The vast majority of computers in use, however, are much less visible. They run the engine, brakes, seatbelts, airbag, and audio system in your car. They digitally encode your voice and construct a radio signal to send it from your cell phone to a base station. They command robots on a factory floor, power generation in a power plant, processes in a chemical plant, and traffic lights in a city. These less visible computers are called embedded systems, and the software they run is called embedded software.
The principal challenges in designing and analyzing embedded systems stem from their interaction with physical processes. This book takes a cyber-physical approach to embedded systems, introducing the engineering concepts underlying embedded systems as a technology and as a subject of study.
The focus is on modeling, design, and analysis of cyber-physical systems, which integrate computation, networking, and physical processes.
The second edition offers two new chapters, several new exercises, and other improvements. The book can be used as a textbook at the advanced undergraduate or introductory graduate level and as a professional reference for practicing engineers and computer scientists. Readers should have some familiarity with machine structures, computer programming, basic discrete mathematics and algorithms, and signals and systems. This book strives to identify and introduce the durable intellectual ideas of embedded systems as a technology and as a subject of study.
The emphasis is on modeling, design, and analysis of cyber-physical systems, which integrate computing, networking, and physical processes. The Newnes Know It All Series takes the best of what our authors have written to create hard-working desk references that will be an engineer's first port of call for key information, design techniques and rules of thumb.
Guaranteed not to gather dust on a shelf! Circuit design using microcontrollers is both a science and an art. This book covers it all. It details all of the essential theory and facts to help an engineer design a robust embedded system.
Our authors bring a wealth of experience and ideas; this is a must-own book for any embedded designer. A thorough introduction to the development and applications of intelligent wearable interfaces As mobile computing, sensing technology, and artificial intelligence become more advanced and their applications more widespread, the area of intelligent wearable interfaces is growing in importance. This emerging form of human-machine interaction has infinite possibilities for enhancing humans' capabilities in communications, actions, monitoring, and control.
Intelligent Wearable Interfaces is a collection of the efforts the authors have made in this area at The Chinese University of Hong Kong. They introduce methodologies to develop a variety of intelligent wearable interfaces and cover practical implementations of systems for real-life applications. A number of novel intelligent wearable interface systems are examined, including: Network architecture for wearable robots Wearable interface for automatic language translation Intelligent cap interface for wheelchair control Intelligent shoes for human-computer interface Fingertip human-computer interface Ubiquitous 3D digital writing instrument Intelligent mobile human airbag system This book is a valuable reference for researchers, designers, engineers, and upper-level undergraduate and graduate students in the fields of human-machine interactions,rehabilitation engineering, robotics, and artificial intelligence.
Using easy-to-find components and equipment, this hands-on guide helps you build a solid foundation in electronics and embedded programming while accomplishing useful--and slightly twisted--projects.
Most of the projects have fascinating visual appeal in the form of large LED-based displays, and others feature a voice playback mechanism. Full source code and circuit files for each project are available for download. The larger workbook-style layout and convenient two-column format make following the step-by-step instructions a breeze.
Make Great Stuff! Most unit conversions involve two parts, a slope or gain and an offset. It depends on the type of conversion to define which part is applied when. The example shows fixed-point arithmetic performed by multiplying the ADC counts by 24, which would make the value have two places after the decimal that is, The barometric pressure and humidity are different in that the scaling occurs before the offset.
This is because the values of the ADC go rail-to-rail 0 to 5 V DC and the offset applies to the units directly instead of the counts. For example, with barometric pressure, the ADC value will be 0 V when the pressure is The result is then offset by or The same processes described hold true for the temperature, humidity, and wind speed measurements delivered by the outdoor unit.
Wind chill and dew point are treated differently in that they are products of a look-up-table. Just as before, if the system is displaying metric values, the converted units are rescaled to metric. The display is an Optrexcompatible device operating in 4-bit mode. This means that all of the data going to the device is transferred using four data lines.
E is used as a strobe to validate the data DB to the display. As mentioned previously, the display maintenance and user interface are all happening at the lowest level. The normal operation of device is not disturbed by the time spent converting and displaying information, but during editing, the real-time clock does not update and other data collection processes are ignored until the user exits the editing process.
