Friday, December 07, 2007

Peripheral Component Interconnect

The Peripheral Component Interconnect, or PCI Standard (in practice almost always shortened to PCI), specifies a computer bus for attaching peripheral devices to a computer motherboard.The PCI Bus is a high performance bus for interconnecting chips, expansion boards, and processor/memory subsystems.

Wednesday, December 05, 2007

Non-Return-to-Zero Inverted

NRZI encoding is used for data transmission in the standard USB.

EIA standards :RS232/422/485

RS 232,422,485 -quick reference

RS 232 tutorial - A very informative webpage - Recommended

Selecting and Using RS-232, RS-422, and RS-485 Serial Data Standards
An application note from Maxim semiconductors.Includes connection firures for RS232.422,485 and specifications

Dallas Semiconductor application note on RS232
- simple

RS422/485 application note

Comparing Bus Solutions

Texas Instruments Application Report "Comparing Bus Solutions" February 2004, Texas Instruments,

Sunday, December 02, 2007

USB On-The-Go

Every USB communications is between a host and a device. Devices can't communicate with each other directly. The On-The-Go supplement to the USB specification defines a new type of device that can function as both a device and as a scaled-back host (but not both at the same time). When functioning as a device, the On-The-Go device can communicate with a PC or other USB host. When functioning as a host, the device can connect to USB peripherals.

Universal Serial Bus

Tuesday, November 27, 2007

Switch debouncing

Switches can do some really odd things. Most engineers learn this dirty little secret soon after connecting a switch or a relay to a digital system. Switches don't make and break cleanly on the time scales of digital systems. Instead, a typical switch makes multiple transitions during the tens of milliseconds required to open or close, due to effects that include age, operating inertia, mechanical design, and the microscopic condition of the switch-contact surfaces. Commonly called "switch bounce," this behavior is an inescapable fact of life.

- application note 287
:Switch Bounce and Other Dirty Little Secrets,Maxim semiconductors

some resources--

Monday, November 26, 2007

Sunday, November 25, 2007

a round up of microcontroller interfacing techniques

Micro-controllers are useful to the extent that they communicate with other devices, such as sensors, motors, switches, keypads, displays, memory and even other micro-controllers.Many interface methods have been developed over the years to solve the complex problem of balancing circuit design criteria such as features, cost, size, weight, power consumption,reliability, availability, manufacturability.

The following document is a summary of some of these interfacing techniques

Sorting algorithm animation

Sorting algorithms:
We all know that Quicksort is one of the fastest algorithms for sorting. It's not often, however, that we get a chance to see exactly how fast Quicksort really is. The following link will lead you to applets chart the progress of several common sorting algorithms namely Bubblesort , Insertionsort , Quicksort and Select sort

sorting algorithm animation

wiki wiki ??

Wiki Wiki is a reduplication of wiki, a Hawaiian-language word for fast. The word "wiki" (/wiːkiː wiːkiː/) is a shorter form of wiki wiki. WikiWikiWeb was the first site to be called a wiki., Ward Cunningham started developing WikiWikiWeb in 1994, and installed it on Internet domain on March 25, 1995. It was named by Cunningham, who remembered a Honolulu International Airport counter employee telling him to take the so-called "Wiki Wiki" Chance RT-52 shuttle bus line that runs between the airport's terminals. According to Cunningham, "I chose wiki-wiki as an alliterative substitute for 'quick' and thereby avoided naming this stuff quick-web."

I2C Bus

Almost 20 years ago the I2C bus was designed by Philips to allow easy communication between c omponents which reside on the same circuit board. Philips Semiconductors migrated to NXP in 2006.

The name I2C translates into "Inter IC". The original communication speed was defined with a maximum of 100 kbit per second and many applications don't require faster transmissions. For those that do there is a 400 kbit and - since 1998 - a high speed 3.4 Mbit option available.

Meanwhile I2C is not only used on single boards, but also to connect components which are linked via cable. Simplicity and flexibility are key characteristics that make this bus especially attractive for consumer and automotive electronics.

to know more about I2C Bus---

The I2C-Bus and how to use it is a well-known document from Philips discussing the use of this bus in applications.

Wiki article on I2C bus

Reed Relays

As a relay is a switch controlled by an electromagnet, so a reed relay is one or more reed switches controlled by an electromagnet. The contacts are of magnetic material; thus the electromagnet acts directly on them rather than requiring an armature to move them. Sealed in a long, narrow glass tube, the contacts are protected from corrosion, thus are ordinarily plated with silver rather than precious metals. The most common reed relays of the late 1930s through the 80s had two reed switches inserted into holes in the bobbin. Since the moving parts are small, reed relays are capable of faster switching than most others.

Reed Switches (wiki)

Reed Relay Applications

Sunday, November 18, 2007

some interesting motor applications

A document discussing some interesting applications of various types of motors

stepper motor basics

A stepper motor is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps, for example, 200 steps. When commutated electronically, the motor's position can be controlled precisely, without any feedback mechanism (see open loop control)

Some web resources on Stepper Motors:

Stepper motor Basics
Control of Stepping Motors - A Tutorial
A Wiki article on Stepper motors
Nice Animation of a stepping Motor : A German webpage.Please use the slider labelled as continuous to vary speed and run the animation.The stepping modes can also be changed.The type of winding can be selected from the top left corner of the animation

the microsoft way.............

"Microsoft programs are generally bug-free. If you visit the Microsoft hotline, you'll literally have to wait weeks if not months until someone calls in with a bug in one of our programs. 99.99% of calls turn out to be user mistakes. I know not a single less irrelevant reason for an update than bugfixes. The reasons for updates are to present more new features."
-- Bill Gates on code stability, from Focus Magazine

DAC 0808 datasheet

ADC 0804 datasheet

Sunday, November 11, 2007

Understanding DC Electrical Characteristics of Microcontrollers

For the inexperienced designer, understanding the electrical characteristics presented in an integrated circuit data sheet can be confusing. If misinterpreted, a new design could prove disastrous. This tutorial is intended to demystify the steady state characteristics of the Maxim microcontroller product family.(but surely relevant for any microcontroller data sheet)

Friday, November 09, 2007

is 8051 a RISC or a CISC processor?

8051 is a CISC () processor

"CISC (complex Instruction Set Computer), with all the possible adressing modes on the instructions"

although the actual number of instructions is quite small!

So, taking the words at face-value, it is quite "simple" relative to something "complex" like a Pentium;
It is also quite "simple" relative to something like the ARM - which is RISC!

"CISC" and "RISC" have to do with design philosophy rather than raw counts of numbers of instructions...

see the following discussion forum for more

C v/s Assembly

What are the merits and demerits of using C over assembly language for microcontroller programming,just see this discussion

Wednesday, November 07, 2007

Sunday, November 04, 2007

Keil C compiler online manual

von Neumann architecture and Harvard architecture

The von Neumann architecture is a computer design model that uses a processing unit and a single separate storage structure to hold both instructions and data. It is named after mathematician and early computer scientist John von Neumann. Such a computer implements a universal Turing machine, and the common "referential model" of specifying sequential architectures, in contrast with parallel architectures. The term "stored-program computer" is generally used to mean a computer of this design, although as modern computers are usually of this type, the term has fallen into disuse.

Harvard architecture is a computer architecture with physically separate storage and signal pathways for instructions and data. The term originated from the Harvard Mark I relay-based computer, which stored instructions on punched tape (24 bits wide) and data in electro-mechanical counters (23 digits wide). These early machines had limited data storage, entirely contained within the data processing unit, and provided no access to the instruction storage as data, making loading and modifying programs an entirely offline process.

The following link also provides some insight into the topic especially wrt ARM cores

8051 interfacing basics

some websites on 8051 interfacing:

Sunday, January 14, 2007

Cross compiler

A cross compiler is a compiler capable of creating executable code for a platform other than the one on which the cross compiler is run. Such a tool is handy when you want to compile code for a platform that you don't have access to, or because it is inconvenient or impossible to compile on that platform (as is the case with embedded systems, on which various kinds of microcontrollers run with a minimal amount of memory for their own purpose).

Know more about cross compilers from this wiki article

Friday, January 05, 2007

DS1302 - Trickle-Charge Timekeeping Chip

DS1302 - Trickle-Charge Timekeeping Chip

The DS1302 trickle-charge timekeeping chip contains a real-time clock/calendar and 31 bytes of static RAM. It communicates with a microprocessor via a simple serial interface. The real-time clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with an AM/PM indicator.

DS1302 Datasheet

Supervisory Circuits Keep Your Microprocessor Under Control

Maxim Semiconductor - APPLICATION NOTE 279

Supervisory Circuits Keep Your Microprocessor Under Control
Understand the value of a µP supervisor to ensure proper system operation during power-up, power-down, and brownout situations (undervoltage monitoring). In addition, provides information about overvoltage and windowed monitoring. Describes additional features such as manual reset, watchdog timer, battery backup, and chip enable gating. Discusses the need for multi-voltage monitoring.

Maxim Semiconductor - APPLICATION NOTE 279

Advantages of Using a MicroMonitor and a Simple Application Demonstrating the Use of a DS1232

Maxim Semiconductor - APPLICATION NOTE 581

Advantages of Using a MicroMonitor and a Simple Application Demonstrating the Use of a DS1232
Discusses how the DS1232 can be used to MicroMonitor an 8051-based system. This supervisor circuit provides power-on-reset (POR), manual reset (push-button) input, a watchdog timer (strobe timer), and an early power-fail comparator. The reset threshold tolerance can set selected to monitor both 5% and 10% supply tolerance systems. In addition, a pin-selectable reset time-out delay is available.

To simplify the use of the device, a software execution program is included to show how the 8051 processor can be used in conjunction with the DS1232.
Maxim Semiconductor - APPLICATION NOTE 581