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Discovery kit with STM32MP157x MPU Series

This variant currently supports the following boards:

This port targets the Cortex-M4 coprocessor. Note that the coprocessor is not a stand-alone microcontroller: the Arduino firmware for the coprocessor must be managed by the host Linux (Cortex-A side). In other words, Cortex-M4 Engineering mode is not supported and only Production mode is supported.

Because every OS may have different software configurations (especially Device Tree) not all Linux distributions for these boards are supported. The currently supported distributions are the following:

Note

  • Other distributions not listed here may run Arduino firmware but they are not tested.
  • The first two OSes should select stm32mp157c-dk2-m4-examples-sdcard boot mode (or device tree configuration) on boot time.
  • stm32mp157c-dk2-sdcard boot mode is also known to work but it is not guaranteed. See ST Wiki page on boot mode for more detail. If you are using it for your own OS, see the Linux Device Tree considerations section.

How to use

After Verify and Upload, you will see a message similar to the following in Arduino IDE:

<Arduino build output path>/run_arduino_<sketch name>.sh generated successfully.
This file should be uploaded manually by SCP, SFTP, Kermit, or etc.
Then run "sh ./run_arduino_<sketch name>.sh start" command in the board's console.
For detailed instructions, please visit:
    https://github.com/stm32duino/Arduino_Core_STM32/tree/master/variants/STM32MP157_DK/README.md

<Arduino build output path>/run_arduino_<sketch name>.sh looks like this for Blink example:

  • Windows:

    C:/Users/%USERNAME%/AppData/Local/Temp/arduino_build_668148/run_arduino.Blink.sh

  • Linux/macOS:

    /tmp/arduino_build_668148/run_arduino_Blink.sh

In this example, the user must upload <Arduino build output path>/run_arduino_<sketch name>.sh file manually. Uploading instruction is described later in the Uploading section.

After uploading the user can use sh run_arduino_<sketch name>.sh start in the console of host Linux via either SSH or Serial Console, to run the Arduino firmware.

Note

  • sh run_arduino_<sketch name>.sh start is a one-shot command, the Arduino firmware only runs for the current boot. If you want to make it run after reboot, you need to use sh run_arduino_<sketch name>.sh install command.

run_arduino_<sketch name>.sh help page summary:

Usage: sh run_arduino_<sketch name>.sh [start|stop|restart|generate|install|uninstall]

run_arduino_<sketch name>.sh is a helper script that helps managing an Arduino binary
file for the coprocessor using remoteproc framework.

sh run_arduino_<sketch name>.sh start
    Upload the binary to the coprocessor then start it.
    This command must be executed while the script contains the binary
    after generate command is run.

sh run_arduino_<sketch name>.sh install
    Run the binary on boot automatically by installing a systemd service.

sh run_arduino_<sketch name>.sh uninstall
    Uninstall the autostart service.

sh run_arduino_<sketch name>.sh stop
    Stop the coprocessor.

sh run_arduino_<sketch name>.sh restart
    Restart the coprocessor.

See the source code run_arduino_gen.sh for the full help page and the more details about the run_arduino_<sketch name>.sh generated.

run_arduino_gen.sh is the shell script that produces a copy of the script called run_arduino_<sketch name>.sh but with the sketch binary self-contained.

Pin mapping

The boards have two pin headers: Raspberry Pi HAT headers and Arduino shield headers. This project currently supports Arduino Shield headers only, leaving RPi HAT headers for the Linux applications.

Note that PWM N channel (e.g. TIM1_CH3N) outputs negative output to the corresponding channel, meaning it outputs inverted duty cycle.