As stated earlier, the tests may be as extensive as needed to convince a customer, or they may be as simple as comparing the results to the local weather station. For the purposes of this text, extensive testing is above and beyond the scope of the requirements and would contribute little to expanding your knowledge of project development.
However, one important topic to be addressed here is what to do if the project does not meet specifications, that is, it fails a system test. Problems such as incorrect calibration of the temperature results, lack of linearity in the humidistat, and mismeasurement of the rain gauge will all be spotted during system test.
The important issue is what to do about it, and there are really only two choices: fix it, or change the specification. Changing the specification is only a very last resort and should not be required if the Definition Phase was carried out properly.
So fixing it is the only real choice. As an example, consider the wind speed indicator. Its intended calibration was based on an empirically derived number from the manufacturer 2. We just did not get quite as many pulses per second out of the system as we expected at a wind speed of mph. In this case, even though there is some error, the result is linear, so a simple adjustment of the scaling would be in order.
You can adjust these easily if necessary without looking through the program to find where the constants or calibration factors Theoretical Output Frequency in Hz. Figure 5—34 Example, Measured Anemometer Output are used, and perhaps missing one or two, if they are used in multiple places.
Examination of the program will show that these are inserted in the program and really do not increase or decrease code size by their use, so they are a no-cost convenience.
The choice of method, in this case, greatly depends on the expected accuracy, the precision of the result, and available computing time. As long as there is curve to the earth, gravity pulling us down, and the sun rising every day to cause a constant change in temperature, the data that is collected is going have a shape, and it is probably not going to be a straight line.
One of the best parts of the LUT approach is that you can use the data you actually collected. Table 5—6 shows measured frequencies. With ten frequency measurements from our wind tunnel testing, an array is formed to create the LUT. If the speed is lower than the LUT, it is less than one mph and nothing can be computed. Otherwise, it is not difficult to see the level of accuracy that can be achieved using a method of this type. In this example, we simply throw the fractional portion away.
In this instance, a simple LUT and linear interpolation can be applied effectively to linearize a nonlinear result so that the project will meet its specifications. As shown in the example above, the purpose of the system test is to ensure, to whatever degree necessary, that the system performs to specifications. After the tests are completed and any necessary adjustments made, the project is ready for use with a high degree of confidence in the results. Now that the weather station product is designed and proven stable and reliable, what are the areas that costs could be reduced?
In your career, you may be faced with this question time and time again. There are many areas in our weather station project where cost could be reduced. Items such as the humidity sensor, tipping rain bucket, and anemometer are all pretty expensive—but their performance is known and therefore may not be the first place to starting cutting away at the cost. When we started the development process, we chose a processor that would give us ample room to design and debug the software—but we left ourselves the option to increase or decrease memory and features as required, without involving a large redesign effort.
Looking at other members of the AVR family, we need to select a component with very similar features, but perhaps one with a smaller memory space.
There are very few external connections, so even a smaller pin-count part would be acceptable. The ATMega48 has these features, comes in a pin TQFP package, which is a surface-mount package, so no socket is required and it can be easily assembled by a robot, saving labor costs as well , and has a 4K memory space, so it is more closely matched to our actual application size. That can be significant. Changes to the Schematic Figure 5—35 shows the outdoor unit schematic modified to work with the ATMega These changes can all be made in the initialization function.
Performing two 8-bit accesses and combining them for the bit result can easily overcome this. The TIMER1 counter is stopped during the read to prevent the counter from changing while it is being read, yielding a bogus result. Once the two 8-bit reads are performed, the TIMER1 counter is reenabled and everything continues on as usual.
It is these differences that reinforce the fact that reading the datasheet is a critical step in the development and support of software.
As Atmel finds better ways to do things with AVRs, those features will be incorporated into their parts. So you may have noticed a couple of unique items in the initialization process.
One of the features is a clock prescaler that allows the system clock to be divided down to reduce the power consumption of the processor by running it slower.
In order to guarantee a glitch-free change in the system clock while changing the prescale, it is required that the CLKPR register be enabled and modified within four system clock cycles. This causes the compiler to generate the assignment instructions in-line and to reduce the potential of the optimizer inserting a call or jump instruction between the assignments.
