Hardware Debugging: an Overview of Modern Approaches

Abstract

The ubiquity of complex devices built on systems on chip (SoC) with multiple processor cores poses new challenges for developers of embedded systems. New development tools specifically designed for complex systems on chip can help solve them, but these tools are usually limited by the functionality of debugging support tools. High-quality debugging support with advanced features is necessary to take full advantage of complex SoC devices while reducing development time. The article discusses various mechanisms and ways to implement support for debugging systems on chip designed for complex real-time systems used, for example, in the Internet of Things (IoT) paradigm. This review includes an assessment of the available solutions and their suitability for use with the next generation of complex systems on chip with multiple processor cores. It is shown that many existing solutions do not allow developers to easily take advantage of complex functions integrated into the next-generation SoC. The basic debugging support functions for multicore SoCs are summarized and discussed. Recommendations are given for SoC develo­pers and for the future direction of research in this area in order to provide a more suitable basis for new development tools. Such tools are extremely necessary for all embedded hard real-time systems and are of high importance for minimizing the complexity of their development. Modern systems and devices implementing the Internet of Things paradigm are increasingly required to have sufficiently high real-time performance while maintaining low power consumption. These requirements lead to the cre­ation of multicore SoC solutions with support for a wide range of peripheral devices and communication protocols. The systems are limited by the requirements for working in harsh conditions, such as, for example, in the engine compart­ment of a car or on a radar tower. The development of embedded hard real-time systems, in which a task that fails to be completed on time can lead to physical damage of the device, is a complex process. Effective tools, such as interactive debuggers and profilers, are an integral part of solving these problems and are vital for developing reliable embedded systems. Modern technologies now allow the integration of the entire system on a single silicon chip, known as a system on a chip (SoC), which leads to the relocation of existing external interfaces, widely used for development purposes, to the chip. Traditionally, communication within an embedded system is carried out using an external processor system bus, which is implemented in the form of tracks on a printed circuit board. The printed circuit board must support the appropriate interfaces of development tools that require a physical connection, such as, for example, logic analyzers and oscilloscopes. Previously, placing exter­nal interfaces on a chip left fewer options for external analysis tools and, in fact, makes developers "blind" to the internal state of the SoC. Without a reliable and consistent representation of the state of the embedded system, the detection of defects or errors in the system may become difficult or even impossible. The main solution to the problem of the lack of external interfaces is to provide access to internal nodes from outside the system through existing interfaces. There are many different approaches to achieving the required visibility, and they are outlined in this review.