Troubleshooting AT32F405 USB HS Recognition Issues

Aug 3, 2025 by Viktoria Ivanova 51 views

AT32F405 USB HS Not Working: Troubleshooting and Solution

Introduction

In this article, we will delve into a specific issue encountered while working with the AT32F405 microcontroller and its USB High-Speed (HS) capabilities. Specifically, we'll be examining a scenario where a custom board based on the AT32F405 fails to be recognized by the host computer when attempting to use USB HS. This is a common problem that many embedded developers face, and it can be frustrating to troubleshoot. We'll explore the steps taken to diagnose the problem, the solution that was implemented, and the potential implications of that solution. This article aims to provide a comprehensive understanding of the issue and its resolution, offering valuable insights for anyone working with the AT32F405 and USB HS. So, if you're experiencing similar problems, this guide is for you! Let's get started and dive into the details of AT32F405 USB HS troubleshooting. We will cover the problem, the debugging process, and the fix that was implemented to get the USB HS working.

Understanding USB High-Speed (HS) and AT32F405

Before we dive into the specifics of the issue, let's quickly recap what USB High-Speed (HS) is and why it's important. USB HS, also known as USB 2.0, is a ubiquitous communication standard that allows devices to transfer data at speeds up to 480 Mbps. This makes it suitable for a wide range of applications, from connecting peripherals like keyboards and mice to transferring large files and streaming video. The AT32F405 microcontroller, like many modern microcontrollers, incorporates a USB HS interface, enabling it to communicate with host computers and other USB devices at these higher speeds. When working with embedded systems, getting USB HS to function correctly is often crucial for achieving the desired performance and functionality.

The AT32F405 series of microcontrollers from Artery Technology are based on the ARM Cortex-M4 core and offer a compelling blend of performance, features, and cost-effectiveness. These microcontrollers are used in a wide range of applications, including industrial control, consumer electronics, and medical devices. The USB High-Speed (HS) interface is a key feature of the AT32F405, allowing it to communicate with host devices at speeds up to 480 Mbps. This is significantly faster than the older USB 1.1 standard (12 Mbps) and allows for more demanding applications such as audio and video streaming, high-speed data transfer, and complex device emulation. However, setting up and troubleshooting USB HS on the AT32F405 can be challenging, requiring careful configuration of the microcontroller's peripherals and adherence to the USB protocol specifications. A proper understanding of the hardware and software aspects is essential for successfully implementing USB HS functionality. This often involves digging into the device datasheet, understanding the clock tree, and correctly configuring the USB PHY. Moreover, the software stack used to manage the USB communication plays a crucial role. Libraries like TinyUSB provide a higher-level abstraction, making it easier to implement USB device classes. When things go wrong, debugging can be intricate, requiring the use of USB analyzers, logic analyzers, and in-depth knowledge of the USB protocol.

Problem Description

The core issue at hand is that a custom board, built around the AT32F405 microcontroller, was failing to be recognized by a Windows 11 host computer when attempting to use the USB High-Speed (HS) interface. This means that when the board was connected to the computer via USB, the computer did not detect the device, and no communication could be established. This is a critical problem, as it prevents the board from interacting with the host system, rendering the USB functionality unusable. The developer, in this case, had implemented a custom firmware based on the TinyUSB library, a popular open-source USB device stack. The firmware was designed to leverage the USB HS capabilities of the AT32F405, but the failure to be recognized by the host indicated a fundamental issue in the USB configuration or hardware setup. This situation is not uncommon when working with custom hardware and embedded systems, as there are many potential points of failure, ranging from incorrect clock settings to misconfigured USB PHYs. To effectively troubleshoot, a systematic approach is required, starting with verifying the basic hardware connections and then moving on to examining the software configuration and USB protocol interactions. The lack of a UART interface on the custom board made debugging more challenging, as traditional debugging methods involving print statements over UART were not available. This necessitated a more focused approach, relying on code inspection and a deep understanding of the USB hardware and software stack. This also underscores the importance of having a good debugging setup in place during development, as it can save significant time and effort when issues arise. For instance, using a USB analyzer can provide valuable insights into the USB traffic, helping to pinpoint the source of the problem. Similarly, having a JTAG debugger allows for step-by-step code execution and inspection of the microcontroller's internal state.

