This is the application report from Texas Instruments about distance measurement using ultrasonic and MSP430 microcontroller. The report is provided in PDF file, you may download the application report at the end of this post.

This application report describes a distance-measuring system determined by ultrasonic sound using the MSP430F413 ultralow-power microcontroller. The system transmits a burst of ultrasonic sound waves towards the subject point and after that receives the corresponding echo.

This application is primarily based upon the reflection of sound waves. Sound waves are defined as longitudinal pressure waves in the medium in which they’re travelling. Subjects whose dimensions are greater than the wavelength of the impinging sound waves reflect them; the reflected waves are known as the echo. In the event the speed of sound in the medium is recognized and the time taken for the sound waves to travel the distance from the source towards the subject point and back to the source is measured, the distance from the source to the subject point will be computed accurately.

The devices applied to transmit and receive the ultrasonic sound waves within this application are 40-kHz ceramic ultrasonic transducers. The MSP430 drives the transmitter transducer using a 12-cycle burst of 40-kHz square-wave signal derived from the crystal oscillator, and therefore the receiver transducer receives the echo. The Timer_A in the MSP430 is configured to count the 40-kHz crystal frequency such that the time measurement resolution is 25 µs, that is more than enough for this application. The measurement time base is extremely stable because it is derived from a quartz-crystal oscillator. The echo received by the receiver transducer is boosted by an operational amplifier and the amplified output is fed towards the Comparator_A input. The Comparator_A senses the presence of the echo signal at its input and triggers a capture of Timer_A count value to capture compare register CCR1.

The capture is accomplished exactly at the immediate the echo arrives at the system. The captured count will be the measure of the time taken for the ultrasonic burst to travel the distance from the system to the subject point and back to the system. The distance in inches from the system towards the subject point is computed by the MSP430 implementing this measured time and displayed on a two-digit static LCD. Instantly right after updating the display screen, the MSP430 goes to LPM3 sleep mode to keep electrical power. The Basic Timer1 is programmed to interrupt the MSP430 every 205 milliseconds. The interrupt signal from the Basic Timer1 wakes up the MSP430 to repeat the measurement cycle and update the display screen.

Download the application report of distance measurement using ultrasonic and MSP430 microcontroller
» Download Link 1 (direct download from Texas Instruments)
» Download Link 1 (mirror download)

Arduino Tutorial: Use a Piezo Element to Detect Vibration. This tutorial shows you how to use a Piezo element to detect vibration, in this case, a knock on a door, table, or other solid surface.

A piezo is an electronic device that generates a voltage when it’s physically deformed by a vibration, sound wave, or mechanical strain. Similarly, when you put a voltage across a piezo, it vibrates and creates a tone. Piezos can be used both to play tones and to detect tones.

The sketch reads the piezos output using the analogRead() command, encoding the voltage range from 0 to 5 volts to a numerical range from 0 to 1023 in a process referred to as analog-to-digital conversion, or ADC.

If the sensors output is stronger than a certain threshold, your Arduino will send the string “Knock!” to the computer over the serial port.

Open the serial monitor to see this text.

Hardware Required

• Arduino Board
• (1) Piezo electric disc
• (1) Megohm resistor
• solid surface

Piezos are polarized, meaning that voltage passes through them (or out of them) in a specific direction. Connect the black wire (the lower voltage) to ground and the red wire (the higher voltage) to analog pin 0. Additionally, connect a 1-megohm resistor in parallel to the Piezo element to limit the voltage and current produced by the piezo and to protect the analog input.

It is possible to acquire piezo elements without a plastic housing. These will look like a metallic disc, and are easier to use as input sensors. PIezo sensors work best when firmly pressed against, taped, or glued their sensing surface.

Schematic Diagram:

A Piezo to attached to analog pin 0 with a 1-Megohm resistor

Code

In the code below, the incoming piezo data is compared to a threshold value set by the user. Try raising or lowering this value to increase your sensor’s overall sensitivity.

/* Knock Sensor
This sketch reads a piezo element to detect a knocking sound.
It reads an analog pin and compares the result to a set threshold.
If the result is greater than the threshold, it writes
“knock” to the serial port, and toggles the LED on pin 13.
The circuit:
* + connection of the piezo attached to analog in 0
* – connection of the piezo attached to ground
* 1-megohm resistor attached from analog in 0 to ground

http://www.arduino.cc/en/Tutorial/Knock

created 25 Mar 2007
by David Cuartielles
modified 4 Sep 2010
by Tom Igoe
This example code is in the public domain.
*/
// these constants won’t change:
const int ledPin = 13; // led connected to digital pin 13
const int knockSensor = A0; // the piezo is connected to analog pin 0
const int threshold = 100; // threshold value to decide when the detected sound is a knock
or not
// these variables will change:
int sensorReading = 0; // variable to store the value read from the sensor pin
int ledState = LOW; // variable used to store the last LED status, to toggle the light
void setup() {
pinMode(ledPin, OUTPUT); // declare the ledPin as as OUTPUT
Serial.begin(9600); // use the serial port
}
void loop()
// read the sensor and store it in the variable sensorReading:
sensorReading = analogRead(knockSensor);
// if the sensor reading is greater than the threshold:
if (sensorReading >= threshold) {
// toggle the status of the ledPin:
ledState = !ledState;
// update the LED pin itself:
digitalWrite(ledPin, ledState);
// send the string “Knock!” back to the computer, followed by newline
Serial.println(“Knock!”);
}
delay(100); // delay to avoid overloading the serial port buffer
}

Download the Arduino Tutorial: Use a Piezo Element to Detect Vibration in PDF document:
» Download Link

On the Internet there are many examples of code for AVR-GCC , written using functions and macros that are no longer supported in newer versions of the compiler. To use these examples and understand them with the essence of the ports of the microcontroller, you need to rewrite code or use special macros.

For starters, learn programming AVR microcontrollers, this approach can be difficult. As a result, many go to other compilers and never use a cult which has become for many a development environment WinAVR. Although there is a simple way to solve all the problems and return again rejected by the developers of the functions in AVR-GCC. You can use a specially crafted AVR-GCC myROBOT PATCH for WinAVR .

Before we proceed to the description of the patch, let’s see what kind of function it returns. The latest versions of libraries avr-libc, which is part of the compiler AVR-GCC, uses a WinAVR, more functions are not supported inp , outp , sbi and CBI . Made it to the best interpretation of the source code when it is compiled and determine how to handle the port – how to register or to memory. Support for these functions is not starting from WinAVR-20050214 version. This includes no support for such a popular and convenient for many of the former bit_is_set and bit_is_clear .

Of course, nobody calls using only the “old” functions return the patch is backward-compatible programs on the AVR -GCC. Using the patch, you will not lose the ability to work with the new notation, and only return the use of excluded functions. For example, checking the work of any one found on the Internet example, you can practice by rewriting it with the new syntax.
In conclusion, let us consider some examples of possible replacements.

Please note that _BV () is preferable because in this case, the compiler performs a bitwise shift and inserts the result in the compiled code. This ensures that no time spent during direct execution of code in the microcontroller.
As you can see, the possibilities of syntax in the AVR-GCC wide enough to consider him one of the most convenient and flexible means of programming microcontrollers Atmel AVR.

NanoVM is a open-source implementation of the Java virtual machine. The NanoVM was initially developed to run on the Atmel AVR ATmega8 utilized in the Asuro Robot. It was ported to run on the C’t-Bot and the Nibo-robot and can easily be ported to other AVR-based systems.

The virtual machine uses almost 8 kilobytes of code memory (entire flash in case of ATmega8) and 256 bytes of RAM. Each and every user’s .class are processed by NanoVM’s Converter which transforms it into 1 bytecode file. Unique tools next send this file via serial line into device. For this operation is valuable NanoVM’s bootloader (alternatively you are able to use ISP programmer like: PonyProg) which store this content on-chip EEPROM.

NanoVM is not a full featured Java VM and it will never be.  It will constantly be limited to a tiny subset of the java language along with the regular java libraries plus a few application certain strategies. Furthermore, it really is not meant to replace C as the standard way of programming microcontrollers. It is much less flexible and has a lower performance than C or assembler programs.

The NanoVM is actually a method to present a limited but controllable programming interface to a microcontroller based device. With most of essentially the most hardware specific code being portion of the NanoVM itself, the user can focus on the application itself. If a user is given a device equipped using the NanoVM he is not needed to consider the hardware itself. Moreover, he does not need any target distinct compilers or the like. All he wants is a standard java compiler as well as the NanoVMTool which itself is written in java. Thus, the whole development chain works on any device that has a java compiler and can run java code. Using the hardware abstraction the NanoVM gives, the user doesn’t even have to care about the microcontroller type the target is based on. The very same java compiler as well as the identical NanoVMTool could be used with any NanoVM based program running on any sort of microontroller.

NanoWM documentation and download area: go to this page

This is the project report for cellphone controlled mobile robot by Gaurav A.Khadasane, Tejas  Jethwa, Suraj,  Akshay Sonawale. You may use this document for your robot building project reference.

Detail module used for cellphone controlled mobile robot:

• DTMF Decoder: MT8870/CM8870
• Microcontroller: ATMEGA16
• Motor Driver: L293D
• Actuator: DC Motor 5-6V

Download Cellphone Controlled Mobile Robot Tutorial:
Download Link
Learn how to make mobile robot controlled
by a cellphone

Download the document of step by step Make a Robot tutorial:
Download Link

Go to online page of how to make a robot:
Visit the page

This line follower robot use the following module:

• Proximity sensor: 8 pcs of phototransistors
• Microcontroller: ATMega16
• Motor driver: L298 module
• Programming language: C

Download the document of this line follower robot tutorial HERE

This tutorial created by:
Priyank Patil
Department of Information Technology
K. J. Somaiya College of Engineering
Mumbai, India

By the time you complete the text and projects you will:

• Have an intermediate understanding of the C programming language.
• Have a elementary understanding microcontroller architecture.
• Be able to use the WinAVR and AVR Studio tools to build programs.
• Be able to use C to develop microcontroller functions such as:

- Port Inputs and Outputs
- Read a joystick
- Use timers
- Program a Real Time Clock
- Communicate with PC
- Conduct analog to digital and digital to analog conversions
- Measure temperature, light, and voltage
- Control motors
- Make music
- Control the LCD
- Flash LEDs like crazy

Download ebook C Programming for Microcontrollers
or
Buy C Programming for Microcontrollers book from amazon.com for US$ 49.95

You may see the video here.

This line follower robot is very small and simple. This robot is running fast and follow the line very smoothly.

Mechanics

All mechanical and electrical parts are mounted on a proto board, and it also constitutes the chasis.

The line following robot is upheld in three points of two driving wheels and a free wheel. The driving wheels are made with a 7 mm dia ball bearing and a rubber tire. The free wheel is a 5 mm dia ball bearing attached loosely. To drive driving wheels, two tiny vibration motors that used for cellular phone, pager or any mobile equipment are used. Its shaft is pressed onto the tire with a spring plate, the output torque is transferred to the wheels.

The steearing mechanism is realized in differential drive that steear the robot by difference in rotation speed between the left wheel and the right wheel. It does not require any additional actuator, only controling the wheel speed will do.

Line detector and Photo reflector

To detect a line to be followed, most contestants are using two or more number of poto-reflectors. Its output current that proportional to reflection rate of the floor is converted to voltage with a resister and tested it if the line is detected or not. However the threshold voltage cannot be fixed to any level because optical current by ambent light is added to the output current like the image shown right.

Most photo-detecting modules for industrial use are using modurated light to avoid interference by the ambient light. The detected signal is filtered with a band pass filter and disused signals are filtered out. Therefore only the modurated signal from the light emitter can be detected. Of course the detector must not be saturated by ambient light, this is effective when the detector is working in linear region.

In this project, pulsed light is used to cancel ambient light. This is suitable for arraied sensors that scanned in sequence to avoid interference from next sensor. The microcontroller starts to scan the sensor status, sample an output voltage, turn on LED and sample again the output voltage. The difference between the two samples is the optical current by LED, output voltage by the ambient light is canceled. The other sensors are also scanned the same avobe in sequence.

Line Detection Signal Processing

Right image shows the actual line posisiton vs detected line position in center value of 640. The microcontroller scans six sensors and calcurates the line position by output ratio of two sensors near the line. Thus the line position can be detected lineary with only six sensors. All the sensor outputs are captured as analog value that proportioning to reflection ratio, and the sensitivity have variety between each one of them. In this system, to remove the variations from the outputs, calibration parameters for each sensor can be held into non-volatile memory. This can be done with online mode. The microcontroler enters the online mode when an ISP cable is attached, and it can be controlled with a terminal program in serial format of N81 38.4kbps. S1 command monitors sensor values, and S2 command calibrates variation of sensor gain on the reference surface (white paper). The ATmega8 must be set to 8MHz internal osc.

Tracking Control

The line position is compeared to the center value to be tracked, the position error is processed with Proportional/Integral/Diffence filters to generate steering command. The line folloing robot tracks the line in PID control that the most popular argolithm for servo control.

The proportional term is the commom process in the servo system. It is only a gain amplifire without time dependent process. The differencial term is applied in order to improve the responce to disturbance, and it also compensate phase lag at the controled object. The D term will be required in most case to stabilize tracking motion. The I term is not used in this project from following resons. The I term that boosts DC gain is applied in order to remove left offset error, however, it often decrease servo stability due to its phase lag. The line following operation can ignore such tracking offset so that the I term is not required.

When any line sensing error has occured for a time due to getting out of line or end of line, the motors are stopped and the microcontroller enters sleep state of zero power consumption.
Notes:

• Development diary [Ja]
• Circuit diagram
• Firmware May 23, 2004
• Following motion with only P control
  This is a video file of line following motion with only P control. The servo system oscllated.
• Following motion with P and D controls
  Adding D control could improve the servo stability. The robot follows the line correctly. Therefore the servo parameter must be optimized for mechanical characterristics to improve the tracking stability.

Introduction

C Programming and microcontrollers are two big topics, practically continental in size, and like continents, are easy to get lost in. Combining the two is a little like traipsing from Alaska to Tierra del Fuego. Chances are you’ll get totally lost and if the natives don’t eat you, your infected blisters will make you want to sit and pout. I’ve been down this road so much that I probably have my own personal rut etched in the metaphorical soil, and I can point to all the sharp rocks I’ve stepped on, all the branches that have whacked me in the face, and the bushes from which the predators leapt. If you get the image of a raggedy bum stumbling through the jungle, you’ve got me right. Consider this book a combination roadmap, guidebook, and emergency first aid kit for your journey into this fascinating, but sometimes dangerous world.

I highly recommend that you get the book, ‘The C Programming Language – second edition’ by Kernighan and Ritchie, here after referred to as K&R. Dennis Ritchie, Figure 1, wrote C, and his book is the definitive source on all things C.

Figure 1: Dennis Ritchie, inventor of the C programming language stands next to Ken Thompson, original inventor of Unix, designing the original Unix operating system at Bell Labs on a PDP-11

I have chosen to follow that book’s organization in this book’s structure. The main difference is that their book is machine independent and gives lots of examples based on manipulating text, while this book is machine dependent, specifically based on the AVR microcontroller, and the examples are as microcontroller oriented as I can make them.

Why C?

Back in the dark ages of microprocessors, software development was done exclusively in the specific assembly language of the specific device. These assembly languages were character based ‘mnemonic’ substitutions for the numerical machine language codes. Instead of writing something like: 0×12 0×07 0xA4 0x8F to get the device to load a value into a memory location, you could write something like: MOV 22 MYBUFFER+7. The assembler would translate that statement into the machine language for you. I’ve written code in machine language (as a learning experiment) and believe me when I tell you that assembly language is a major step up in productivity. But a device’s assembly language is tied to the device and the way the device works. They are hard to master, and become obsolete for you the moment you change microcontroller families. They are specific purpose languages that work only on specific microprocessors. C is a general-purpose programming language that can work on any microprocessor that has a C compiler written for it. C abstracts the concepts of what a computer does and provides a text based logical and readable way to get computers to do what computers do. Once you learn C, you can move easily between microcontroller families, write software much faster, and create code that is much easier to understand and maintain.

Why AVR?

As microprocessors evolved, devices increased in complexity with new hardware and new instructions to accomplish new tasks. These microprocessors became known as CISC or Complex Instruction Set Computers. Complex is often an understatement; some of the CISCs that I’ve worked with have mind-numbingly complex instruction sets. Some of the devices have so many instructions that it becomes difficult to figure out the most efficient way to do anything that isn’t built into the hardware.

Then somebody figured that if they designed a very simple core processor that only did a few things but did them very fast and efficiently, they could make a much cheaper and easier to program computer. Thus was born the RISC, Reduced Instruction Set Computers. The downside was that you had to write additional assembly language software to do all the things that the CISC computer had built in. For instance, instead of calling a divide instruction in a CISC device, you would have to do a series of subtractions to accomplish a division using a RISC device. This ‘disadvantage’ was offset by price and speed, and is completely irrelevant when you program with C since the complier generates the assembly code for you.

Although I’ll admit that ‘CISC versus RISC’ and ‘C versus assembly language’ arguments often seem more like religious warfare than logical discourse, I have come to believe that the AVR, a RISC device, programmed in C is the best way to microcontroller salvation (halleluiah brother).

The folks that designed the AVR as a RISC architecture and instruction set while keeping C programming language in mind. In fact they worked with C compiler designers from IAR to help them with the hardware design to help optimize it for C programming.

Since this is an introductory text I won’t go into all the detailed reasons I’ve chosen the AVR, I’ll just state that I have a lot of experience with other microcontrollers such as Intel’s 8051, Motorola’s 68xxxes, Zilog’s Z’s, and Microchip’s PIC’s and I’m done with them (unless adequately paid – hey, I’m no zealot). These devices are all good, but they require expensive development boards, expensive programming boards, and expensive software development tools (don’t believe them about the ‘free’ software, in most cases the ‘free’ is for code size or time limited versions).

The AVR is fast, cheap, in-circuit programmable, and development software can be had for FREE (really free, not crippled or limited in any way). I’ve paid thousands of dollars for development boards, programming boards, and C compilers for the other devices, but never again — I like free. The hardware used in this text, the ATMEL Butterfly Evaluation Board can be modified with a few components to turn it into a decent development system and the Butterfly and needed components can be had for less than $40.00 (See Appendix 1 Project Kits). You can’t get a better development system for 10 times this price and you can pay 100 times this and not get as good.

Download ebook C Programming for Microcontrollers

or

Buy C Programming for Microcontrollers book from amazon.com for US$ 49.95