diff --git a/flight/Bootloaders/OpenPilot/Makefile b/flight/Bootloaders/OpenPilot/Makefile
index 264ae9d38..24d0309b8 100644
--- a/flight/Bootloaders/OpenPilot/Makefile
+++ b/flight/Bootloaders/OpenPilot/Makefile
@@ -51,7 +51,7 @@ USE_THUMB_MODE = YES
 # - BOARD just passed as define (optional)
 MCU      = cortex-m3
 CHIP     = STM32F103RET
-MODEL    = HD_BL
+MODEL    = HD
 BOARD    = STM3210E_OP
 
 # Directory for output files (lst, obj, dep, elf, sym, map, hex, bin etc.)
@@ -83,7 +83,9 @@ DOXYGENDIR = .../Doc/Doxygen
 # use file-extension c for "c-only"-files
 
 ## OPENPILOT Bootloader:
-SRC = $(OPBLSYSTEM)/openpilot_bl.c
+SRC =  $(OPBLSYSTEM)/openpilot_bl.c
+SRC += $(OPBLSYSTEM)/bootloader.c
+SRC += $(OPBLSYSTEM)/ymodem.c
 
 ## PIOS Hardware (STM32F10x)
 SRC += $(PIOSSTM32F10X)/pios_sys.c
@@ -91,8 +93,8 @@ SRC += $(PIOSSTM32F10X)/pios_led.c
 SRC += $(PIOSSTM32F10X)/pios_usart.c
 SRC += $(PIOSSTM32F10X)/pios_delay.c
 SRC += $(PIOSSTM32F10X)/pios_irq.c
-#SRC += $(PIOSSTM32F10X)/pios_usb.c
-#SRC += $(PIOSSTM32F10X)/pios_usb_hid.c
+SRC += $(PIOSSTM32F10X)/pios_usb.c
+SRC += $(PIOSSTM32F10X)/pios_usb_hid.c
 
 ## PIOS Hardware (Common)
 SRC += $(PIOSCOMMON)/pios_com.c
@@ -105,16 +107,18 @@ SRC += $(CMSISDIR)/system_stm32f10x.c
 ## Used parts of the STM-Library
 SRC += $(STMSPDSRCDIR)/stm32f10x_gpio.c
 SRC += $(STMSPDSRCDIR)/stm32f10x_rcc.c
+SRC += $(STMSPDSRCDIR)/stm32f10x_wwdg.c
 SRC += $(STMSPDSRCDIR)/stm32f10x_tim.c
+SRC += $(STMSPDSRCDIR)/stm32f10x_flash.c
 SRC += $(STMSPDSRCDIR)/stm32f10x_usart.c
 SRC += $(STMSPDSRCDIR)/misc.c
 
 ## STM32 USB Library
-#SRC += $(STMUSBSRCDIR)/usb_core.c
-#SRC += $(STMUSBSRCDIR)/usb_init.c
-#SRC += $(STMUSBSRCDIR)/usb_int.c
-#SRC += $(STMUSBSRCDIR)/usb_mem.c
-3SRC += $(STMUSBSRCDIR)/usb_regs.c
+SRC += $(STMUSBSRCDIR)/usb_core.c
+SRC += $(STMUSBSRCDIR)/usb_init.c
+SRC += $(STMUSBSRCDIR)/usb_int.c
+SRC += $(STMUSBSRCDIR)/usb_mem.c
+SRC += $(STMUSBSRCDIR)/usb_regs.c
 
