A Guide to Approximations
Most embedded processors don’t know how to compute trig and other complex functions. Programming in C we’re content to call a library routine that does all of the work for us. Unhappily this optimistic approach often fails in real time systems where size, speed and accuracy are all important issues. The compiler’s runtime package is a one-size-fits-all proposition. It gives a reasonable trade-off of speed and precision. But every embedded system is different, with different requirements. In some cases it makes sense to write our own approximation routines. Why?
Consistent Overhead Byte Stuffing
Byte stuffing is a process that transforms a sequence of data bytes that may contain ‘illegal’ or ‘reserved’ values into a potentially longer sequence that contains no occurrences of those values. The extra length is referred to in this paper as the overhead of the algorithm. To date, byte stuffing algorithms, such as those used by SLIP [RFC1055], PPP [RFC1662] and AX.25 [ARRL84], have been designed to incur low average overhead but have made little effort to minimize worst case overhead. Some increasingly popular network devices, however, care more about the worst case. For example, the transmission time for ISM-band packet radio transmitters is strictly limited by FCC regulation. To adhere to this regulation, the practice is to set the maximum packet size artificially low so that no packet, even after worst case overhead, can exceed the transmission time limit. This paper presents a new byte stuffing algorithm, called Consistent Overhead Byte Stuffing (COBS), that tightly bounds the worst case overhead. It guarantees in the worst case to add no more than one byte in 254 to any packet. Furthermore, the algorithm is computationally cheap, and its average overhead is very competitive with that of existing algorithms.
An Introduction to programming an Atmega microcontroller
●2 commentsThis document an introduction into the programming of an Atmega microcontroller. It is separated into the fi rst part guiding like a tutorial for beginners and a second part which is a reference book to the functions provided in the basis. The examples and explanations provided are neither exhaustive nor complete. The only aim of this document is to lower the burden of getting started. Only a basic knowledge in C is required.
Introduction to Embedded Systems
This is the first chapter in the book Embedded Systems Hardware for Software Engineers.
Debugging Serial Buses in Embedded System Designs
Many embedded system designs utilize serial buses such as I2C, SPI , USB, RS-232/422/485/UART, CAN, LIN, FlexRay and I2S/LJ/RJ/TDM. Learn how to quickly and efficiently debug today’s serial buses with the powerful trigger, decode, and search capabilities of the MSO/DPO Series.
Design and Implementation of the lwIP Stack
LwIP is an implementation of the TCP/IP protocol stack. The focus of the lwIP stack is to reduce memory usage and code size, making lwIP suitable for use in small clients with very limited resources such as embedded systems. In order to reduce processing and memory demands, lwIP uses a tailor made API that does not require any data copying. This report describes the design and implementation of lwIP. The algorithms and data struc- tures used both in the protocol implementations and in the sub systems such as the memory and bu®er management systems are described. Also included in this report is a reference manual for the lwIP API and some code examples of using lwIP.
Beginning Microcontrollers with the MSP430 - Tutorial
●13 commentsFrom the Preface: I decided to write this tutorial after seeing many students struggling with the concepts of programming the MSP430 and being unable to realize their applications and projects. This was not because the MSP430 is hard to program. On the contrary, it adopts many advances in computing that has allowed us to get our application running quicker than ever. However, it is sometimes difficult for students to translate the knowledge they acquired when studying programming for more traditional platforms to embedded systems.
Embedded Touchscreen Handbook
I want to add a touchscreen to my embedded product. Where do I start? That question is common nowadays. Most manufacturing companies are seeing the value – maybe the necessity – of touch screen technology. Many of them don’t have a long-term or close association with the technology, yet they expect their embedded engineers to handle the project successfully and on a tight schedule. These engineers often have questions... - How much am I going to have to learn to get the job done? - I’ve heard that LCD suppliers were not like other suppliers. But, how so? - What don’t I know that could shift the project from “exciting” to “doomed.” You have choices: Probably the three major questions that crop up when you need to add an LCD touch screen to your product are these: - Should I use a full-blown, embedded operating system, like Windows CE, CE Linux or QNX? - How much work does it take to develop an in-house LCD system from scratch? - Do I have other options? The answer to the first two questions is a resounding “maybe,” (depending on what you need to accomplish). The answer to the third question is, probably “yes.” In most cases, there is another option. Who should read this? If you are an embedded engineer who is thinking of adding a touch screen to your product, and if: - You need to know what is involved in adding color touch controls to your product. -You need to understand the risks (both known and hidden) involved in LCD technology. - Your main area of expertise is not LCD technology. - You don’t want to re-focus your time to acquire color LCD technology expertise. If you find that any of the statements above voice your concerns, you may find this paper worth reading.
