ST AN2078 Application note

AN2078

Application note

STR7 In-Application Programming using UART

Introduction

An important requirement for most Flash-based systems is the ability to update firmware while the system is installed in the end product. This is referred to as In-Application Programming (IAP).

STR7xx MCUs have the capability of running user-specific firmware to perform In Application Programming of the MCU embedded Flash memory. This feature allows the use of any type of communication protocol for the reprogramming process (for example, CAN, UART, USB). In this application note, UART is used as an example.

This application note outlines general guidelines for creating an IAP application. The STR7xx Eval Boards were used to validate the IAP driver.

Software is provided and is available on http://www.st.com/mcu

January 2007

Rev 3

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www.st.com

Contents	AN2078

Contents

1	IAP overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 3
	1.1	Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3
	1.2	IAP driver description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3
2	Running the IAP driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5
	2.1	HyperTerminal configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
	2.2	Triggering execution of the IAP driver . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
3	IAP driver menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6
	3.1	Download image to internal Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
	3.2	Execute the new program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
4	STR7xx IAP implementation Summary . . . . . . . . . . . . . . . . . . . . . . . . . .		7
5	User program conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		8
6	IAP restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		9
7	How to use the IAP driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		10
8	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		12

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AN2078	IAP overview

1 IAP overview

1.1Principle

The IAP driver must be programmed by the user in the Flash base address (0x00) via JTAG using a flasher toolset.

Using the UART, the IAP driver loads a binary file from the HyperTerminal to the STR7xx internal Flash, and then jumps to execute it.

1.2IAP driver description

The following table shows the IAP driver code size for each STR7xx MCU.

STR71x	STR73x	STR75x
7.2 Kbytes	8.3 Kbytes	5.8 Kbytes

The IAP driver contains a set of source files:

●main.c: where the UART initialization and PLL configuration are set. Then, a main menu is executed from the common.c file.

●common.c: contains display functions and the main menu routine. The main menu gives the choice between loading a new binary file and executing the binary file already loaded.

●ymodem.c and download.c: they allow all data to be received from the HyperTerminal application (using the YMODEM protocol1)), then loaded into STR7 internal RAM. In the event of a failure in data receival, the ‘Failed to receive the file’ error message is displayed on the HyperTerminal window. However, if successful, the data is then programmed into internal Flash at the appropriate address. A comparison between internal RAM and internal Flash contents is performed to check the data intergrity. If there is any discrepency, the ‘Verification failed’ error message is displayed on HyperTerminal window. Other error messages are also displayed when the image size is higher than the allowed space memory and when there is an abort by the user.

Note: 1 Ymodem protocol sends data in 1024-byte blocks. A check for errors in data blocks transmitted to the STR7xx Internal RAM is applied: A comparison between the transmitted and received data is achieved. Blocks received unsuccessfully are acknowledged with a NAK (Negative Acknowledgement). For more details about the Ymodem protocol, refer to existing documentation.

●Some STR7xx Standard library and Flash library files.

A pin connected to a push button is used to select between jumping to the user application and executing the IAP for reprogramming purpose:

●Push button is not pressed at reset: jump to the user application

●Push button is pressed at reset: the IAP main menu is displayed

Figure 1 shows the IAP flowchart.

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IAP overview							AN2078
Figure 1. FlowChart of the IAP Driver
			Start
						No
		Push button is
		pressed?

Yes

Initialize the STR7 UART & PLL

Display the IAP Main Menu

	Download				Jump to User Program
		Download or
			Jump?
Receive a binary file

No Success

Yes

Program the internal Flash

		No			All data		Yes
					programmed
					successfully?
Display the error
message ‘Failed
to receive the
file’
				Display the name and the size of
					the received file
	Display the error message
	‘Verfification failed’

Jump to the User Program

User Application

Software

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