Execution environments

Execution environment: what the target board provides to run an application.

Bare metal

You write all the code:

• Configure and use interfaces and peripherals
• Define how to run several concurrent tasks
• Define how to share data between tasks
• Etc.

• Nowadays, an abstraction layer is provided by almost all microcontroller manufacturers:
  • ⇒ Compatibility over a family of microcontrollers
  • ⇒ A little bit easier to use peripherals and interfaces
  • Arm: CMSIS
  • Silicon Labs: (Part of) Simplicity SDK
  • STMicroelectronics: HAL + LL
  • Espressif: (Part of) ESP-IDF
  • Etc.

Real-Time Operating System (RTOS)

• Provides real help to run concurrent tasks, share data between tasks, etc.
• Allows for deterministic response time
• Uses very little memory
• No protection between tasks, nor between tasks and RTOS (no virtual memory)
• No way to modify the application without rebuilding and reflashing (well, not fully true)

Minimum required memory:

• RAM: a few KB
• Flash: a few KB
• Depends on the application

• FreeRTOS acquired by Amazon - 2017
• ThreadX acquired by Microsoft - 2019, transferred to the Eclipse Foundation, as open source - 2023
• Google and Meta support Zephyr

Available services: will be seen farther.

Operating System (OS)

• Mainly: Linux
• Similar to a desktop computer environment:
  • Package manager, to install new applications
  • Graphical user interface is possible

Minimum required memory:

• RAM: a few MB or a few tens of MB
• Depends on applications

Usually:

• RAM: from 512 MB to 8 GB
• Flash card: from 1 GB to 8 GB

• Linux typically requires an MMU (Memory Management Unit) ⇒ virtual memory
• The kernel can be configured to work without one
  • Thanks to μClinux project
  • Beware about applications compatibility

Latest news: real-time is now supported by mainline Linux kernel.

⇒ "standard" Linux now can provide deterministic response time.

Practice session 01

Build and run an Hello World application for the EFR32xG24 Dev Kit.

Execution environment: bare metal.

EFR32MG24

xG24 Dev Kit

Reference documentation

• Microcontroller:
  • EF32MG24 Wireless SoC Family Data Sheet (132 pages)
  • EFR32xG24 Wireless SoC Reference Manual (1152 pages)
• Board:
  • xG24 Dev Kit User's Guide
  • Schematic - Revision A01
• Sofware:
  • Developer Documentation:
    • Simplicity Studio 5 User's Guide
    • Platform (SDK)

Development environments

Several possibilities:

• Simplicity Studio v5 (SSv5) - based upon Eclipse IDE
• VS Code + extension
• ...

We will use SSv5.

SSv5

Practice session 01 - step 1

• Using git, clone the embedded-systems-for-ML GitHub repository:

  
                  $ git clone https://github.com/PascalBod/embedded-systems-for-ML.git
                

• Follow the instructions provided by the embedded-systems-for-ML/practice-sessions/01-HelloWorld-step1/README.md file.

Debugging

Debugging: process of finding the root cause of a bug.

Always try to reduce time devoted to debugging. How to do this is not part of this course, even if it contains some related information.

Generic architecture

• Microcontroller controlled by the debug probe
• JTAG: an industry standard, initially developped for verifying printed circuit boards (PCB)
• SWD: an Arm standard, fully debug oriented
• Debug probe controlled by the debugger server
• Debugger client used to send commands: run, pause, step, set breakpoint, etc.

For most of the dev boards, a simple probe is part of the board:

Practice session 01 - step 2

• Follow the instructions provided by the embedded-systems-for-ML/practice-sessions/01-HelloWorld-step2/README.md file.