Interrupt handling in an ARM processor
●4 commentsThis document is going to guide you at every step as you sit down to design the interrupt handling in software for an ARM system.
A Multithreaded Real-time Robot for Embedded Design Space Exploration
This thesis introduces an autonomous robot platform for real-time scheduling exper- imentation and benchmark suite to evaluate real-time optimizations and apply modern task scheduling methods. It makes two contributions. First, it presents a reference hardware and software design for a line-following, obstacle-avoiding and maze-solving robot. This robot is based on a small commercially-available product. The software is structured as a multithreaded real- time system for use in evaluating scheduling approaches for cost-sensitive and resource- constrained applications. Second, it provides a detailed design space exploration showing the costs (processor speed and memory) of di erent scheduling approaches (static vs. dynamic and non-preemptive vs. preemptive). It also measures and analyzes each task's timing information and explores the mini- mum microcontroller clock speed under di erent scheduling approaches.
Reed-Solomon Error Correction
[Best paper on Reed-Solomon error correction I have ever read -- and it's from the BBC!] Reed-Solomon error correction has several applications in broadcasting,in particular forming part of the specification for the ETSI digital terrestrial television standard, known as DVB-T. Hardware implementations of coders and decoders for Reed-Solomon error correction are complicated and require some knowledge of the theory of Galois fields on which they are based. This note describes the underlying mathematics and the algorithms used for coding and decoding,with particular emphasis on their realisation in logic circuits. Worked examples are provided to illustrate the processes involved.
Consistent Overhead Byte Stuffing
Byte stuffing is a process that transforms a sequence of data bytes that may contain ‘illegal’ or ‘reserved’ values into a potentially longer sequence that contains no occurrences of those values. The extra length is referred to in this paper as the overhead of the algorithm. To date, byte stuffing algorithms, such as those used by SLIP [RFC1055], PPP [RFC1662] and AX.25 [ARRL84], have been designed to incur low average overhead but have made little effort to minimize worst case overhead. Some increasingly popular network devices, however, care more about the worst case. For example, the transmission time for ISM-band packet radio transmitters is strictly limited by FCC regulation. To adhere to this regulation, the practice is to set the maximum packet size artificially low so that no packet, even after worst case overhead, can exceed the transmission time limit. This paper presents a new byte stuffing algorithm, called Consistent Overhead Byte Stuffing (COBS), that tightly bounds the worst case overhead. It guarantees in the worst case to add no more than one byte in 254 to any packet. Furthermore, the algorithm is computationally cheap, and its average overhead is very competitive with that of existing algorithms.
An Introduction to programming an Atmega microcontroller
●2 commentsThis document an introduction into the programming of an Atmega microcontroller. It is separated into the fi rst part guiding like a tutorial for beginners and a second part which is a reference book to the functions provided in the basis. The examples and explanations provided are neither exhaustive nor complete. The only aim of this document is to lower the burden of getting started. Only a basic knowledge in C is required.
Time in Wireless Embedded System
●1 commentWireless embedded networks have matured beyond academic research as industry now considers the advantages of using wireless sensors. With this growth, reliability and real-time demands increase, thus timing becomes more and more relevant. In this dissertation, we focus on the development of highly stable, low-power clock systems for wireless embedded systems. Wireless embedded networks, due to their wire-free nature, present one of the most extreme power budget design challenges in the field of electronics. Improvements in timing can reduce the energy required to operate an embedded network. However, the more accurate a time source is, the more power it consumes. To comprehensively address the time and power problems in wireless embedded systems, this dissertation studies the exploitation of dual-crystal clock architectures to combat effects of temperature induced frequency error and high power consumption of high-frequency clocks. Combining these architectures with the inherent communication capabilities of wireless embedded systems, this dissertation proposes two new technologies; (1) a new time synchronization service that automatically calibrates a local clock to changes in temperature; (2) a high-low frequency timer that allows a duty-cycled embedded system to achieve ultra low-power sleep, while keeping fine granularity time resolution offered only by high power, high frequency clocks.