 # List C source files here which must be compiled in ARM-Mode (no -mthumb).
 # use file-extension c for "c-only"-files
diff --git a/flight/Bootloaders/OpenPilot/bootloader.c b/flight/Bootloaders/OpenPilot/bootloader.c
new file mode 100644
index 000000000..a74712ffa
--- /dev/null
+++ b/flight/Bootloaders/OpenPilot/bootloader.c
@@ -0,0 +1,205 @@
+/**
+ ******************************************************************************
+ *
+ * @file       bootloader.h
+ * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
+ * @brief      Bootloader functions header
+ * @see        The GNU Public License (GPL) Version 3
+ *
+ *****************************************************************************/
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+/* Includes */
+#include "openpilot_bl.h"
+
+/* Local Functions */
+static void Serial_PutString(uint8_t *s);
+static void FLASH_DisableWriteProtectionPages(void);
+static void SerialDownload(void);
+
+/* Global Variables */
+extern uint32_t FlashDestination;
+extern uint8_t file_name[FILE_NAME_LENGTH];
+
+/* Local variables */
+uint32_t BlockNbr = 0, UserMemoryMask = 0;
+bool FlashProtection = FALSE;
+uint8_t tab_1024[1024] = { 0 };
+
+/**
+ * Main bootloader function
+ */
+void StartBootloader(void)
+{
+	uint8_t key = 0;
+
+	/* Get the number of block (4 or 2 pages) from where the user program will be loaded */
+	BlockNbr = (FlashDestination - 0x08000000) >> 12;
+
+	/* Compute the mask to test if the Flash memory, where the user program will be loaded, is write protected */
+	if(BlockNbr < 62) {
+		UserMemoryMask = ((uint32_t) ~((1 << BlockNbr) - 1));
+	} else {
+		UserMemoryMask = ((uint32_t) 0x80000000);
+	}
+
+	/* Test if any page of Flash memory where program user will be loaded is write protected */
+	if((FLASH_GetWriteProtectionOptionByte() & UserMemoryMask) != UserMemoryMask) {
+		FlashProtection = TRUE;
+		SerialPutString("  Download Image To the STM32F10x Internal Flash ------- 1\r\n");
+		SerialPutString("  Execute The New Program ------------------------------ 2\r\n");
+		SerialPutString("  Disable the write protection ------------------------- 3\r\n");
+	} else {
+		FlashProtection = FALSE;
+		SerialPutString("  Download Image To the STM32F10x Internal Flash ------- 1\r\n");
+		SerialPutString("  Execute The New Program ------------------------------ 2\r\n");
+	}
+
+	/* Loop through 1mS check for specified time */
+	for(int32_t i = 0; i < OPBL_MAGIC_TIMEOUT; i++) {
+		uint16_t start = PIOS_DELAY_TIMER->CNT;
+
+		/* Check for magic character for 1mS */
+		while((volatile uint16_t)(PIOS_DELAY_TIMER->CNT - start) <= 1000) {
+			/* Check to see if there is anything on the receiving buffer */
+			if(PIOS_COM_ReceiveBufferUsed(OPBL_COM_PORT) > 0) {
+				key = PIOS_COM_ReceiveBuffer(OPBL_COM_PORT);
+				if(key == 0x31) {
+					/* Download user application in the Flash */
+					SerialDownload();
+					return;
+				} else if ((key == 0x33) && (FlashProtection == TRUE)) {
+					/* Disable the write protection of desired pages */
+					FLASH_DisableWriteProtectionPages();
+				}
+			}
+		}
+	}
+
+	return;
+}
+
+/**
+ * Calculate the number of pages
+ * \param[in] Size The image size
+ * \return The number of pages
+ */
+uint32_t FLASH_PagesMask(__IO uint32_t Size)
+{
+	uint32_t pagenumber = 0x0;
+	uint32_t size = Size;
+
+	if((size % PAGE_SIZE) != 0) {
+		pagenumber = (size / PAGE_SIZE) + 1;
+	} else {
+		pagenumber = size / PAGE_SIZE;
+	}
+	return pagenumber;
+
+}
+
+/**
+ * Print a string on the HyperTerminal
+ * \param[in] s The string to be printed
+ */
+static void Serial_PutString(uint8_t *s)
+{
+	while(*s != '\0') {
+		PIOS_COM_SendChar(OPBL_COM_PORT, *s);
+		s++;
+	}
+}
+
+/**
+ * Disable the write protection of desired pages
+ */
+static void FLASH_DisableWriteProtectionPages(void)