You can see that it is realistic in many cases to move from one processor to another in order to add or reduce features, improve unit cost, improve performance, or reduce power consumption.
In many cases, a move like this can be performed in a few hours with very little impact to the entire design. Allow the user to view them on the display or download them to a PC. The process has been demonstrated by the development of a weather station based on the Atmel Mega16 microcontroller. List each of the steps of the process of project development and give an example of the activities that would take place during that step Section 5.
In which step of the project development process would each of the following occur Section 5. Prototyping a sensor and its conditioning circuitry B. Creating detailed specifications for a project D. Drawing a project schematic E. Testing individual software functions F. Writing software flowcharts G. Testing the final project to its specifications H.
Doing proof-of-concept testing on a questionable circuit P ro j e c t D e vel o p m e n t 3. Using the table data below, write a program to perform a look-up-table and linearinterpolation operation to return a compensated temperature from the ADC reading Section 5.
Some suggested projects are shown below. This project will require controlling the speed and steering as well as sensing the black line. A device composed of the microcontroller and a video camera that can detect simple shapes such as a square, a triangle, or a circle of black paper on a white surface.
A device using motors, sensors, and a cardboard arrow to point to and follow a heat source as it moves about the room. This device would make excellent use of stepper motors. A replacement for a furnace thermostat. A security system for an automobile with sensors to detect doors being opened including the gas tank cover, the trunk, and the hood and that would detect when the vehicle is being moved.
These are routines that accomplish many of the more common tasks that face a C programmer. As with all C functions, you call the library functions from your code by using the function name and either passing values to the function or receiving the values returned by the function.
In order to make use of the functions, the programmer needs to know what parameters the function is expecting to be passed to it and the nature of any values returned from it. This information is made clear by the prototype for the function. There are many library functions available in most C compilers, gathered into groups by function. This grouping avoids having to include a whole host of unneeded function prototypes in every program.
For example, the function prototypes for the group of routines concerned with the standard input and output routines are contained in a header file called stdio. A comprehensive list, grouped by their header file names, is followed by a detailed description and example of each function, in alphabetical order.
The cabs, labs, and fabs functions return the absolute value of the signed char, long, and float variable x as an unsigned char, unsigned long, and float value, respectively. The variable x must be in the range of —1 to 1.
The atoi and atol functions convert the string to an integer or long integer, respectively. All three functions skip leading white space characters.
Valid numeric characters are the digits 0 through 9. The function atof also accepts the decimal point as a valid numeric character. Once a non—white space character is encountered, the conversion to a numeric equivalent starts.
The conversion stops when the first non-numeric character is encountered. If no numeric characters are found, the functions return zero. All three functions return signed values. Enter a signed integer number followed by! In binary coded decimal representation, the upper nibble of the value represents the 10s digit of a decimal value. The lower nibble of the value represents the 1s digit of a decimal value.
Gray codes were developed to prevent noise in systems where analog-to-digital conversions were being performed. Gray codes have the advantage over binary numbers in that only one bit in the code changes between successive numbers. The bin2gray functions bin2grayc, bin2gray, and bin2grayl are tailored for unsigned char, unsigned int, and unsigned long variables, respectively.
Table A—1 lists the Gray codes and their binary and decimal equivalents for values 0 through On return, the function returns a pointer to the start of the memory block which is filled with zeros.
This must be taken into account when specifying the heap size in the Project Configure C Compiler Code Generation menu. Returns: If successful in finding contiguous free memory of the appropriate size, returns a pointer to the memory block. If unsuccessful, returns a null pointer. Initial Values! In other words, the ceil function rounds x up to the next integer value and returns that value.
The angle x is expressed in radians. The actual delay depends on the clock crystal frequency. Therefore, it is important to specify the correct clock frequency.
This can be done either in the Project Configure C Compiler menu or with the statement define xtal xL, where xL is the clock frequency in Hertz. Once this is received , for example , it transmits Thanks! Then after an appropriate pause 2 seconds in our example , the first prompt is again transmitted.
Enter a number between 1 and 5. Then it waits until a number is entered followed by a newline character. Then after an appropriate pause 2 milliseconds in our example , the first prompt is again transmitted. This is a sleep mode and similar to the powerdown function. See powerdown in this appendix for the function use. See the Atmel datasheets for the complete description of this sleep mode as it applies to a particular AVR device. Extended standby sleep mode is not available on all AVR devices.
This is the largest whole number that is less than or equal to x. This is a modulo function specifically designed for float type variables.
After being freed, the memory block is available for new allocation. If ptr is null, then it is ignored. Returns: None See malloc. The power of 2 exponent of x is stored at the location pointed to by expon. If x is 0, the value stored at expon is also 0. The value is represented with the specified number of decimal places. Take care to ensure that the memory allocated for str is large enough to hold the entire value plus a null-terminating character. The value is represented as a mantissa with the specified number of decimal places and an integer power of 10 exponent.
Take care to ensure that the memory allocated for str is large enough to hold the entire value plus a null terminating character. As a result, the function waits indefinitely for a character to be received before returning. If another peripheral is to be used for receiving, the getchar function can be modified accordingly. The source for this function is in the stdio. If you want to replace the standard library getchar with your own version, you must do three things.
First, you must place the new getchar function in the. Second, you must follow the new getchar function with a definition statement telling the compiler to ignore any other getchar functions that it finds. Finally, include the standard library. Only 10 characters are allowed. Then the microprocessor waits for either a newline character or 10 characters to be received by the USART.
The following is transmitted: Hi Jane Doe! The gray2bin functions gray2binc, gray2bin, and gray2binl are tailored for unsigned char, unsigned int, and unsigned long variables, respectively. Table A—1 in the bin2gray function description lists the Gray codes and their binary equivalents for values 0 through As such, the microcontroller can wake up from either internal or external interrupts.
Upon waking up from an interrupt, the MCU executes the interrupt and then continues executing at the instruction following the sleep command called by the idle function. ASCII characters range from 0d to d. Control characters range from 0d to 31d and d. Printable characters are between 32d and d. All characters that are not control characters and not alphanumeric characters are considered to be punctuation characters. Characters such as space, line feed, and horizontal tab are considered white space characters.
Take care to ensure that the memory allocated for str is large enough to hold the entire value plus a termination character. On return, the function returns a pointer to the start of the memory block, which is filled with zeros. Returns: If successful in finding contiguous free memory with size bytes, returns a pointer to the memory block.
For the function memcpy, the dst and src memory blocks must not overlap. If the memory blocks do overlap, use memmove instead of memcpy. Unlike memcpy, the src and dest may overlap when calling memmove. The cmin, lmin, and fmin functions return the minimum of the two signed char, long, and float values as a signed char, long, and float value, respectively.
The fractional part of x is returned as a signed floating point number. The integer part is stored as a floating point number at ipart. Notice that the address of the variable to hold the integer portion, not the variable itself, is passed to modf. Both the integer and the floating point results have the same sign as x. The peekw function reads an unsigned integer value from the SRAM at the address addr. Values can be directly written to the SRAM by using the pokeb and pokew functions.
Returns: None See pokeb, pokew for the code example. The pokew function writes the integer value of data to the SRAM at the address addr. Values can be read from the SRAM by using the peekb and peekw functions. In power-down mode, the external oscillator is stopped, while the external interrupts and the watchdog if enabled continue operating. Only an external reset, a watchdog reset if enabled , or an external level interrupt can wake up the MCU.
Upon waking up from an interrupt, the MCU executes the interrupt and then continues executing at the instruction following the sleep command called by powerdown. I am going to sleep until you bug me! Upon waking up, it continues executing at the instruction following the powerdown. The microprocessor continues to run the while loop until power is removed. This is a sleep mode and very similar to the powerdown function.
Powersave sleep mode is not available on all AVR devices. One of the only books available today that uses the increasingly popular and cost-effective Atmel AVR embedded controller as the platform and application for learning, Embedded C Programming and the Atmel AVR, 2E is the perfect choice for novices. Not yet? Well, you must try it. However, nowadays, many people feel so busy. However, not all people are available to do that. This is why you need an e-book.
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