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lAP overview
1
lAP overview
Theory of operation
In-Application Programming(IAP)is a means of upgrading firmware in the field using the
MCU communication interfaces like Uart. USB. can. ethernetetc
When you boot the microcontroller, you can choose to put it in IAP mode in order to execute
the lAP code or else, in normal mode, start to execute the application code. both the IAP
code and the application code are reside in the embedded Flash memory of the
microcontroller. Usually the laP code is stored in the first pages of the McU Flash, and the
user application code occupies the remaining Flash area
The lAP operation flow is described in the following figure
Figure 1. lAP operation flow
MCU reset
Enter lAP
Execute application code
mode?
lAP initializatio
lAP
No
Request
Ye
Receive bina
age and
program it into user Flash
area
12
lAP using the mcus ethernet interface
When it is available, Ethernet is often the preferred interface for implementing lAP capability
in an embedded application. The advantages are
o High speed communication interface(10/100Mbit/s)
Remote programming through the network (LAN or Wan)
Standardized application protocols on top of the TCP/IP stack that can be used for
implementing the laP like Ftp Tftp, Http,
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1.3
Implementing lAP over Ethernet on the STM32F107
This application note describes two solutions that implement lAP for the STM32F107 using
the ethernet communication peripheral
lAP using TFTP (Trivial File Transfer Protocol)
laP using Http(HypeRtexT Transfer Protocol
Both solutions run on top of the LwIP stack(v1.3. 1) which is a light-weight implementation of
the tCP/iP protocol suite
1.3.1
lAP method using TFTP
The lAP method using TFTP is widely used in embedded applications that require a
firmware upgrade capability(for example in embedded Linux bootloaders
TFTP is a simple file transfer protocol working on top of the UdP transport layer and it is
mainly intended to be used on a LAN environment. It is based on a client/server
architecture, where a client will request a file transfer (read or write operation) from a file
server
In our case, a simple TFTP server is implemented on top of the LwlP stack, this server only
processes write requests coming from a Pc tFTP client
132
lapmethodusinghttp
Firmware upgrade through Http protocol is less common than with Tftp but it can be an
useful solution, when remote programming over the Internet is needed. In this case TCP
transport protocol is needed to ensure optimum operation
Http which works on top of Tcp, offers a way of sending a binary file from a web client
(example: Mozilla Firefox or Microsoft Internet Explorer) using HTML Forms, it is called
Http File-upload(rfc 1867)
The next sections of this document, give more details about the implementation of both IAP
methods and an explanation of how to use the software
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MAP using TFTP
lAP using TFTP
2.1
TETP overview
Trivial File Transfer Protocol (TFTP) is a simple file transfer protocol, working on top of UDP.
A file transfer is initiated from a TFTP client which sends a Read or Write request to a TFTP
server
When the server acknowledges the request, file data transfers start. The data is sent in fixed
size blocks( for example in blocks of 512 bytes)
Each transferred data block must be acknowledged by the recepient, before the next block
can be sent. The acknowledge mechanism is based on the block number sent with each
data block
a data block with less than the fixed block size indicates the termination of the file transfer
Figure 2 describes the format of the various TFTP packets
Figure 2. TFTP packets
2 bytes
String 1 byte
RRQ/RQ packet
Opcode File name
Mode
2 bytes 2 byte
Data packet
2 bytes
ACK packet
Opcode Block+#
2 bytes 2 b
String 1 byte
Error packet
Opcode
Error
code
0
message
The TFTP opcodes are listed in Table 1.
Table 1. TFTP opcodes
Opcode
Operation
OX1
Read request (RRQ)
0x2
Write request (WRQ)
0X3
Data
0X4
Acknowledgment(ACK
0x5
Error
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lAP using TFTP
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22
Implementing lAP for the STM32F107 using TFTP
This IAP implementation consists of a basic TFTP server on top of the LwlP TCP/P stack
This server responds to file WrITE requests received from a remote TFTP client(PC)
TFTP READ requests are ignored
Instead of writing received files to a filesystem which is normally what tFtP is used for, the
server writes the received data blocks into the MCu Flash(in the user Flash area)
Note
In this implementation the data block size is fixed to 512 bytes
The following flowchart gives an overview of the IAP operation using TFTP.
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MAP using TFTP
Figure 3. Flowchart of lAP using TFTP
Enter laP mode
TFTP server initialization
TFTP Write
No
quest?
Erase the total user flash area
Send Ack
Data packet
No
Received
Write data block to flash
Send ack
Last data packet
End of file transfe
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2.3
Using the software
In order to test the lAP through TF TP, please ensure you follow these steps
1. Be sure of the correct jumper settings in the STM3210C_EVAL board(see Table 2)
2. In the main. h file uncomment the option "USE_lAP_ TFTP. Also, depending on your
needs, you can uncomment/comment other options like " USE_ DHCP"or"USE_LCD"
3. Recompile the software. Using the generated map file, be sure that there is no overlap
between the iAP code area(starting from address OXO)and the user Flash area
starting from address: USER_FLASH_FIRST_PAGE_ ADDRESS (defined in main h
4. Program the software in the STM32 Flash and run it
5. To enter IAP mode, press and then release the Reset button while keeping the Key
button pressed
6. If"USE_LCD"is defined in main. h file then, the LCD screen displays a message
indicating that IAP mode has been entered. Also if dHCP is used (USE_DHCP defined
in main. h), a message is displayed on the LCD screen indicating the success or failure
of dhcp ip address allocation
7. After iP address assignment (either static or dynamic address), the user can start the
IAP process
8. On the PC side open the TFTP client(for example TFTPD32), and configure the TFTP
server address(host address in TFTPD32
9. Browse for a binary image to load in the STM32 Flash(two binary images are provided
as examples in the /project/binary folder
10. Start a file write request by clicking the"Put" button in the tFTPD32 utility
11. When USE_LCD is enabled, the progress of the lAP operation is shown on the LCD
12. At the end of lAP operation, you can reset the evaluation board and run the application
that you have just programmed in the STM32 Flash
Figure 4. TFTPD32 dialog box
TItpd32 by Ph Jounin
Current Directory c:
Server interf aces 192.168.0.1
T p Server Ttp Client DHCP server Syslog ser
Hast192.1680.11
ort
Local file
Remate file
512
block +98
jet Pu
Er
囗■■■■■■■
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lapusinghttp
3
IaP using Http
Http file upload overview
File upload using Http is defined in Rfc1867. thIs method of uploading files is based on
HTML forms. To send raw binary data, the HTML POST method is used instead of the gET
The following is an example of HTML code for implementing form-based file upload
< form action ="/upload. cgi" enctype="multipart/ form-data"method="post">
Please specify a binary file to upload into sTM32F107 flash:
