STM32 Firmware Development Guide: From MCU Selection to Testing and Deployment
Introduction
The STM32 microcontrollers are very popular among embedded products because they incorporate processing capabilities, connectivity options, low-power performance, and real-time control in a single device. The examples of such products include industrial control systems, IoT solutions, consumer electronics, and instruments. In any case, STM32 microcontrollers serve as a convenient platform for developing a connected and intelligent solution.
But choosing the right STM32 microcontroller is just one aspect of the embedded product development process. To have reliable products, one needs to integrate firmware architecture, peripheral drivers, communication protocols, debugging, testing, and optimization into a whole system.
This guide introduces the major steps of STM32 firmware development and discusses what engineers need to take into account when they develop embedded products from scratch.
Definition of STM32 Firmware Development
STM32 firmware development is an activity in which embedded software is created for control of an STM32 microcontroller that interacts with the rest of the hardware.
The firmware can manage different peripherals like:
-GPIO
-Timers
-ADC and DAC
-UART
-SPI
-I2C
-CAN
-USB
-Ethernet
-PWM
-Sensors and actuators
-Memory units
Depending on the requirements of the product, the STM32 firmware can be executed directly by the microcontroller as a bare-metal program, or together with a real-time operating system such as Free RTOS and any other supported RTOS.
The idea is not only to have the microcontroller running some code. The firmware should work correctly within the limitations of the memory, time, power, communications, and environment of the final product.
Why STM32 in Embedded Devices?
STM32 stands for a large variety of microcontrollers tailored for various demands of embedded products. Various STM32 series have different combinations of processing capability, memory, peripheral units, communication interfaces, power consumption characteristics, and packages.
Therefore, STM32 can be used in such applications as:
Industrial automation devices
IoT gadgets
Motors control systems
Measurement and instrumentation devices
Intelligent sensors
Consumer electronics
Power management devices
Medical electronics
Robotics
Communication devices
The appropriate MCU must be chosen based on product demands and not on the basis of highest MCU performance.
Step 1: Determine the Needs of the Firmware and Hardware
The ideal STM32 firmware project usually starts even before writing code. The engineers first have to define the hardware and product needs.
Among the most important questions are:
-What does the device have to do?
-Which STM32 series and MCU is going to be used?
-How much Flash and RAM will be needed?
-Which peripherals are needed?
-Which communication protocols will be necessary?
-What are the timing requirements?
-What are the power consumption requirements?
-Is an RTOS required for the device?
-How will the firmware updates be done?
-What are the security requirements?
-What is the environment the product is supposed to operate under?
All of the above affect the firmware architecture.
Step 2: Choose STM32 MCU and Development Environment
Many options of STM32 microcontrollers are available. The choice of a right MCU requires balancing several factors, including performance, memory size, peripheral availability, power consumption, packaging, costs, and future product requirements.
It is necessary to choose a development environment too.
For particular tasks, engineers may use various tools like STM32CubeIDE and ST development software, along with proper compilers, debuggers, programmers, and development hardware boards.
A common setup may be composed of:
STM32 development board or custom PCB
Development IDE and compiler toolchain
ST-LINK debugger/programmer or other compatible device
Oscilloscope
Logic analyzer
Multimeter
Protocol analyzers when needed
Version control system
Automated build and test system
The exact toolchain depends on the product and development process.
Step 3: Define the Architecture of the Firmware
Architecture of the firmware defines the organization of the software and interaction between the software components.
The simplest approach is a bare metal architecture based on a main loop, interrupts, peripheral drivers, and application.
A more complicated one might need the RTOS.
The general architecture can include:
Application layer
It includes product-specific functionality and business logic.
Middleware layer
It provides such functionality as communication stacks, file systems, network protocols, or protocol handlers.
Hardware abstraction / Board Support Package
It offers a structured way of interacting between the application and underlying hardware.
Device Drivers
It controls sensors, displays, memories, communication interfaces, and other devices.
Hardware
It consists of the STM32 microcontroller and its attachments.
A good architecture simplifies the testing, maintenance, extension, and porting of the firmware to another hardware version.
Step 4: Peripheral Driver Development
Peripheral drivers enable the firmware to interact with the STM32 hardware.
The product may include:
-GPIO drivers for digital I/Os
-ADC drivers for reading sensors
-PWM drivers for controlling motors or actuators
-UART drivers for serial communication
-SPI for displays and external sensors
-I2C drivers for peripherals
-CAN for industrial or automotive applications
-USB for communication with the device
-Ethernet for networking capabilities
The design of the driver needs to take into account initialization, timing, error handling, interrupt behavior, integrity, and recovery.