Red Hat Linux - The Complete Reference
This book identifies seven major Linux topics: basic setup, environments and applications, the Internet, servers, administration, and network administration. These topics are integrated into the different ways Red Hat presents its distribution: as a desktop workstation, network workstation, server, and development platform
Driving I2C-Bus Signals Over Twisted Pair Cables with PCA9605
The availability of powerful I2C buffers that drive their I/Os on both sides to a nominal ground or ‘zero offset’ logic level allows the removal of noise introduced into one section of a larger bus system. That ‘regeneration’ of clean I2C signals enables building long I2C buses by combining together relatively short bus sections, each say less than 20 meters, using such buffers or multiplexers that contain them. Conventional twisted pair communication cabling with its convenient connectors, and a ‘modular’ I2C system approach, make large system assembly easy. Each drop point or node can be individually selected for bidirectional data communication with the Master just by using normal I2C software addressing. As an example, a system is described for control of LED lighting displays and it is suggested that the power for the LEDs, and the I2C control system, might be economically provided using ‘extra low voltage’ distribution at 48 V using either the control signal cable or similar low cost wiring in a manner similar to that used in ‘Power over the Ethernet’ systems. The simplicity and flexibility of this approach makes it attractive to consider as an alternative to other control systems such as RS-485 or CAN bus.
Lessons in Electric Circuits - Volume III - Semiconductor
●2 commentsThis book covers all of the common semiconductor devices and their principles of operation. However, the true value of this reference is in the fact that it provides key circuits and applications where they come in handy. A few of the devices that are covered in this book are Bipolar junction transistors, diodes, JFETs, thyristors, OPAMPs and FETs. This book will be a good reference in your library that has a clear style of explanation.
Debugging Serial Buses in Embedded System Designs
Many embedded system designs utilize serial buses such as I2C, SPI , USB, RS-232/422/485/UART, CAN, LIN, FlexRay and I2S/LJ/RJ/TDM. Learn how to quickly and efficiently debug today’s serial buses with the powerful trigger, decode, and search capabilities of the MSO/DPO Series.
Embedded Touchscreen Handbook
I want to add a touchscreen to my embedded product. Where do I start? That question is common nowadays. Most manufacturing companies are seeing the value – maybe the necessity – of touch screen technology. Many of them don’t have a long-term or close association with the technology, yet they expect their embedded engineers to handle the project successfully and on a tight schedule. These engineers often have questions... - How much am I going to have to learn to get the job done? - I’ve heard that LCD suppliers were not like other suppliers. But, how so? - What don’t I know that could shift the project from “exciting” to “doomed.” You have choices: Probably the three major questions that crop up when you need to add an LCD touch screen to your product are these: - Should I use a full-blown, embedded operating system, like Windows CE, CE Linux or QNX? - How much work does it take to develop an in-house LCD system from scratch? - Do I have other options? The answer to the first two questions is a resounding “maybe,” (depending on what you need to accomplish). The answer to the third question is, probably “yes.” In most cases, there is another option. Who should read this? If you are an embedded engineer who is thinking of adding a touch screen to your product, and if: - You need to know what is involved in adding color touch controls to your product. -You need to understand the risks (both known and hidden) involved in LCD technology. - Your main area of expertise is not LCD technology. - You don’t want to re-focus your time to acquire color LCD technology expertise. If you find that any of the statements above voice your concerns, you may find this paper worth reading.
A Multithreaded Real-time Robot for Embedded Design Space Exploration
This thesis introduces an autonomous robot platform for real-time scheduling exper- imentation and benchmark suite to evaluate real-time optimizations and apply modern task scheduling methods. It makes two contributions. First, it presents a reference hardware and software design for a line-following, obstacle-avoiding and maze-solving robot. This robot is based on a small commercially-available product. The software is structured as a multithreaded real- time system for use in evaluating scheduling approaches for cost-sensitive and resource- constrained applications. Second, it provides a detailed design space exploration showing the costs (processor speed and memory) of di erent scheduling approaches (static vs. dynamic and non-preemptive vs. preemptive). It also measures and analyzes each task's timing information and explores the mini- mum microcontroller clock speed under di erent scheduling approaches.
