In this article, we will introduce the USB protocol layer. Please see our previous article for information regarding the physical layer and network topology: An Introduction to USB Communication (Part 1). USB is a polled bus where the host initiates all transactions. For the host to receive information from USB devices, it must request it
USB (Universal Serial Bus) is an industry-standard used to specify cables, connectors, and protocols that are used for communication between electronic devices. Advantages: Self-configuring interface, no need for user configuration of speed, data protocol, etc.Capable of supplying power to small auxiliary devicesVarious communication speeds are supportedStandard connectorsError checking increases the communication reliability Limitations: Limited cable
In this article, we will take a look at the software timers in FreeRTOS. A software timer allows a function to be executed at a set time in the future.FreeRTOS - RTOS software timer functionality and features description The function that is executed is referred to as a timer's callback function. The interval between starting
Writing programs that just work would make the development of embedded systems a lot easier. In practice, however, a considerable amount of time is devoted to finding and removing bugs from the code. This process is commonly known as debugging and there is no way of avoiding it. In this article, we will give an
In its classic form, a callback (aka callback function) is a function that is passed as an argument to another function. The function that accepts the callback as an argument is expected to call back on it (execute it) at a certain point in time. The callback mechanism allows a lower-level software layer to call
Unaligned memory access is the access of data with a size of N number of bytes from an address that is not evenly divisible by the number of bytes N. If the address is evenly divisible by N, we have aligned memory access. We can express this as Address/N, where Address is the memory address
To better understand the concept of little-endian and big-endian formats we first have to look at how memory is accessed. The memory space of a microprocessor is expected to be byte-addressable. When a CPU has a 32-bit address bus this means that it can access a total of 232 addresses each with a size of
Real-time operating systems (RTOS) allows us to develop complex embedded systems. By using self-contained tasks (threads) each with their own context we can implement programs with multitasking behavior using a single CPU. Passing information between these tasks (inter-task communication) is an important aspect when designing an embedded application using an RTOS. We can say that
The peripheral access layer is a layer of the firmware that provides access to the registers of a microcontroller's peripheral units. It has to be easy to use, well structured, and efficient. This layer is part of the software packages every microcontroller vendor provides for free with their Software Development Kits (SDK) and Integrated Development
Direct Memory Access (DMA) is a process of transferring data from one memory location to another without the direct involvement of the processor (CPU). The main benefit of using DMA is more efficient data movement in the embedded system. Principle of Operation There are many different types of DMA implementations, some of them for very
