Pulse widith modulation ee 587 presented by viswanadha kakarlapudi
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PULSE WIDITH MODULATION EE 587 Presented by Viswanadha Kakarlapudi PowerPoint PPT Presentation


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PULSE WIDITH MODULATION EE 587 Presented by Viswanadha Kakarlapudi. Overview. Introduction Implementing 16-Bit PWM Using the PCA 16-Bit PWM Using the On-Chip Timer How Servos Work References. Introduction. Signal Information is encoded in the duty cycle

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PULSE WIDITH MODULATION EE 587 Presented by Viswanadha Kakarlapudi

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PULSE WIDITH MODULATIONEE 587Presented byViswanadha Kakarlapudi


Overview

  • Introduction

  • Implementing 16-Bit PWM Using the PCA

  • 16-Bit PWM Using the On-Chip Timer

  • How Servos Work

  • References


Introduction

  • Signal Information is encoded in the duty cycle

  • Input to the PWM implementation is an integer proportional to the duty cycle desired


Implementing PWM Using PCAIntroduction to PCA (Programmable Counter Array)


Implementing PWM Using PCA8-Bit PWM


Implementing PWM Using PCA8-Bit PWM

  • Duty cycle can be changed by single 8-bit write to PCAOCPHn


16-Bit PWM Using the PCA


16-Bit PWM Using the PCA

  • Duty cycle can be changed by single 16-bit write to the variable PWM


16-Bit PWM Using an On-Chip Timer

  • The C8051F2xx family SoC’s feature three on-board timers that can be used for PWM generation

  • The C8051F226-TB features a low-pass filter that can be readily used for the PWM DAC


16-Bit PWM Using an On-Chip Timer

  • Timer is set to the amount of time the PWM wave is high during one cycle

  • When the timer overflows, the program vectors to an ISR to take a port pin high or low to produce the PWM wave

  • The smallest pulse width that can be assigned is 19 clock cycles. The ISR takes 14 cycles to take the PWM wave from high to low


16-Bit PWM Using an On-Chip Timer


How Servos Work

  • Servos are commanded through PWM signals

  • In order for the Servo to hold position, the command must be sent every 20ms


How Servos Work


References

  • www.cygnal.com/appnotes

  • www.brookshiresoftware.com


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