Lecture_11 - PWM & Digital to Analogue conversion

Lecture_11 - PWM & Digital to Analogue conversion -...

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Faculty of Science and Technology Lecture11 PWM & Digital to Analogue conversion SEE215
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Pulse Width modulation (PWM) Pulse Width Modulation is a powerful technique used in electronics. It permits the conversion of digital signals to analogue signals such as DC levels, AC signals, position of shafts & levers (amongst others.) Most modern microcontrollers have PWM peripherals which allow many functions to be performed, which after initialisation requires no further processor intervention. PWM are very sophisticated peripherals, and only very simple applications will be considered in this unit.
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Pulse Width modulation (PWM) A PWM signal has several characteristics AMPLITUDE PERIOD OFF TIME ON TIME
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Pulse Width modulation (PWM) The Pulse Width Modulation signals additionally can be described to have A frequency = 1/PERIOD & A duty cycle = ON TIME/PERIOD x100% AMPLITUDE PERIOD OFF TIME ON TIME The signal amplitude is typically the system supply Voltage IE. Typically +5V
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Pulse Width Modulators The ATMega 128 has a 8 PWM Channels, associated with the Timer/Counter module
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ATMega128 PWM channels Eight PWM channels share pins on 4 PORTB & 3 PORTE pins. Timer 0 PWM - OC0 Timer 1 PWM - OC1A ,OC1B,OC1C Timer 2 PWM - OC2 Timer 3 PWM – OC3A,OC3B,OC3C OC1C & OC2 share a pin on PORTB and together provide special functions.
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PWM channels
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ATMega128 PWM controls. Each PWM channels are controlled by manipulating four registers Timer Control registers A & B TCCRnA & TCCRnB Input Compare register ICRn’s & the Output compare registers. OCRnx’s n = 0,1,2 or 3 & x =A, B or C There are fifteen modes of PWM operations possible. Only Mode 14 will be considered.
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Worked Example Set up a PWM output channel from OC1A , with
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This note was uploaded on 09/27/2009 for the course SEB 323 - S taught by Professor Professor during the Three '09 term at Deakin.

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Lecture_11 - PWM & Digital to Analogue conversion -...

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