Even if a driver works well in a basic laboratory test, it might need further testing in operational conditions.
Step 5: Communication Protocols Integration
A number of STM32 parts will require interaction with other parts.
Typical communication interface includes UART, SPI, I2C, CAN, USB, Ethernet, and wireless modules interfaced using suitable communication interfaces.
On a high-level basis, the firmware might also require protocols such as:
-Modbus
-MQTT
-TCP/IP
-HTTP
-BLE based communication
-Lo Ra based communication
It all depends on the application.
For instance, for an industrial controller, determinism and ruggedness will be more essential than an IoT sensor that operates on a battery.
Step 6: Choosing Between Bare Metal and RTOS Firmware
One of the critical architectural considerations involves choosing between bare-metal firmware and RTOS-based firmware.
Bare-metal firmware
Bare-metal development is relevant for simpler systems that have less demanding control.
Some of the potential advantages of bare-metal firmware are:
-Low overhead
-A simple architecture
-Hardware control
-Predictable resource utilization
-RTOS-based firmware
RTOS can be applied when the product requires multiple tasks that operate concurrently and that have certain timing constraints.
Some examples include such tasks as:
-Sensing
-Processing
-Communicating
-Monitoring system status
-Controlling outputs
-Logging data
RTOS can arrange the above tasks as separate threads and schedule and synchronize them.
Company's capabilities of firmware development involve RTOS and bare-metal firmware development, as well as BSP, drivers development, porting, optimizations, and system integration.
Challenges Often Encountered When Developing STM32 Firmware
Despite its flexibility, embedded project development using STM32 can be accompanied by major challenges.
Integration of Hardware and Firmware
The reason behind a firmware problem may be a faulty hardware design, improper component setup, signal integrity, or power behavior.
Resource Constraints
Restrictions in memory and processing power need proper architecture and optimization.
Timing Requirements
Real-time applications might require precise timing and predictable reaction.
Communication Reliability
There could be a failure of communication interface due to configuration issues, electrical interference, timing issues, or protocol errors.
Firmware Maintainability
Poorly organized firmware becomes hard to update with further product development.
This is the list of reasons why developing embedded firmware needs tight collaboration between hardware, firmware, testing, and product engineers.
Development of STM32 Firmware for Various Products
Architecture of the firmware shall be based on practical use of the product.
Industrial Controllers
Industries could have needs for deterministic control, communication, diagnosis, and interface such as CAN or Modbus.
Internet-of-Things (IoT) Products
IoT products could have needs for sensor handling, wireless communication, power consumption, security, and cloud communication.
Measurement and Instrumentation Products
Instrumentation products could put more attention on ADC capability, calibration, accuracy, data processing, and communication.
Motor Control Products
Motor control products could have needs for precise PWM creation, ADC sampling, timing, feedback processing, and real-time response.
Consumer Electronic Products
Consumer products could have needs for user interface, power consumption, communication, reliability, and fast development cycle.
When Should a Firm Think About Developing Its Own STM32 Firmware?
The development of customized firmware can be considered when the product demands features that cannot be fulfilled with generic firmware.
Some of the situations where customized firmware can play a role include the following:
-Product-specific hardware control
-Communication protocols unique to the company
-Customized sensors
-Real-time operations
-Power efficiency
-Security features specific to the product
-Modifying the existing firmware
-Firmware porting
-Maintenance
-Firmware to work with customized hardware
The important thing is to develop the firmware based on the product and not the other way round.
Selection of an STM32 Firmware Development Partner
In picking an embedded firmware development vendor, there are other things apart from technical skills to look out for.
Consider whether the engineering partner is aware of:
-Hardware and firmware development
-MCU architecture
-RTOS and bare-metal development
-Peripheral drivers
-Communications protocol
-Debugging and testing
-Security
-Production needs
-Maintenance
Good firmware development process should have documentation, version control, testing, and good communication between the engineering teams.
Conclusion
The development of STM32 firmware is not just programming a microcontroller, but includes requirements definition, architecture, peripheral interaction, communication, debugging, testing, optimization, security, and production support.
Properly designed firmware architecture can increase the reliability, maintainability, and adaptability of an embedded product in accordance with the changing requirements.
For companies that produce custom electronic devices, cooperation with an experienced embedded engineering team will allow making connections between firmware and hardware, communication interfaces, testing needs, and general product development process.
Companies such as, offer services of embedded firmware development including system architecture, custom firmware development, RTOS and bare-metal applications, BSP and device drivers, porting and optimization, and system integration.
Learn more about embedded firmware development
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