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PULSE WIDITH MODULATION EE 587 Presented by Viswanadha Kakarlapudi

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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  1. PULSE WIDITH MODULATIONEE 587Presented byViswanadha Kakarlapudi

  2. Overview • Introduction • Implementing 16-Bit PWM Using the PCA • 16-Bit PWM Using the On-Chip Timer • How Servos Work • References

  3. Introduction • Signal Information is encoded in the duty cycle • Input to the PWM implementation is an integer proportional to the duty cycle desired

  4. Implementing PWM Using PCAIntroduction to PCA (Programmable Counter Array)

  5. Implementing PWM Using PCA8-Bit PWM

  6. Implementing PWM Using PCA8-Bit PWM • Duty cycle can be changed by single 8-bit write to PCAOCPHn

  7. 16-Bit PWM Using the PCA

  8. 16-Bit PWM Using the PCA • Duty cycle can be changed by single 16-bit write to the variable PWM

  9. 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

  10. 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

  11. 16-Bit PWM Using an On-Chip Timer

  12. How Servos Work • Servos are commanded through PWM signals • In order for the Servo to hold position, the command must be sent every 20ms

  13. How Servos Work

  14. References • www.cygnal.com/appnotes • www.brookshiresoftware.com

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