Fixing problems in STM32 microcontrollers is a big part of making them work well. Let’s talk about some simple ways to find and solve these problems. We’ll look at ways to show what’s happening inside the microcontroller as it runs. There are some debug techniques (SWV, RTT, UART and Semihosting) used to inspect the firmware running on ARM-based MCUs:
| Debugging Method | Description | Communication | Speed | Direction | Dependency |
|---|---|---|---|---|---|
| Semihosting | Built-in ARM feature; enables communication with debugger console during debugging. | Through debugger console | Moderate | Uni-directional | Additional libraries and debug mode |
| Console Log | Forwards printf output to an external device through UART or USB for real-time monitoring. | UART or USB | Real-time | Uni-directional | Additional hardware (UART or USB connections) |
| Serial Wire View (SWV) | Dedicated Single Wire Output (SWO) pin for fast real-time output, available on Cortex-M3 and newer. | Through dedicated SWO pin | Fast | Uni-directional | Available on Cortex-M3 and newer processors |
| Real-Time Transfer (RTT) | Bi-directional communication with SEGGER Debugger for extremely fast real-time interaction. | Bi-directional communication with SEGGER Debugger | Extremely fast | Bi-directional | SEGGER Debugger support, SEGGER hardware requirements |
Semihosting
Semihosting is like a communication bridge between the STM32 microcontroller and your computer during debugging. The microcontroller sends messages to your computer, and you can see these messages on the debugger console.
- How it works: Additional libraries are needed to make semihosting work. When the microcontroller is in debug mode, it can output messages, such as printf statements, to the debugger console. This provides real-time insights into the program’s execution.
- Pros: Universally available on ARM chips. Allows for interaction with the debugger console.
- Cons: Increases code size due to additional library usage. Can be slower compared to other methods.
Console Log
This method involves forwarding printf output from the microcontroller to your computer through a connection, such as a UART (Universal Asynchronous Receiver-Transmitter) port or a Virtual COM port via USB.
- How it works: Printf statements in the firmware are sent to a native UART port or a Virtual COM port connected to your computer. This allows for real-time communication and debugging.
- Pros: Real-time communication. Versatile, as it can connect to different platforms through UART or USB.
- Cons: Limited by the baud rate for UART communication. Requires additional hardware for connection.
Serial Wire View (SWV)
SWV is a debugging feature that provides fast output using a dedicated Single Wire Output (SWO) pin on the microcontroller. It allows for real-time visualization of data during debugging.
- How it works: The SWO pin is used to transmit real-time data to the debugger, enabling developers to observe the microcontroller’s behavior quickly.
- Pros: Fast output using the SWO pin. Real-time visualization of data.
- Cons: Only available on Cortex-M3 and newer processors. Offers uni-directional communication.
Real-Time Transfer (RTT)
RTT is a debugging method that facilitates extremely fast communication between the microcontroller and the debugger. It is specifically designed to work with SEGGER Debugger.
- How it works: RTT enables real-time, bi-directional communication between the microcontroller and the debugger, allowing for quick and efficient debugging.
- Pros: Extremely fast communication. Real-time, bi-directional interaction.
- Cons: Requires support from SEGGER Debugger. Limited to SEGGER tools and hardware.
In summary, each printf debugging method on STM32 microcontrollers has its advantages and limitations. The choice depends on project requirements, available tools, and the need for real-time interaction or fast communication. Understanding these methods empowers developers to select the most suitable approach for effective firmware debugging.
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