Running system on armv7m4-stm32l4x6-nucleo (ST STM32L4x)

This version is designated for STM32L4x6 processors with Cortex-M4 core. To launch this version the final flash image should be provided. The image is created as the final artifact of the phoenix-rtos-project building and is located in the _boot directory. The image consists of a kernel, TTY UART driver, RAM disk filesystem, and psh (shell).

See how to build the Phoenix-RTOS system image.

Development board

The easiest way to start programming hardware targets using Phoenix-RTOS is to get some of the evaluation boards with a specified target processor or microcontroller. In this case NUCLEO-L4A6ZG is the example of a board with stm32l4x6 microcontroller.

Connecting the board

To provide a power supply for the board and make flashing possible, you have to connect a USB to micro USB cable between your host pc and the development board (USB PWR port, also called CN1). To communicate with the board you will need to use a UART-USB converter, like PL2303 TA.

  • Connect TX, RX, and GND wires to the USART2 (called also USART_B) in the Nucleo board. For example, using PL2303 TA:
  • PL2303 TX (green) - Nucleo USART_B_RX
  • PL2303 RX (white) - Nucleo USART_B_TX
  • PL2303 GND (black) - Nucleo GND

Source: The Nucleo board's schematic, available on

  • Put the converter into your host PC's USB port

The picture below presents how the board should be connected:

  • Open serial port in terminal using picocom

picocom -b 115200 --imap lfcrlf /dev/ttyUSB0

How to get picocom (Ubuntu 20.04)

sudo apt-get update && \ sudo apt-get install picocom

You can leave the terminal with the serial port open, and follow the next steps.

Flashing the Phoenix-RTOS system image

To flash the image to the board you will need openocd in version 0.11. When installing openocd using apt-get version can be out of date (0.10). You can check it using

openocd -v

How to get openocd in version 0.11 (Ubuntu 20.04)

  • download openocd-0.11.0-rc2 from here
  • enter the downloaded directory

cd openocd-0.11.0-rc2

  • install openocd

sudo apt-get install libusb-1.0 && ./configure --enable-stlink && make && sudo make install

  • check if the version is correct

openocd -v

If you have openocd, next you can use the following script:

sudo phoenix-rtos-build/scripts/ _boot/armv7m4-stm32l4x6-nucleo/phoenix.disk

or use openocd directly:

openocd -f interface/stlink.cfg \
-f target/stm32l4x.cfg -c "reset_config srst_only srst_nogate connect_assert_srst" \
-c "program _boot/armv7m4-stm32l4x6-nucleo/phoenix.disk 0x08000000 verify reset exit"

The script can be modified to accommodate other SWD interfaces.

Using Phoenix-RTOS

Phoenix-RTOS will be launched and the psh shell command prompt will appear in the terminal with the serial port opened.

  • Note: You can also enter plo (Phoenix-RTOS loader) by pressing any button, for example, enter within some time after reset (using RESET B2).

To get the available command list please type:


To get the list of working processes please type:


See also

  1. Running system on targets
  2. Table of Contents