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PWM. ECE 4437-Embedded Systems Dr. Glover Christopher Ahn & Khoa Van. What is covered and what is not. Cover: Count down mode and basic configuration to get the motor run. Not cover: Count up/down mode Dead band Interrupt Others. LOAD: Determines PWM period based on system clock.

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Pwm

PWM

ECE 4437-Embedded Systems

Dr. Glover

Christopher Ahn & Khoa Van


What is covered and what is not

What is covered and what is not

  • Cover:

    • Count down mode and basic configuration to get the motor run.

  • Not cover:

    • Count up/down mode

    • Dead band

    • Interrupt

    • Others


Pwm

LOAD: Determines PWM period based on system clock

ADown/BDown: determine pulsewidth

COMPA/COMPB: we set the value to get Adown/BDown


Illustration

Illustration

  • Example: System clock is 80[Mhz] (can be reduced).

  • PWM Clock will be:

    • 80[Mhz]/64=1.25[Mhz] (period is 0.8 [us])

  • We want:

    • 2[ms] period. What is the Load value?

  • Answer: LOAD= (2[ms]/0.8[us])-1


Illustration1

Illustration

  • Now we need to generate pulse width,

    • We will generate 20% duty cycle for PWMA for this example

  • HOW?

  • Easy: LOAD is 100%, so 20%*LOAD is the value for COMPA.


Summary of the code

Summary of the Code:

  • Initialize and enable the Clocks

  • Enable the PWM Modules

  • Configure Pin types

  • Set Duty Cycle

  • Enable the gate

  • Enable generators


Coding example

Coding Example


Pwm

Can be found on page 489 in:

spmu298a_TivaWare_Peripheral_Driver_Lib.pdf


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