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
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Signal Information is ... of time the PWM wave is high during one cycle ... 14 cycles to take the PWM wave from high to low. 16-Bit PWM Using an On ... – PowerPoint PPT presentation
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Title: PULSE WIDITH MODULATION EE 587 Presented by Viswanadha Kakarlapudi
1
PULSE WIDITH MODULATIONEE 587Presented by
Viswanadha Kakarlapudi
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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
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Implementing PWM Using PCA Introduction to PCA
(Programmable Counter Array)
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Implementing PWM Using PCA8-Bit PWM
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Implementing PWM Using PCA8-Bit PWM
- Duty cycle can be changed by single 8-bit write
to PCAOCPHn
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16-Bit PWM Using the PCA
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16-Bit PWM Using the PCA
- Duty cycle can be changed by single 16-bit write
to the variable PWM
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16-Bit PWM Using an On-Chip Timer
- The C8051F2xx family SoCs 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
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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
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16-Bit PWM Using an On-Chip Timer
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How Servos Work
- Servos are commanded through PWM signals
- In order for the Servo to hold position, the
command must be sent every 20ms
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How Servos Work
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References
- www.cygnal.com/appnotes
- www.brookshiresoftware.com
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