ST AN3154 Instructions d'installation et d'utilisation

March 2010 Doc ID 17063 Rev 1 1/34

AN3154

Application note

CAN protocol used

in the STM32™ bootloader

Introduction

This application note describes the CAN protocol used in the STM32 microcontroller

bootloader. It details each supported command. For more information about the CAN

hardware resources and requirements for your device bootloader, please refer to the

“STM32 system memory boot mode” application note (AN2606).

Related documents

Available from www.st.com:

AN2606 “STM32 system memory boot mode”

www.st.com

Contents AN3154

2/34 Doc ID 17063 Rev 1

Contents

1 Bootloader code sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 CAN settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Bootloader command set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.1 Device-dependent bootloader parameters . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.2 Get command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 Get Version & Read Protection Status command . . . . . . . . . . . . . . . . . . 12

3.4 Get ID command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.5 Speed command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.6 Read Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.7 Go command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.8 Write Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.9 Erase Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.10 Write Protect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.11 Write Unprotect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.12 Readout Protect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.13 Readout Unprotect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4 Bootloader protocol version evolution . . . . . . . . . . . . . . . . . . . . . . . . . 32

5 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

AN3154 List of tables

Doc ID 17063 Rev 1 3/34

List of tables

Table 1. CAN bootloader commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 2. Bootloader protocol versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 3. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

List of figures AN3154

4/34 Doc ID 17063 Rev 1

List of figures

Figure 1. Bootloader for STM32 with CAN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 2. Check HSE frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 3. CAN frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 4. Get command: host side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 5. Get command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 6. Get Version & Read Protection Status command: host side . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 7. Get Version & Read Protection Status command: device side. . . . . . . . . . . . . . . . . . . . . . 13

Figure 8. Get ID command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 9. Get ID command: device side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 10. Speed command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 11. Speed command: device side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 12. Read memory command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 13. Read memory command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 14. Go command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 15. Go command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 16. Write Memory command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 17. Write memory command: device side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 18. Erase Memory command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 19. Erase Memory command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 20. Write Protect command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 21. Write Protect command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 22. Write Unprotect command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 23. Write Unprotect command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 24. Readout Protect command: host side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Figure 25. Readout Protect command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Figure 26. Readout Unprotect command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Figure 27. Readout Unprotect command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

AN3154 Bootloader code sequence

Doc ID 17063 Rev 1 5/34

1 Bootloader code sequence

Figure 1. Bootloader for STM32 with CAN

Once the system memory boot mode is entered and the STM32 device has been configured

(for more details refer to application note AN2606 “STM32 system memory boot mode”), the

bootloader code waits for a frame on the CANx_Rx pin. When a detection occurs the CAN

bootloader firmware starts to check the external clock frequency, Figure 2 shows the

flowchart of the frequency check.

&RAMEDETECTED

ON#!.X?2XPIN

7AITFORA

COMMAND

'%4CMD

ROUTINE

AI

#HECK(3%FREQUENCY

2$CMD

ROUTINE

OPTIONAL

2OUTINESFOR

LOADING

INTO2!-

'/CMD

ROUTINE

*0TO?!DDRESS

'/CMD

#OMMAND

RECEIVED

'%4CMD

Bootloader code sequence AN3154

6/34 Doc ID 17063 Rev 1

Figure 2. Check HSE frequency

Next, the code initializes the serial interface accordingly. Using this calculated baud rate, an

acknowledge byte (0x79) is returned to the host, which signals that the STM32 is ready to

receive commands.

3TARTCHECK(3%FREQUENCY

-ESSAGERECEIVED

WITHSTD)$X

ANDWITHOUTFRAME

ERROR

AIB

#ONFIGURE#!.BAUDRATEATKBPS

ASSUMINGTHAT(3%-(Z

)NITIALIZETIMEOUTAT^MS

$ECREMENTTIMEOUT

4IMEOUTX

#ONFIGURE#!.BAUDRATEATKBPS

ASSUMINGTHAT(3%-(Z

)NITIALIZETIMEOUTAT^MS

9E S

-ESSAGERECEIVED

WITHSTD)$X

ANDWITHOUTFRAME

ERROR

9E S

#ONFIGURE#!.BAUDRATEATKBPS

ASSUMINGTHAT(3%-(Z

)NITIALIZETIMEOUTAT^MS

-ESSAGERECEIVED

WITHSTD)$X

ANDWITHOUTFRAME

ERROR

$ECREMENTTIMEOUT

4IMEOUTX

9E S

%NTERANINFINITELOOPWAITING

FORANY#!.BOOTLOADERCOMMAND

'ENERATESYSTEMRESET

$ECREMENTTIMEOUT

4IMEOUTX

9E S

AN3154 CAN settings

Doc ID 17063 Rev 1 7/34

2 CAN settings

The STM32 CAN is compliant with the 2.0A and B (active) specifications with a bitrate up to

1 Mbit/s. It can receive and transmit standard frames with 11-bit identifiers as well as

extended frames with 29-bit identifiers.

Figure 3 shows a CAN frame that uses the standard identifier only.

Figure 3. CAN frame

In this application, the CAN settings are:

●Standard identifier (not extended)

●Bitrate: at the beginning it is 125 kbps; during runtime it can be changed via the speed

command to achieve a maximum bit rate of 1 Mbps.