Feature ST Arduino Arduino ST Feature PWM
SCL PA_11 I2C5-SCL TIM1_CH4
SDA PA_12 I2C5-SDA
Varef
NC 13 PE_12 SPI4-SCK TIM1_CH3N
5V 12 PE_13 SPI4-MISO TIM1_CH3
RST 11 PE_14 SPI4-MOSI TIM1_CH4
3.3V 10 PE_11 SPI4-SS TIM1_CH2
5V 9 PH_6 TIM12_CH1
GND 8 PG_3
GND
Vin 7 PD_1
6 PE_9 TIM1_CH1
ADC1_IN0 PF_14 A0 5 PD_15 TIM4_CH4
ADC1_IN1 PF_13 A1 4 PE_10 TIM1_CH2N
ADC1_IN6 ANA_0 A2 3 PD_14 TIM4_CH3
ADC1_IN2 ANA_1 A3 2 PE_1
ADC1_IN13 PC_3 A4 1 PE_8 UART7-TX TIM1_CH1N
ADC1_IN14 PF_12 A5 0 PE_7 UART7-RX

There are additional pins for LEDs and buttons.

ST Arduino Arduino (cont.) Comment
PA_14 16 / LED_GREEN USER1_BTN / USER_BTN Active Low, LED LD5, also connected to B3 button
PA_13 17 / LED_RED USER2_BTN Active Low, LED LD6, also connected to B4 button
PH_7 18 / LED_ORANGE / LED_BUILTIN Active High, LED LD7

variant.h of the board has the complete information about the pinouts.

Uploading

As mentioned above run_arduino_<sketch name>.sh file have to be uploaded manually from the PC to the board's Linux file system in order to be executed on the board directly through the board's Linux console. There are many ways to upload the file.

Over Network

  • SCP and SFTP are good options to upload the file, since STM32MP1 board runs SSH server by default. There are a lot of online resources on how to use them on the internet. Here is the default SSH access information:
host: (Varies. Search online to learn how to figure it out.)
username: root
password: (none by default)

Over Serial

  • C-Kermit is a combined network and serial communication software package that allows users to transfer files over serial connection. The ST Wiki page on C-Kermit describes how to use it.

Linux Device Tree considerations

To use the Arduino firmware for a custom OS, the user need to take into account in the Linux Device Tree, since a peripheral cannot be shared between the Linux host and the Arduino firmware, and Arduino must occupy some peripherals.

For example, Arduino uses TIM1 for PWM analogWrite() implementation. The Device Tree must disable TIM1 for Linux usage like the following:

&timers1 {
	status = "disabled";
};

And then the Device Tree should enable TIM1 for the coprocessor, although this doesn't seems to be a strict requirement it is safer to do this:

&m4_timers1 {
	pinctrl-names = "rproc_default";
	pinctrl-0 = <&timer1_pins>;
	status = "okay";
};

stm32mp157c-dk2-m4-examples.dts is a great example to begin with. For the full list of peripherals used by the Arduino firmware, see PeripheralPins.c of the board.

Limitations

  • Ethernet and USB are not supported. Use them in the Linux host.
  • Currently there is no easy way for communication between the Linux host and Arduino coprocessor. There is ongoing work for virtual serial communications using OpenAMP rpmsg framework. Currently one possible way is to wire between UART7 (Arduino SCL/SDA pins) and USART3 (Linux RPi HAT GPIO14/GPIO15 pins), however, users should manually modify Linux Device tree to enable usart3 and recompile it.
  • I2C pins on Raspberry Pi HAT header (GPIO2 and GPIO3) are not available in Linux host. This is because the Discovery board shares I2C pins on Arduino header and those on the HAT header.
  • Early firmware loading from U-Boot stage is not supported. Only firmware loading on Linux boot stage by systemd supported. The binary itself may be loaded by U-Boot without any problems, but there is no out-of-box tool to configure U-Boot to load the firmware using Arduino IDE yet.
  • EEPROM library: Those devices do not have non-volatile memory. The emulation is done using RETRAM. Therefore data will be preserved only when VBAT is supplied (e.g. A coin battery is connected to CN3 on STM32MP157A_DK1) and the coprocessor is waken up from sleep. This implies that cold boot the board may cause data loss, even if VBAT is supplied. See discussions on RETRAM for more detail.