+{
+	uint32_t useroptionbyte = 0, WRPR = 0;
+	uint16_t var1 = OB_IWDG_SW, var2 = OB_STOP_NoRST, var3 = OB_STDBY_NoRST;
+	FLASH_Status status = FLASH_BUSY;
+
+	WRPR = FLASH_GetWriteProtectionOptionByte();
+
+	/* Test if user memory is write protected */
+	if((WRPR & UserMemoryMask) != UserMemoryMask) {
+		useroptionbyte = FLASH_GetUserOptionByte();
+
+		UserMemoryMask |= WRPR;
+
+		status = FLASH_EraseOptionBytes();
+
+		if(UserMemoryMask != 0xFFFFFFFF) {
+			status = FLASH_EnableWriteProtection(
+					(uint32_t) ~UserMemoryMask);
+		}
+
+		/* Test if user Option Bytes are programmed */
+		if((useroptionbyte & 0x07) != 0x07) { /* Restore user Option Bytes */
+			if((useroptionbyte & 0x01) == 0x0) {
+				var1 = OB_IWDG_HW;
+			}
+			if((useroptionbyte & 0x02) == 0x0) {
+				var2 = OB_STOP_RST;
+			}
+			if((useroptionbyte & 0x04) == 0x0) {
+				var3 = OB_STDBY_RST;
+			}
+
+			FLASH_UserOptionByteConfig(var1, var2, var3);
+		}
+
+		if(status == FLASH_COMPLETE) {
+			SerialPutString("Write Protection disabled...\r\n");
+
+			SerialPutString("...and a System Reset will be generated to re-load the new option bytes\r\n");
+
+			/* Enable WWDG clock */
+			RCC_APB1PeriphClockCmd(RCC_APB1Periph_WWDG, ENABLE);
+
+			/* Generate a system Reset to re-load the new option bytes: enable WWDG and set
+			 counter value to 0x4F, as T6 bit is cleared this will generate a WWDG reset */
+			WWDG_Enable(0x4F);
+		} else {
+			SerialPutString("Error: Flash write unprotection failed...\r\n");
+		}
+	} else {
+		SerialPutString("Flash memory not write protected\r\n");
+	}
+}
+
+/**
+ * Download and program the binary file
+ */
+static void SerialDownload(void)
+{
+	int32_t Size = 0;
+
+	SerialPutString("Waiting for the file to be sent ... (press 'a' to abort)\n\r");
+	Size = Ymodem_Receive(&tab_1024[0]);
+	if(Size > 0) {
+		SerialPutString("\n\n\r Programming Completed Successfully!\n\r--------------------------------\r\n Name: ");
+	} else if(Size == -1) {
+		SerialPutString("\n\n\rThe image size is higher than the allowed space memory!\n\r");
+	} else if(Size == -2) {
+		SerialPutString("\n\n\rVerification failed!\n\r");
+	} else if(Size == -3) {
+		SerialPutString("\r\n\nAborted by user.\n\r");
+	} else {
+		SerialPutString("\n\rFailed to receive the file!\n\r");
+	}
+}
diff --git a/flight/Bootloaders/OpenPilot/inc/bootloader.h b/flight/Bootloaders/OpenPilot/inc/bootloader.h
new file mode 100644
index 000000000..4fa620ef9
--- /dev/null
+++ b/flight/Bootloaders/OpenPilot/inc/bootloader.h
@@ -0,0 +1,45 @@
+/**
+ ******************************************************************************
+ *
+ * @file       bootloader.h
+ * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
+ * @brief      Bootloader functions header
+ * @see        The GNU Public License (GPL) Version 3
+ *
+ *****************************************************************************/
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef BOOTLOADER_H
+#define BOOTLOADER_H
+
+/* Global Types */
+typedef  void (*pFunction)(void);
+
+/* Global Defines */
+#define CMD_STRING_SIZE			128
+#define ApplicationAddress		0x8008000
+#define PAGE_SIZE			(0x800)
+#define FLASH_SIZE			(0x80000)	/* 512K */
+
+/* Global macros */
+#define SerialPutString(x)		Serial_PutString((uint8_t*)(x))
+
+/* Public Functions */
+extern void StartBootloader(void);
+extern uint32_t FLASH_PagesMask(volatile uint32_t Size);
+
+#endif  /* BOOTLOADER_H */
diff --git a/flight/Bootloaders/OpenPilot/inc/openpilot_bl.h b/flight/Bootloaders/OpenPilot/inc/openpilot_bl.h
index 694b3e80a..a8fef5a00 100644
--- a/flight/Bootloaders/OpenPilot/inc/openpilot_bl.h
+++ b/flight/Bootloaders/OpenPilot/inc/openpilot_bl.h
@@ -27,8 +27,12 @@
 #ifndef OPENPILOT_BL_H
 #define OPENPILOT_BL_H
 
