Running system on armv7m4-stm32l4x6-nucleo

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:


  • Now you should verify, what USB device on your host-pc is connected with the UART (console). To check that run:

  • On Ubuntu:

console ls -l /dev/serial/by-id


  • On macOS:

console ls -l /dev/tty.*


  • Open serial port in terminal using picocom

console picocom -b 115200 --imap lfcrlf /dev/tty[port]

How to get picocom and run it without privileges (Ubuntu 22.04)

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

To use picocom without sudo privileges run this command and then restart:

console sudo usermod -a -G tty <yourname>

How to get picocom (macOS)

console brew update &&\ brew 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 or 0.12. You can check it using

openocd -v

How to get openocd in version 0.11 (Ubuntu 22.04)

To install from the default repositoriy:

  • use apt-get

console sudo apt-get install openocd

  • check if the version is correct

console openocd -v

To install manually:

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

console cd openocd-0.11.0-rc2

  • install openocd

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

  • check if the version is correct

console openocd -v


How to get openocd (macOS)

  • install openocd

    console brew update &&\ brew install open-ocd

  • check if the version is correct

    console 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