9.6. Flashing a new firmware¶

Multiple solutions exist to flash the firmware, some use open source tools and others can use proprietary tools. We will focus here on using the openocd open source tool.

After building the wookey.hex file, use the following steps to flash it on the target board.

Note

For now, this help targets the STM32F407 Discovery board

9.6.1. Connect the board to the host¶

The board should be connected to the host via USB. You should see something like this when running lsusb command

Bus 001 Device 005: ID 0483:374b STMicroelectronics ST-LINK/V2.1

You can see the vendor and product id (here 0483 and 374b).

On Debian Stretch, the board is seen as the /dev/ttyACM0 device. You need some extra privileges to be able to access (read and write) that device. You may decide to be root (for example by using the sudo command) but it is usually safer to add your current user in the plugdev.

9.6.2. Connect OpenOCD to the board¶

The tools/ directory contains some configuration files for STM32 Discovery boards. To connect OpenOCD to the board, launch openocd command with the appropriate configuration file:

openocd -f tools/stm32f4disco1.cfg

Note also that the stm32f4disco1.cfg configuration file may fail. If so, try with the stm32f4disco0.cfg file. A tip is to compare the vendor and the product id returned by the lsusb command with the one found in the configuration file.

9.6.3. Flashing the device¶

When OpenOCD is successfully connected to the board, you can interact with it through its inner local server. This can be done with gdb or telnet. However, the simplest way to flash a new firmware is to use openocd command as describe below.

9.6.3.1. Using the telnet client¶

Connect the server listening on localhost:4444:

telnet localhost 4444

Then, it is possible to send some commands to the OpenOCD local server in order to interact with the board. To flash the board, use the following commands.

First, asks to the board to reset and to halt at startup, freezing the core on its first instruction so that flashing it is safe:

reset halt

Now you can flash the board with the new firmware:

flash write_image erase build/armv7-m/32f407discovery/32f407discovery.hex

Then, you can reset and start the board:

reset run

9.6.3.2. Using OpenOCD¶

It is possible to flash the firmware by using a subsequent configuration file in parameter:

openocd -f tools/stm32f4disco1.cfg -f tools/ocd_demo.cfg

The file tools/ocd_demo.cfg should contain:

init
reset halt
flash write_image erase build/armv7-m/32f407discovery/32f407discovery.hex
reset
shutdown

9.6.3.3. Using GDB¶

GDB connects to OpenOCD through localhost:3333 instead of localhost:4444:

$ arm-eabi-gdb
(gdb) target extended-remote 127.0.0.1:3333

For example, to debug the EwoK kernel:

target extended-remote 127.0.0.1:3333
mon reset halt
symbol-file build/armv7-m/32f407discovery/kernel/kernel.fw1.elf
b main
c

9.6.4. Other ways¶

You can also use the ST-link tool to flash the firmware, simply by using the st-flash tool of the st-link project.