+#define OPBL_MAGIC_TIMEOUT		2000
+#define OPBL_COM_PORT			COM_DEBUG_USART
 
 /* PIOS Includes */
 #include <pios.h>
+#include "bootloader.h"
+#include "ymodem.h"
 
 #endif /* OPENPILOT_BL_H */
diff --git a/flight/Bootloaders/OpenPilot/inc/pios_board.h b/flight/Bootloaders/OpenPilot/inc/pios_board.h
index 983084e89..98e5530b1 100644
--- a/flight/Bootloaders/OpenPilot/inc/pios_board.h
+++ b/flight/Bootloaders/OpenPilot/inc/pios_board.h
@@ -27,6 +27,7 @@
 #ifndef PIOS_BOARD_H
 #define PIOS_BOARD_H
 
+
 //------------------------
 // PIOS_LED
 //------------------------
@@ -54,7 +55,7 @@
 #define PIOS_USART1_IRQHANDLER_FUNC		void USART2_IRQHandler(void)
 #define PIOS_USART1_CLK_FUNC			RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE)
 #define PIOS_USART1_NVIC_PRIO			PIOS_IRQ_PRIO_HIGHEST
-#define PIOS_USART1_BAUDRATE			57600
+#define PIOS_USART1_BAUDRATE			115200
 
 //-------------------------
 // PIOS_USART2 (GPS)
@@ -90,8 +91,8 @@
 // PIOS_USART
 //-------------------------
 #define PIOS_USART_NUM				1
-#define PIOS_USART_RX_BUFFER_SIZE		1024
-#define PIOS_USART_TX_BUFFER_SIZE		256
+#define PIOS_USART_RX_BUFFER_SIZE		128
+#define PIOS_USART_TX_BUFFER_SIZE		128
 #define PIOS_COM_DEBUG_PORT			USART_1
 
 //-------------------------
@@ -101,10 +102,11 @@
 #define PIOS_DELAY_TIMER_RCC_FUNC		RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE)
 
 //-------------------------
-// Master Clock
+// System Settings
 //-------------------------
 #define PIOS_MASTER_CLOCK			72000000
 #define PIOS_PERIPHERAL_CLOCK			(PIOS_MASTER_CLOCK / 2)
+#define PIOS_NVIC_VECTTAB_FLASH			((uint32_t)0x08000000)
 
