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10.1.3 Flashing the STM32 firmware
For convenience, mule.sh tool is available for controlling and flashing the STM32 microcontroller. Executing
the script, SoC resets microcontroller into DFU mode and then uploads the firmware binary to internal STM32
flash memory.
The tool is available here: https://git.embedded.cherry.de/som-tools.git/tree/mule.
To flash STM32 microcontroller using mule.sh, please follow the steps below.
1. Install mule.sh dependencies according to README.md
2. Upload mule.sh tool and mule.dfu firmware file to a device
3. Flash controller using the following command:
sudo ./mule.sh --flash mule.dfu
Note: It is highly recommended that one reboots the main SoC interacting with the companion microcontroller
after flashing to make sure device drivers are properly initialized.
10.2 Companion Controller 2 (ATtiny)
Controller is based on ATtiny microcontroller and provides additional features to the CPU, exposed via I2C. This
controller is a substitute for first controller, supports the same functions except CAN. As for the first controller,
it emulates standard ICs and does not need custom drivers on Linux.
Mule ATtiny controller supports the following features:
• RTC
• Temperature sensor
• Fan controller
For hardware details, please refer to Section 12.4.5 Companion Controller 2.
10.2.1 Internal connections
Mule ATtiny controller is connected to SoC via I2C bus and the following pins.
10.2.2 Flashloader mode
Flashloader mode allows writing to the internal ATtiny flash memory via I2C.
To enter flashloader mode:
1. Pull BOOT pin high
2. Cycle reset ATtiny using RST pin
v1.3.1
Page 36
Function
CPU Pin
Linux GPIO #
RST
GPIO3_A4
100
BOOT
GPIO3_A5
101
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