The problem manifested as a complete failure of the host computer to recognize the custom AT32F405 board when connected via USB. This meant that the device did not appear in the device manager, and no USB enumeration occurred. The firmware running on the board was based on the TinyUSB library, a popular open-source USB stack, and was configured to use the USB High-Speed (HS) interface of the AT32F405. Despite this, the board remained undetected. This type of issue is often a result of a low-level configuration problem, such as incorrect clock settings, improper USB PHY initialization, or a mismatch between the hardware and software configurations. In such cases, the microcontroller may not be correctly signaling its presence to the host, or the host may be unable to establish a communication link due to protocol violations or timing issues. Debugging this type of problem can be particularly challenging, as there is often little or no feedback from the system. Traditional debugging techniques, such as printing debug messages over a UART interface, may not be available, as was the case in this scenario. This necessitates a more meticulous approach, involving a careful review of the hardware schematics, microcontroller datasheet, and USB protocol specifications. It may also be necessary to use specialized tools, such as USB analyzers, to capture and analyze the USB traffic between the device and the host. These tools can provide valuable insights into the communication process, helping to identify any protocol errors or timing violations. Furthermore, understanding the USB enumeration process is crucial. This involves the host sending specific requests to the device and the device responding with descriptors that describe its capabilities. If this process fails at any point, the device will not be recognized.

Troubleshooting Steps

To tackle this issue, the developer embarked on a systematic troubleshooting process, which is crucial for any embedded systems development. The initial step was to carefully review the hardware design, ensuring that the USB data lines, power supply, and clock signals were correctly connected and functioning within the specified tolerances. This involves checking the schematics, probing the board with a multimeter and oscilloscope, and verifying the crystal oscillator frequency. Next, the firmware configuration was scrutinized, paying close attention to the USB peripheral initialization, clock settings, and interrupt handlers. The TinyUSB library provides a well-structured framework for USB device development, but incorrect configuration can still lead to issues. Specifically, the developer examined the tusb_config.h file, which contains various configuration options for the library, including the selection of the USB port and the enabling of specific USB features. The code responsible for initializing the USB PHY (Physical Layer) was also reviewed, as this is a critical component for USB HS communication. The PHY is the interface between the microcontroller's USB controller and the external USB data lines, and its proper initialization is essential for establishing a reliable connection. Another important aspect of the troubleshooting process is to verify the power supply to the USB circuitry. Insufficient or unstable power can cause the USB device to fail to enumerate or disconnect intermittently. This can be checked using a multimeter to measure the voltage levels at various points on the board. It's also important to ensure that the USB data lines have the correct termination resistors, as these resistors are crucial for signal integrity and impedance matching. Incorrect termination can lead to signal reflections and data corruption, preventing the device from communicating properly with the host. Finally, the developer consulted the AT32F405 datasheet and application notes, which provide detailed information about the USB peripheral and its configuration requirements. This is a valuable resource for understanding the intricacies of the microcontroller's USB hardware and the recommended best practices for its use.

The troubleshooting process began with a thorough review of the firmware configuration, focusing on the TinyUSB library settings and the AT32F405's USB peripheral initialization. The developer examined the tusb_config.h file, which is the central configuration file for TinyUSB, to ensure that the USB High-Speed (HS) mode was correctly enabled and that the appropriate USB port was selected. Additionally, the code responsible for initializing the USB PHY (Physical Layer) was carefully inspected. The USB PHY is a crucial component that handles the low-level signaling and data transmission over the USB bus, and its proper configuration is essential for successful USB communication. The developer also verified the clock settings for the USB peripheral. USB HS operation requires a precise 480 MHz clock, and any deviation from this frequency can cause communication failures. The AT32F405 has a complex clock system, and it's essential to ensure that the USB clock is derived from the correct source and that the PLL (Phase-Locked Loop) is configured correctly. Furthermore, the interrupt handlers associated with the USB peripheral were examined to ensure that they were properly configured and that any relevant interrupt flags were being cleared. Interrupts play a vital role in USB communication, as they signal the arrival of data or the occurrence of specific events. If the interrupt handlers are not correctly set up, the device may miss important USB transactions or respond incorrectly. Given the lack of a UART interface for debugging, the developer had to rely heavily on code inspection and a deep understanding of the USB protocol and the TinyUSB library. This underscores the importance of writing clean, well-documented code and having a solid grasp of the underlying hardware and software principles.