 //-------------------------
 // Interrupt Priorities
diff --git a/flight/Bootloaders/OpenPilot/inc/pios_config.h b/flight/Bootloaders/OpenPilot/inc/pios_config.h
index 965bb274a..0e0e9ddd7 100644
--- a/flight/Bootloaders/OpenPilot/inc/pios_config.h
+++ b/flight/Bootloaders/OpenPilot/inc/pios_config.h
@@ -41,8 +41,8 @@
 #define PIOS_INCLUDE_SYS
 #define PIOS_INCLUDE_USART
 //#define PIOS_INCLUDE_USB_COM
-//#define PIOS_INCLUDE_USB_HID
-//#define PIOS_INCLUDE_USB
+#define PIOS_INCLUDE_USB_HID
+#define PIOS_INCLUDE_USB
 //#define PIOS_INCLUDE_BMP085
 #define PIOS_INCLUDE_COM
 //#define PIOS_INCLUDE_SDCARD
diff --git a/flight/Bootloaders/OpenPilot/inc/ymodem.h b/flight/Bootloaders/OpenPilot/inc/ymodem.h
new file mode 100644
index 000000000..fd0053036
--- /dev/null
+++ b/flight/Bootloaders/OpenPilot/inc/ymodem.h
@@ -0,0 +1,73 @@
+/**
+ ******************************************************************************
+ *
+ * @file       ymodem.c
+ * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
+ * @brief      YModem functions header
+ * @see        The GNU Public License (GPL) Version 3
+ *
+ *****************************************************************************/
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef YMODEM_H
+#define YMODEM_H
+
+/* Global Defines */
+#define PACKET_SEQNO_INDEX      (1)
+#define PACKET_SEQNO_COMP_INDEX (2)
+
+#define PACKET_HEADER           (3)
+#define PACKET_TRAILER          (2)
+#define PACKET_OVERHEAD         (PACKET_HEADER + PACKET_TRAILER)
+#define PACKET_SIZE             (128)
+#define PACKET_1K_SIZE          (1024)
+
+#define FILE_NAME_LENGTH        (256)
+#define FILE_SIZE_LENGTH        (16)
+
+#define SOH                     (0x01)  /* start of 128-byte data packet */
+#define STX                     (0x02)  /* start of 1024-byte data packet */
+#define EOT                     (0x04)  /* end of transmission */
+#define ACK                     (0x06)  /* acknowledge */
+#define NAK                     (0x15)  /* negative acknowledge */
+#define CA                      (0x18)  /* two of these in succession aborts transfer */
+#define CRC16                   (0x43)  /* 'C' == 0x43, request 16-bit CRC */
+
+#define ABORT1                  (0x41)  /* 'A' == 0x41, abort by user */
+#define ABORT2                  (0x61)  /* 'a' == 0x61, abort by user */
+
+#define NAK_TIMEOUT             (0x100000)
+#define MAX_ERRORS              (5)
+
+/* Global Macros */
+#define IS_AF(c)  ((c >= 'A') && (c <= 'F'))
+#define IS_af(c)  ((c >= 'a') && (c <= 'f'))
+#define IS_09(c)  ((c >= '0') && (c <= '9'))
+#define ISVALIDHEX(c)  IS_AF(c) || IS_af(c) || IS_09(c)
+#define ISVALIDDEC(c)  IS_09(c)
+#define CONVERTDEC(c)  (c - '0')
+
+#define CONVERTHEX_alpha(c)  (IS_AF(c) ? (c - 'A'+10) : (c - 'a'+10))
+#define CONVERTHEX(c)   (IS_09(c) ? (c - '0') : CONVERTHEX_alpha(c))
+
+/* Global Variables */
+extern uint8_t tab_1024[1024];
+
+/* Public Functions */
+extern int32_t Ymodem_Receive(uint8_t *buf);
+
+#endif  /* YMODEM_H */
diff --git a/flight/Bootloaders/OpenPilot/openpilot_bl.c b/flight/Bootloaders/OpenPilot/openpilot_bl.c
index 1face1d6d..e6458e8a6 100644
--- a/flight/Bootloaders/OpenPilot/openpilot_bl.c
+++ b/flight/Bootloaders/OpenPilot/openpilot_bl.c
@@ -28,6 +28,8 @@
 #include "openpilot_bl.h"
 
 /* Global Variables */
+static pFunction Jump_To_Application;
+static uint32_t JumpAddress;
 
 /* Local Variables */
 
@@ -41,19 +43,47 @@ int main()
 	/* Brings up System using CMSIS functions, enables the LEDs. */
 	PIOS_SYS_Init();
 
-	/* Delay system */
-	PIOS_DELAY_Init();
+	/* Only go into bootloader when the USB cable is connected */
+	if(PIOS_USB_CableConnected()) {
+		/* Delay system */
+		PIOS_DELAY_Init();
 
