ReadCycle(startAddress) & mask;
+			if (readback != (*buf & mask))
+			{
+				// We found a failure, but don't despair yet. Let's try reading
+				// two more times in case it a fluke of the data toggle polling
+				// algorithm.
+				bool secondFailureFound = false;
+				int try = 0;
+
+				while ((try < VERIFY_EXTRA_READ_TRIES) && !secondFailureFound)
+				{
+					try++;
+					readback = ExternalMem_ReadCycle(startAddress) & mask;
+					if (readback != (*buf & mask))
+					{
+						secondFailureFound = true;
+					}
+				}
+
+				// If we re-read it a few times and it failed again, the write
+				// failed. Otherwise, it was probably just the data toggle
+				// polling algorithm giving us fits.
+				if (secondFailureFound)
+				{
+					uint8_t failMask = 0;
+					// Figure out the mask of chip(s) acting up
+					int x;
+					for (x = 0; x < NUM_CHIPS; x++)
+					{
+						// Is this a chip we're working with?
+						if (chipsMask & (1 << x))
+						{
+							if ((readback & (0xFFUL << (8*x))) != (*buf & (0xFFUL << (8*x))))
+							{
+								// Save the failMask in reverse order
+								// (so bit 0 refers to IC1 rather than IC4)
+								failMask |= (1 << ((NUM_CHIPS - 1) - x));
+							}
+						}
+					}
+					return failMask;
+				}
+			}
+		}
+
+		startAddress++;
+		buf++;
 	}
+
+	return 0;
 }
 
 void ExternalMem_SetChipType(ChipType type)

external_mem.h

@@ -101,7 +101,9 @@ void ExternalMem_WriteByteToChips(uint32_t address, uint32_t data, uint8_t chips
 // Writes a buffer to the requested chips simultaneously
 // (each uint32_t contains an 8-bit portion for each chip,
 // which is masked away if the chip is not requested)
-void ExternalMem_Write(uint32_t startAddress, uint32_t *buf, uint32_t len, uint8_t chipsMask);
+// returns a mask representing the chips acting up (if requested with doVerify)
+// or 0 on success (or if verification was not requested)
+uint8_t ExternalMem_Write(uint32_t startAddress, uint32_t *buf, uint32_t len, uint8_t chipsMask, bool doVerify);
 
 // Tells which flash command protocol to use
 void ExternalMem_SetChipType(ChipType type);

programmer_protocol.h

@@ -43,7 +43,9 @@ typedef enum ProgrammerCommand
 	EnterProgrammer,
 	BootloaderEraseAndWriteProgram,
     SetSIMMTypePLCC32_2MB,
-    SetSIMMTypeLarger
+    SetSIMMTypeLarger,
+    SetVerifyWhileWriting,
+    SetNoVerifyWhileWriting
 } ProgrammerCommand;
 
 // After a command is sent, the programmer will always respond with
@@ -115,6 +117,11 @@ typedef enum ComputerReadReply
 // this one, and then the computer can send a 1024-byte chunk of data.
 // The programmer will reply with ProgrammerWriteOK, and then the cycle can
 // continue (the computer sends another request in this enum)
+//
+// If the programmer was asked to verify while writing and a verification error
+// occurs, it will respond with ProgrammerWriteVerificationError ORed with a bit
+// mask of chips that are acting up (so it could be 0x81 if IC1 is acting up,
+// for example)
 typedef enum ComputerWriteRequest
 {
 	ComputerWriteMore = 0,
@@ -126,7 +133,8 @@ typedef enum ProgrammerWriteReply
 {
 	ProgrammerWriteOK = 0,
 	ProgrammerWriteError,
-	ProgrammerWriteConfirmCancel
+	ProgrammerWriteConfirmCancel,
+	ProgrammerWriteVerificationError = 0x80 /* high bit signifies verify error, low bits signify which chips are bad */
 } ProgrammerWriteReply;
 
 // -------------------------  BOOTLOADER STATE PROTOCOL  -------------------------

usb_serial/usb_serial.c

@@ -29,6 +29,7 @@
 #include "../tests/simm_electrical_test.h"
 #include "../programmer_protocol.h"
 #include "../led.h"
+#include <stdbool.h>
 
 #define MAX_CHIP_SIZE				(2UL * 1024UL * 1024UL)
 #define READ_CHUNK_SIZE_BYTES		1024UL
@@ -64,6 +65,7 @@ static uint32_t readLength;
 static uint8_t readLengthByteIndex;
 static int16_t writePosInChunk = -1;
 static uint16_t curWriteIndex = 0;
+static bool verifyDuringWrite = false;
 
 // Private functions
 void USBSerial_HandleWaitingForCommandByte(uint8_t byte);
@@ -217,6 +219,14 @@ void USBSerial_HandleWaitingForCommandByte(uint8_t byte)
 		ExternalMem_SetChipType(ChipType8Bit16BitData_16MBitSize);
 		SendByte(CommandReplyOK);
 		break;
+	case SetVerifyWhileWriting:
+		verifyDuringWrite = true;
+		SendByte(CommandReplyOK);
+		break;
+	case SetNoVerifyWhileWriting:
+		verifyDuringWrite = false;
+		SendByte(CommandReplyOK);
+		break;
 	// We don't know what this command is, so reply that it was invalid.
 	default:
 		SendByte(CommandReplyInvalid);
@@ -373,12 +383,25 @@ void USBSerial_HandleWritingChipsByte(uint8_t byte)
 		{
 			// We filled up the chunk, write it out and confirm it, then wait
 			// for the next command from the computer!
-			ExternalMem_Write(curWriteIndex * (WRITE_CHUNK_SIZE_BYTES/4),
-					chunks.writeChunks, WRITE_CHUNK_SIZE_BYTES/4, ALL_CHIPS);
-			SendByte(ProgrammerWriteOK);
-			curWriteIndex++;
-			writePosInChunk = -1;
-			LED_Toggle();
+			uint8_t writeResult = ExternalMem_Write(curWriteIndex * (WRITE_CHUNK_SIZE_BYTES/4),
+					chunks.writeChunks, WRITE_CHUNK_SIZE_BYTES/4, ALL_CHIPS, verifyDuringWrite);
+
+			// But if we asked to verify, make sure it came out OK.
+			if (verifyDuringWrite && (writeResult != 0))
+			{
+				// Uh oh -- verification failure.
+				LED_Off();
+				// Send the fail bit along with a mask of failed chips.
+				SendByte(ProgrammerWriteVerificationError | writeResult);
+				curCommandState = WaitingForCommand;
+			}
+			else
+			{
+				SendByte(ProgrammerWriteOK);
+				curWriteIndex++;
+				writePosInChunk = -1;
+				LED_Toggle();
+			}
 		}
 	}
 }