Use the PDI REPEAT instruction in the PDI programmer code to reduce protocol overhead and greatly improve transfer throughput. Switch bit-bang USART in the AVRISP project to Timer 1, so that Timer 0 can be used for hardware timeouts while waiting for the NVM bus or controller to become ready.

Projects/AVRISP/Lib/PDIProtocol.c

@@ -114,7 +114,7 @@ static void PDIProtocol_EnterXPROGMode(void)
 	  PDITarget_SendByte(PDI_NVMENABLE_KEY[i - 1]);
 
 	/* Wait until the NVM bus becomes active */
-	bool NVMBusEnabled = NVMTarget_WaitWhileNVMBusBusy();
+	bool NVMBusEnabled = PDITarget_WaitWhileNVMBusBusy();
 	
 	Endpoint_Write_Byte(CMD_XPROG);
 	Endpoint_Write_Byte(XPRG_CMD_ENTER_PROGMODE);