-	/* Initialise LED's */
-	PIOS_LED_Init();
+		/* Initialise the USB system */
+		PIOS_USB_Init(0);
 
-	/* Loop for ever */
+		/* Initialise COM Ports */
+		PIOS_COM_Init();
+
+		/* Initialise LED's */
+		PIOS_LED_Init();
+		PIOS_LED_Off(LED1);
+		PIOS_LED_Off(LED2);
+
+		/* Flash unlock */
+		FLASH_Unlock();
+
+		/* Execute the IAP driver in order to re-program the Flash */
+		StartBootloader();
+	}
+
+	/* Test if user code is programmed starting from address "ApplicationAddress" */
+	if(((*(volatile uint32_t*) ApplicationAddress) & 0x2FFE0000) == 0x20000000) {
+		/* Jump to user application */
+		JumpAddress = *(volatile uint32_t*) (ApplicationAddress + 4);
+		Jump_To_Application = (pFunction) JumpAddress;
+
+		/* Initialise user application's Stack Pointer */
+		__set_MSP(*(volatile uint32_t*) ApplicationAddress);
+		Jump_To_Application();
+	}
+
+	/* Loop for ever if no application code is not programmed */
 	PIOS_LED_Off(LED1);
 	PIOS_LED_Off(LED2);
 	for(;;) {
 		PIOS_LED_Toggle(LED1);
 		PIOS_LED_Toggle(LED2);
-		PIOS_DELAY_WaitmS(200);
+		PIOS_DELAY_WaitmS(50);
 	}
 