The transmit settings (from the STM32 to the host) are:

●Tx mailbox0: On

●Tx mailbox1 and Tx mailbox2: Off

●Tx identifier: (0x00, 0x01, 0x02, v03, 0x11, 0x21, 0x31, 0x43, 0x63, 0x73, 0x82, 0x92)

The receive settings (from the host to the STM32) are:

●Synchronization byte, 0x79, is in the RX identifier and not in the data field.

●RX identifier depends on the command (0x00, 0x01, 0x02, 0x03, 0x11, 0x21, 0x31,

0x43, 0x63, 0x73, 0x82, 0x92).

●Error checking: If the error field (bit [6:4] in the CAN_ESR register) is different from

000b, the message is discarded and a NACK is sent to the host.

●In FIFO overrun condition, the message is discarded and a NACK is sent to the host.

●Incoming messages can contain from 1 to 8 data bytes.

Note: The CAN bootloader firmware supports only one node at a time. This means that CAN

Network Management is not supported by the firmware.

)$



$,#

.

#2#

 

%/&

!#+

3/&

242

)$%

R

!RBITRATIONFIELD #ONTROLFIELD $ATAFIELD #2#FIELD

!#+FIELD

)NTERFRAMESPACE

OROVERLOADFRAME

$ATAFRAMESTANDARDIDENTIFIER

.

AI

Bootloader command set AN3154

8/34 Doc ID 17063 Rev 1

3 Bootloader command set

The supported commands are listed in Ta bl e 1 below. Each command is further described in

this section.

Communication safety

Each packet is either accepted (ACK answer) or discarded (NACK answer):

●ACK message = 0x79

●NACK message = 0x1F

Table 1. CAN bootloader commands

Command Command

code Command description

Get(1)

1. Read protection – When the RDP (read protection) option is active, only this limited subset of commands is

available. All other commands are NACKed and have no effect on the device. Once the RDP has been

removed, the other commands become active.

0x00 Gets the version and the allowed commands

supported by the current version of the bootloader

Get Version & Read Protection

Status(1) 0x01 Gets the bootloader version and the Read

Protection status of the Flash memory

Get ID(1) 0x02 Gets the chip ID

Speed 0x03 The speed command allows the baud rate for CAN

run-time to be changed.

Read Memory 0x11 Reads up to 256 bytes of memory starting from an

address specified by the application

Go 0x21 Jumps to user application code located in the

internal Flash memory or in SRAM

Write Memory 0x31 Writes up to 256 bytes to the RAM or Flash memory

starting from an address specified by the application

Erase 0x43 Erases from one to all the Flash memory sectors

Write Protect(2)

2. See Section 3.1 below

0x63 Enables the write protection for some sectors

Write Unprotect(2) 0x73 Disables the write protection for all Flash memory

sectors

Readout Protect(1) 0x82 Enables the read protection

Readout Unprotect(1) 0x92 Disables the read protection

AN3154 Bootloader command set

Doc ID 17063 Rev 1 9/34

3.1 Device-dependent bootloader parameters

While the CAN bootloader protocol’s command set and sequences are the same for all

STM32 devices, some parameters are device-dependent. For a few commands, the value of

some parameters may depend on the device used. The concerned parameters are listed

below:

●PID (product ID), which changes with the device

●Valid memory addresses (RAM, Flash memory, system memory, option byte areas)

accepted by the bootloader when the Read Memory, Go and Write Memory commands

are executed

●Size of the Flash memory sector used when executing the Write Protect command

For more details about the value of these parameters for the device you are using please

refer to the “Device-dependent boot loader parameters” section in the “STM32 system

memory boot mode” application note (AN2606).

3.2 Get command

The Get command allows the host to get the version of the bootloader and the supported

commands. When the bootloader receives the get command, it transmits the bootloader

version and the supported command codes to the host.

Bootloader command set AN3154

10/34 Doc ID 17063 Rev 1

Figure 4. Get command: host side



7AITFOR!#+

OR.!#+

2ECEIVEMESSAGENUMBEROFBYTES

VERSIONCOMMANDS

%NDOFGETCOMMAND

.!#+

!#+

3ENDMESSAGEWITHSTD)$H

3TARTGETCOMMAND

AI

2ECEIVEMESSAGE"OOTLOADERVERSION

7AITFOR!#+

OR.!#+

2ECEIVEMESSAGE'ETCOMMAND

2ECEIVEMESSAGE3PEEDCOMMAND

2ECEIVEMESSAGE2EADCOMMAND

2ECEIVEMESSAGE'OCOMMAND

2ECEIVEMESSAGE7RITEMEMORYCOMMAND

2ECEIVEMESSAGE%RASEMEMORYCOMMAND

2ECEIVEMESSAGE'ET6ERSION

2EAD0ROTECTIONSTATUSCOMMAND

2ECEIVEMESSAGE'ET)$COMMAND

2ECEIVEMESSAGE7RITE0ROTECTCOMMAND

2ECEIVEMESSAGE7RITE5NPROTECTCOMMAND

2ECEIVEMESSAGE2EADOUT0ROTECTCOMMAND

2ECEIVEMESSAGE2EADOUT5NPROTECTCOMMAND

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