November | 2010 | Embedded Lab

Monthly Archives: November 2010

Timers and counters

Posted on November 11, 2010 by R-B 2 comments

Introduction Most microcontrollers are equipped with one or more precision timing systems that can be used to perform a variety of precision timer functions including generating events at specific times, determining the duration between two events, or counting events. Example applications that require generating events include generating an accurate 1 Hz signal in a digital watch, keeping a traffic light green for a specific duration, or communicating bits serially between devices at a specific rate, etc. Theory of operation The main component of such a timing system is a free running binary counter. The counter increments for each incoming timing

Lab 5: Analog-to-digital conversion (ADC)

Posted on November 10, 2010 by R-B 76 comments

Description Analog-to-digital conversion (ADC) is necessary because, while embedded systems deal with digital values, their surroundings typically involve many analog signals such as, temperature, speed, pressure, the output of a microphone, etc. They all need to be converted into digital data before being processed by the microcontroller. Today, we will see how to read an external analog signal using a PIC16F688 microcontroller, and display the conversion output (a digital number) on a LCD. The input analog signal will be a varying voltage between 0-5V derived using a potentiometer. Required Theory The PIC16F688 microcontroller has a built-in 10-bit ADC with eight

Microcontroller based Diode and Bipolar Junction Transistor (BJT) tester

Posted on November 9, 2010 by R-B 32 comments

Introduction Most of the digital multimeters these days have built-in features for testing diodes and sometimes transistors. The purpose of this project is to demonstrate a simple way to construct a testing device for diodes and bipolar junction transitors (BJTs) using a microcontroller. The testing algorithm is based on a simple fact that a working PN junction conducts current in only one direction. A PIC16F688 microcontroller is used in this project that switches the bias voltage across the PN junctions of diode and transistors, and determines if a particular junction is normal, open or short. Theory The logic behind testing

Lab 3: Four bit binary counter

Posted on November 8, 2010 by R-B 5 comments

Description Today’s lab session is about binary counting LEDs. The binary 1 and 0 will be represented by turning LEDs on and off. You will make a 4-bit binary counter (using 4 LEDs) that counts from 0 to 15 (0000-1111 binary). The four LEDs are connected to RC0 through RC3 port pins of PIC16F688 with current limiting resistors (470? each) in series. A push button switch is connected to pin RC4 to provide input for the counter. The counter starts from 0, and increase by 1 every time the button is pressed. When the counter reaches 15 (all LEDs on),

Lab 4: Interfacing a character LCD

Posted on November 7, 2010 by R-B 20 comments

Description HD44780 based LCD displays are very popular among hobbyists because they are cheap and they can display characters. Besides they are very easy to interface with microcontrollers and most of the present day high-level compilers have in-built library routines for them. Today, we will see how to interface an HD44780 based character LCD to a PIC16F688 microcontroller. The interface requires 6 I/O lines of the PIC16F688 microcontroller: 4 data lines and 2 control lines. A blinking test message, “Welcome to Embedded-Lab.com”, will be displayed on the LCD screen. Required Theory All HD44780 based character LCD displays are connected through

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