 	return 0;
diff --git a/flight/Bootloaders/OpenPilot/ymodem.c b/flight/Bootloaders/OpenPilot/ymodem.c
new file mode 100644
index 000000000..a5680ef76
--- /dev/null
+++ b/flight/Bootloaders/OpenPilot/ymodem.c
@@ -0,0 +1,325 @@
+/**
+ ******************************************************************************
+ *
+ * @file       ymodem.c
+ * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
+ * @brief      YModem functions
+ * @see        The GNU Public License (GPL) Version 3
+ *
+ *****************************************************************************/
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+/* Includes */
+#include "openpilot_bl.h"
+
+/* Local functions */
+static int32_t Receive_Byte(uint8_t *c, uint32_t timeout);
+static uint32_t Send_Byte(uint8_t c);
+static int32_t Receive_Packet(uint8_t *data, int32_t *length, uint32_t timeout);
+static uint32_t Str2Int(uint8_t *inputstr, int32_t *intnum);
+
+/* Global variables */
+uint32_t FlashDestination = ApplicationAddress; /* Flash user program offset */
+uint8_t tab_1024[1024];
+
+/* Local variables */
+static uint8_t file_name[FILE_NAME_LENGTH];
+static uint16_t PageSize = PAGE_SIZE;
+static uint32_t EraseCounter = 0x0;
+static uint32_t NbrOfPage = 0;
+static FLASH_Status FLASHStatus = FLASH_COMPLETE;
+static uint32_t RamSource;
+
+
+/**
+ * Receive a file using the ymodem protocol
+ * \param[in]  buf Address of the first byte
+ * \return The size of the file
+ */
+int32_t Ymodem_Receive(uint8_t *buf)
+{
+	uint8_t packet_data[PACKET_1K_SIZE + PACKET_OVERHEAD], file_size[FILE_SIZE_LENGTH], *file_ptr, *buf_ptr;
+	int32_t i, j, packet_length, session_done, file_done, packets_received, errors, session_begin, size = 0;
+
+	/* Initialise FlashDestination variable */
+	FlashDestination = ApplicationAddress;
+
+	for(session_done = 0, errors = 0, session_begin = 0;;) {
+		for(packets_received = 0, file_done = 0, buf_ptr = buf;;) {
+			switch(Receive_Packet(packet_data, &packet_length,
+					NAK_TIMEOUT)) {
+				case 0:
+					errors = 0;
+					switch(packet_length) {
+						/* Abort by sender */
+						case -1:
+							Send_Byte(ACK);
+							return 0;
+							/* End of transmission */
+						case 0:
+							Send_Byte(ACK);
+							file_done = 1;
+							break;
+							/* Normal packet */
+						default:
+							if((packet_data[PACKET_SEQNO_INDEX] & 0xff) != (packets_received & 0xff)) {
+								Send_Byte(NAK);
+							} else {
+								if(packets_received == 0) {/* Filename packet */
+									if(packet_data[PACKET_HEADER] != 0) {/* Filename packet has valid data */
+										for(i = 0, file_ptr = packet_data + PACKET_HEADER; (*file_ptr != 0) && (i < FILE_NAME_LENGTH);) {
+											file_name[i++] = *file_ptr++;
+										}
+										file_name[i++] = '\0';
+										for(i = 0, file_ptr++; (*file_ptr != ' ') & (i < FILE_SIZE_LENGTH);) {
+											file_size[i++] = *file_ptr++;
+										}
+										file_size[i++] = '\0';
+										Str2Int(file_size, &size);
+										/* Test the size of the image to be sent */
+										/* Image size is greater than Flash size */
+										if(size > (FLASH_SIZE - 1)) {
+											/* End session */
+											Send_Byte(CA);
+											Send_Byte(CA);
+											return -1;
+										}
+										/* Erase the needed pages where the user application will be loaded */
+										/* Define the number of page to be erased */
+										NbrOfPage = FLASH_PagesMask(size);
+										/* Erase the FLASH pages */
+										for(EraseCounter = 0; (EraseCounter < NbrOfPage) && (FLASHStatus == FLASH_COMPLETE); EraseCounter++) {
+											FLASHStatus = FLASH_ErasePage(FlashDestination + (PageSize * EraseCounter));
+										}
+										Send_Byte(ACK);
+										Send_Byte(CRC16);
+									}
+									/* Filename packet is empty, end session */
+									else {
+										Send_Byte(ACK);
+										file_done = 1;
+										session_done = 1;
+										break;
+									}
+								}
+								/* Data packet */
+								else {
+									memcpy(buf_ptr, packet_data + PACKET_HEADER, packet_length);
+									RamSource = (uint32_t) buf;
+									for(j = 0; (j < packet_length) && (FlashDestination < ApplicationAddress + size); j += 4) {
+										/* Program the data received into STM32F10x Flash */
+										FLASH_ProgramWord(FlashDestination, *(uint32_t*) RamSource);
+										if(*(uint32_t*) FlashDestination != *(uint32_t*) RamSource) {
+											/* End session */
+											Send_Byte(CA);
+											Send_Byte(CA);
+											return -2;
+										}
+										FlashDestination += 4;
+										RamSource += 4;
+									}
+									Send_Byte(ACK);
+								}
+								packets_received++;
+								session_begin = 1;
+							}
+					}
+					break;
+				case 1:
+					Send_Byte(CA);
+					Send_Byte(CA);
+					return -3;
+				default:
+					if(session_begin > 0) {
+						errors++;
+					}
+					if(errors > MAX_ERRORS) {
+						Send_Byte(CA);
+						Send_Byte(CA);
+						return 0;
+					}
+					Send_Byte(CRC16);
+					break;
+			}
+			if(file_done != 0) {
+				break;
+			}
+		}
+		if(session_done != 0) {
+			break;
+		}
+	}
+	return (int32_t) size;
+}
+
+/**
+ * Receive byte from sender
+ * \param[in] c Character
+ * \param[in] timeout Timeout
+ * \return 0 Byte received
+ * \return -1 Timeout
+ */
+static int32_t Receive_Byte(uint8_t *c, uint32_t timeout)
+{
+	while(timeout-- > 0) {
+		if(PIOS_COM_ReceiveBufferUsed(OPBL_COM_PORT) > 0) {
+			*c = PIOS_COM_ReceiveBuffer(OPBL_COM_PORT);
+			return 0;
+		}
+	}
+	return -1;
+}
+
+/**
+ * Send a byte
+ * \param[in] c Character
+ * \return 0 Byte sent
+ */
+static uint32_t Send_Byte(uint8_t c)
+{
+	PIOS_COM_SendChar(OPBL_COM_PORT, c);
+	return 0;
+}
+
+/**
+ * Receive a packet from sender
+ * \param[in] data
+ * \param[in] length
+ * \param[in] timeout
+ *     0 end of transmission
+ *    -1 abort by sender
+ *    >0 packet length
+ * \return 0 normally return
+ * \return -1 timeout or packet error
+ * \return 1 abort by user
+ */
+static int32_t Receive_Packet(uint8_t *data, int32_t *length, uint32_t timeout)
+{
+	uint16_t i, packet_size;
+	uint8_t c;
+	*length = 0;
+	if(Receive_Byte(&c, timeout) != 0) {
+		return -1;
+	}
+	switch(c) {
+		case SOH:
+			packet_size = PACKET_SIZE;
+			break;
+		case STX:
+			packet_size = PACKET_1K_SIZE;
+			break;
+		case EOT:
+			return 0;
+		case CA:
+			if((Receive_Byte(&c, timeout) == 0) && (c == CA)) {
+				*length = -1;
+				return 0;
+			} else {
+				return -1;
+			}
+		case ABORT1:
+		case ABORT2:
+			return 1;
+		default:
+			return -1;
+	}
+	*data = c;
+	for(i = 1; i < (packet_size + PACKET_OVERHEAD); i++) {
+		if(Receive_Byte(data + i, timeout) != 0) {
+			return -1;
+		}
+	}
+	if(data[PACKET_SEQNO_INDEX] != ((data[PACKET_SEQNO_COMP_INDEX] ^ 0xff)
+			& 0xff)) {
+		return -1;
+	}
+	*length = packet_size;
+	return 0;
+}
+
+/**
+ * Convert a string to an integer
+ * \param[in] inputstr The string to be converted
+ * \param[in] intnum The intger value
+ * \return 1 Correct
+ * \return 0 Error
+ */
+static uint32_t Str2Int(uint8_t *inputstr, int32_t *intnum)
+{
+	uint32_t i = 0, res = 0;
+	uint32_t val = 0;
+
+	if(inputstr[0] == '0' && (inputstr[1] == 'x' || inputstr[1] == 'X')) {
+		if(inputstr[2] == '\0') {
+			return 0;
+		}
+		for(i = 2; i < 11; i++) {
+			if(inputstr[i] == '\0') {
+				*intnum = val;
+				/* return 1; */
+				res = 1;
+				break;
+			}
+			if(ISVALIDHEX(inputstr[i])) {
+				val = (val << 4) + CONVERTHEX(inputstr[i]);
+			} else {
+				/* return 0, Invalid input */
+				res = 0;
+				break;
+			}
+		}
+		/* over 8 digit hex --invalid */
+		if(i >= 11) {
+			res = 0;
+		}
+	} else /* max 10-digit decimal input */
+	{
+		for(i = 0; i < 11; i++) {
+			if(inputstr[i] == '\0') {
+				*intnum = val;
+				/* return 1 */
+				res = 1;
+				break;
+			} else if((inputstr[i] == 'k' || inputstr[i] == 'K')
+					&& (i > 0)) {
+				val = val << 10;
+				*intnum = val;
+				res = 1;
+				break;
+			} else if((inputstr[i] == 'm' || inputstr[i] == 'M')
+					&& (i > 0)) {
+				val = val << 20;
+				*intnum = val;
+				res = 1;
+				break;
+			} else if(ISVALIDDEC(inputstr[i])) {
+				val = val * 10 + CONVERTDEC(inputstr[i]);
+			} else {
+				/* return 0, Invalid input */
+				res = 0;
+				break;
+			}
+		}
+		/* Over 10 digit decimal --invalid */
+		if(i >= 11) {
+			res = 0;
+		}
+	}
+
+	return res;
+}
+