Solution

The root cause of the issue was traced to a missing definition in the tusb_mcu.h header file, which is part of the TinyUSB library. Specifically, the TUP_RHPORT_HIGHSPEED macro, which indicates that the USB High-Speed (HS) port is being used, was not defined for the AT32F405. This macro is essential for enabling the HS functionality within the TinyUSB stack. Without it, the library would not properly configure the USB peripheral for HS operation, resulting in the device failing to be recognized by the host. The developer identified this missing definition by carefully reviewing the TinyUSB source code and comparing the configuration settings for the AT32F405 with those of other microcontrollers that support USB HS. Once the missing definition was identified, the solution was straightforward: adding #define TUP_RHPORT_HIGHSPEED 1 to the tusb_mcu.h file, within the conditional block for TU_CHECK_MCU(OPT_MCU_AT32F402_405). This effectively enabled the HS functionality for the AT32F405 within TinyUSB. After making this change, the custom board was successfully recognized by the host computer, and USB HS communication was established. This highlights the importance of thoroughly understanding the software libraries and frameworks being used, as well as the specific configuration requirements of the target microcontroller. It also demonstrates the value of a systematic troubleshooting approach, where each potential point of failure is methodically examined and eliminated.

The solution involved adding a crucial definition to the tusb_mcu.h file within the TinyUSB library. The specific line added was #define TUP_RHPORT_HIGHSPEED 1 within the #elif TU_CHECK_MCU(OPT_MCU_AT32F402_405) block. This definition tells the TinyUSB library that the USB High-Speed (HS) port is being used, which is essential for proper initialization and operation of the USB HS peripheral on the AT32F405. Without this definition, TinyUSB would not correctly configure the USB PHY and other related hardware components, leading to the device failing to enumerate on the host. The reason this definition was missing is likely due to an oversight in the TinyUSB library's configuration for the AT32F405. While the library supported the AT32F405, it appears that the specific configuration for USB HS was not fully implemented. This type of issue is not uncommon in open-source libraries, as they often support a wide range of microcontrollers and configurations, and it's possible for certain combinations to be missed during development and testing. The developer's discovery of this missing definition highlights the importance of carefully reviewing library configurations and understanding the underlying hardware requirements. It also demonstrates the value of community contributions to open-source projects, as the developer's fix can benefit other users of TinyUSB and the AT32F405. After applying this fix, the custom AT32F405 board was successfully recognized by the host computer, and USB HS communication was established. This allowed the developer to proceed with their project and utilize the high-speed data transfer capabilities of the USB HS interface.

#elif TU_CHECK_MCU(OPT_MCU_AT32F402_405)
  #define TUP_USBIP_DWC2
  #define TUP_USBIP_DWC2_AT32
  #define TUP_DCD_ENDPOINT_MAX    8
+ #define TUP_RHPORT_HIGHSPEED    1

This code patch was applied to the tusb_mcu.h file to resolve the issue. The TUP_RHPORT_HIGHSPEED macro is crucial for enabling USB High-Speed functionality in TinyUSB.

Discussion and Implications

While the fix resolved the immediate problem, the developer raised a valid concern about its broader implications. The TUP_RHPORT_HIGHSPEED definition was added within the conditional block for TU_CHECK_MCU(OPT_MCU_AT32F402_405), which covers both the AT32F402 and AT32F405 microcontrollers. However, the AT32F402 does not support USB HS, so enabling this definition for the AT32F402 could potentially lead to unexpected behavior or conflicts. This highlights the importance of considering the impact of a fix on other parts of the system and ensuring that it doesn't introduce new issues. In this case, a more precise solution would be to define TUP_RHPORT_HIGHSPEED specifically for the AT32F405, rather than for the entire family. This could be achieved by adding a separate conditional block for TU_CHECK_MCU(OPT_MCU_AT32F405), or by using a more granular configuration mechanism within TinyUSB. The developer's awareness of this potential issue demonstrates a good understanding of the system and a commitment to ensuring the robustness of the solution. It also underscores the need for thorough testing and validation after applying any fix, to ensure that it functions correctly in all intended scenarios. Furthermore, this situation highlights the challenges of maintaining code that supports multiple hardware platforms, as it requires careful consideration of the specific capabilities and limitations of each platform. Library developers often use conditional compilation and other techniques to manage these differences, but it's still possible for subtle errors to slip through.

The broader implications of this fix highlight the importance of precise configuration and conditional compilation in embedded systems development. The fact that the TUP_RHPORT_HIGHSPEED definition was applied to both the AT32F402 and AT32F405, even though the AT32F402 does not support USB HS, raises concerns about potential side effects. While this fix resolved the USB HS issue on the AT32F405, it may inadvertently introduce problems on the AT32F402, as the system might attempt to initialize and use the USB HS peripheral, even though it's not present. This could lead to unexpected behavior, such as lockups or crashes, or it may simply waste resources by unnecessarily configuring the USB peripheral. A more robust solution would involve using conditional compilation to define TUP_RHPORT_HIGHSPEED only for the AT32F405, ensuring that it does not affect the AT32F402. This could be achieved by adding a separate #ifdef block specifically for the AT32F405, or by using a more sophisticated configuration mechanism within the TinyUSB library. This situation also underscores the importance of thorough testing and validation after applying any fix or change to the system. It's crucial to test the fix not only on the target platform (AT32F405 in this case) but also on other platforms that share the same code base (AT32F402). This helps to ensure that the fix does not introduce regressions or unexpected behavior on other platforms. Furthermore, it highlights the need for clear and accurate documentation of the system's configuration options and dependencies. This makes it easier for developers to understand the system and make informed decisions about configuration changes.

Conclusion

This case study provides a valuable insight into the troubleshooting process for USB High-Speed (HS) issues on the AT32F405 microcontroller. The problem, a failure of the custom board to be recognized by the host, was traced to a missing definition in the TinyUSB library's configuration file. The solution involved adding the TUP_RHPORT_HIGHSPEED macro, which enabled HS functionality within the library. However, the fix also raised concerns about its potential impact on the AT32F402, which does not support USB HS. This underscores the importance of careful consideration of the broader implications of any fix and the need for precise configuration and conditional compilation in embedded systems development. This issue highlights the common challenges faced when working with embedded systems, custom hardware, and open-source libraries. It demonstrates that a systematic approach to troubleshooting, combined with a deep understanding of the hardware and software involved, is essential for resolving complex problems. The lack of a UART interface for debugging in this case further emphasized the need for meticulous code inspection and a strong grasp of the USB protocol and the TinyUSB library. The solution, while effective, also serves as a reminder of the importance of thorough testing and validation after applying any fix, to ensure that it functions correctly across all intended platforms and scenarios. Moreover, the developer's contribution to identifying and resolving this issue underscores the value of community involvement in open-source projects, where collective knowledge and expertise can lead to more robust and reliable software.

In conclusion, this troubleshooting journey demonstrates the complexities and nuances of embedded systems development, particularly when dealing with high-speed communication interfaces like USB HS. The process of identifying the missing TUP_RHPORT_HIGHSPEED definition highlights the need for meticulous attention to detail and a systematic approach to debugging. The developer's initial problem—the custom AT32F405 board not being recognized by the host—is a common frustration, but by carefully examining the firmware configuration and leveraging the TinyUSB library's structure, they were able to pinpoint the root cause. The solution, while seemingly simple, underscores the importance of understanding the underlying hardware and software interactions. The discussion about the broader implications of the fix, specifically the potential impact on the AT32F402, reinforces the critical role of conditional compilation and platform-specific configurations in embedded systems. This ensures that changes intended for one device do not inadvertently affect others. Furthermore, the lack of a UART interface for debugging added a layer of complexity, emphasizing the need for alternative debugging strategies, such as code inspection and a deep understanding of the USB protocol. This experience serves as a valuable lesson for other developers working with the AT32F405, TinyUSB, or similar embedded systems, emphasizing the importance of a systematic approach, thorough testing, and a commitment to understanding the intricacies of the hardware and software.