We’ve successfully deployed a serie of Raspberry Pi’s running a Rust application to control GPIO pins which dispense coins through a coin dispenser and controls relays that open magnetic doors via the self-service kiosks build by our partner Qiox. This setup has proven robust and versatile. However, there are scenarios where switching to a more dedicated embedded system, such as an STM32 microcontroller, might be more appropriate. In this post, we’ll explore the strengths of our current system and identify situations where a transition to a different hardware platform would be beneficial.
The Power of Raspberry Pi with Rust
Versatility and Ease of Use
One of the greatest strengths of the Raspberry Pi is its versatility. With its Linux-based operating system, the Raspberry Pi provides a familiar environment for developers, making it easier to implement complex applications. Rust, known for its performance and safety, is an excellent choice for controlling GPIO pins directly through the HAL (Hardware Abstraction Layer). This combination allows us to set and toggle pins and play sounds, all while monitoring system performance through Grafana.
Comprehensive Monitoring
Our system leverages Grafana for real-time monitoring, providing insights into logs, traces and metrics. This is invaluable for debugging and optimizing the application, ensuring that any issues can be quickly identified and addressed. The ability to monitor the system so closely is one of the key advantages of using a Raspberry Pi with Rust.
Development Speed
The development speed on a Raspberry Pi is significantly faster compared to traditional embedded systems. The extensive libraries and community support available for both Rust and the Raspberry Pi ecosystem mean that developers can quickly find solutions and implement features. This rapid development cycle is particularly beneficial in the prototyping phase or when the project requirements are still evolving.
Cost Efficiency for Low Volumes
For small-scale deployments or projects with lower unit volumes, the Raspberry Pi offers a cost-effective solution. The upfront costs and development time associated with STM32 microcontrollers can be higher, especially for low-volume projects. The Raspberry Pi, with its built-in peripherals like Wi-Fi, Ethernet and Bluetooth, often provides a more economical choice when considering the overall development and integration costs.
Non-Critical and High-End Small Business Applications
The Raspberry Pi excels in non-critical applications and high-end solutions for small businesses. It comes with “batteries included,” offering built-in Wi-Fi, Ethernet, Bluetooth and an extensive array of GPIO pins. This makes it ideal for sophisticated small business solutions that require robust connectivity and integration without the need for additional hardware. Whether you’re developing a smart kiosk, an advanced home automation system or a small-scale industrial controller, the Raspberry Pi delivers a comprehensive, high-performance platform that meets diverse needs.
When to Consider Switching to STM32
Power Consumption
One of the primary reasons to switch to an STM32 microcontroller is power consumption. The Raspberry Pi, being a full-fledged computer, consumes significantly more power than dedicated microcontrollers. For battery-operated devices or applications where power efficiency is crucial, the STM32 family would be a better fit. These microcontrollers are designed to run on minimal power while providing sufficient processing capabilities for most embedded tasks.
Real-Time Requirements
In applications requiring real-time performance, such as motor control or precise timing tasks, the deterministic behavior of microcontrollers like the STM32 is essential. While the Raspberry Pi can handle many tasks efficiently, its non-real-time operating system introduces latency and jitter that might be unacceptable for time-sensitive applications.
Cost Sensitivity at Scale
For large-scale deployments, the lower cost of microcontrollers becomes a significant advantage. The STM32 family is much cheaper than the Raspberry Pi when purchased in bulk, making them ideal for projects where the budget is a key concern. This cost efficiency is particularly important in commercial products where every dollar saved on hardware can improve overall profitability. However, it’s important to note that for low-volume projects, the development costs for STM32 can be higher, potentially offsetting the savings on hardware.
Space Constraints
Microcontrollers like the STM32 are much smaller than the Raspberry Pi. In applications where space is a limiting factor, such as wearable devices or compact consumer electronics, the smaller form factor of these microcontrollers is a clear advantage. Their small size allows them to be integrated into designs where a Raspberry Pi would simply not fit.
Long-Term Reliability
For applications that require long-term reliability and stability, microcontrollers are often preferred. The simpler architecture and lack of an operating system reduce the number of potential points of failure. In industrial automation or medical devices, where reliability is paramount, the robustness of microcontrollers like the STM32 makes them the preferred choice.
Transitioning to STM32
Development Considerations
Transitioning from a Raspberry Pi to an STM32 involves a shift in development practices. Unlike the Raspberry Pi, which supports a wide range of high-level programming languages and operating systems, microcontrollers require a more focused approach. However, with Rust, we can maintain safety and performance while targeting embedded systems.
Toolchains and Debugging
Developing for microcontrollers requires familiarity with different toolchains and debugging tools. Platforms like STM32CubeIDE provide a comprehensive environment for development but come with their own learning curves. Additionally, debugging microcontroller code often requires specialized hardware such as JTAG or SWD debuggers.
Peripherals and Integration
While transitioning, it’s essential to consider the peripherals and interfaces your application requires. The Raspberry Pi’s extensive GPIO and peripheral support are unmatched, so careful planning is needed to ensure the STM32 can interface with all necessary components. In some cases, additional hardware might be required to bridge the gap.
STM32 Variants:
The STM32 family offers a range of microcontrollers suitable for different applications:
- STM32F0: Cost-effective, suitable for low-end applications requiring simple and efficient processing.
- STM32F1: Balanced performance and power efficiency, widely used for general-purpose applications.
- STM32F2: Higher performance than F1, with additional features and better power efficiency.
- STM32F3: Advanced analog functions, ideal for applications requiring complex analog interfaces.
- STM32F4: High performance, suitable for general-purpose applications with demanding processing needs.
- STM32F7: Very high performance, suitable for applications requiring extensive processing power.
- STM32H7: Dual-core and high performance, used in applications requiring significant processing capabilities and real-time performance.
- STM32G0: Ultra-low power, suitable for battery-operated applications.
- STM32G4: Performance and efficiency balance, suitable for mixed-signal applications.
- STM32L0: Ultra-low power, suitable for applications requiring long battery life.
- STM32L1: Low power, with additional features for medical and metering applications.
- STM32L4: High performance with ultra-low power, suitable for advanced low-power applications.
- STM32L5: Enhanced security features, ideal for IoT and security-sensitive applications.
- STM32WB: Integrated wireless communication, suitable for IoT applications with Bluetooth or Zigbee.
Choosing the right variant depends on the specific needs of your project, such as computational requirements, power constraints and peripheral needs.
Choosing the Right Platform
Consider a project involving environmental monitoring in a remote location. Initially, a Raspberry Pi might be used for prototyping due to its ease of use and flexibility. As the project moves towards deployment, the need for low power consumption and long-term reliability becomes apparent. Switching to an STM32 microcontroller allows the device to run on solar power with battery backup, providing a more sustainable and reliable solution for remote monitoring.
Conclusion
Choosing the right hardware platform for your project is a critical decision that impacts development time, cost and overall performance. Our experience with a Raspberry Pi running a Rust application has shown its strengths in versatility, ease of use and comprehensive monitoring capabilities. However, there are clear scenarios where switching to a dedicated embedded system like an STM32 is advantageous, particularly in terms of power efficiency, real-time performance, cost, space constraints and long-term reliability.
By carefully evaluating your project’s requirements and considering the strengths and limitations of each platform, you can make an informed decision that aligns with your goals and constraints. Whether you stick with the Raspberry Pi or transition to a microcontroller, the key is to leverage the right tool for the job, ensuring your project succeeds in both development and deployment.