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TI Home » TI E2E Community » Support Forums » Microcontrollers » Stellaris® ARM® Microcontrollers » Stellaris® ARM® LM3S Microcontrollers Forum » initialize pwm frequency
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initialize pwm frequency

initialize pwm frequency

This question is not answered
manisha kodag
Posted by manisha kodag
on Jun 21 2012 09:56 AM
Intellectual570 points

with me kit lm3s6965 board.

i read io.c file in that one line is

Intialize the PWM frequency and duty cycle.
   
    g_ulFrequency = 440;
    g_ulDutyCycle = 50;

what is unit of frequency?why this==440?

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  • slandrum
    Posted by slandrum
    on Jun 21 2012 14:37 PM
    Mastermind9640 points

    I'm guessing that 440Hz is chosen because it's the frequency that's the basis for tuning musical instruments.

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  • manisha kodag
    Posted by manisha kodag
    on Jun 22 2012 09:25 AM
    Intellectual570 points

    thank you,

    i have one doubt regarding to the program of obtaining the inter temp of processor,using the ADC.

    In that program i have no any idea how this formula comes?

    ulTemp_ValueC = (((1475 * 1023) - (2250 *  ulADC0_Value[0])) / 10230)


    Once again thanks for your quick reply.

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  • Christian Jolivet
    Posted by Christian Jolivet
    on Jun 26 2012 16:10 PM
    Expert5380 points

    The formula you are referring to was derived from the conversion formula below (which can be found in the datasheet):

    SENSO = 2.7 - ((T + 55) / 75)

    Here "SENSO" is the output voltage of the internal temperature sensor, and "T" is the actual temperature reading.  Given that the internal reference of the ADC is 3.0 V, and a full scale reading corresponds to an ADC output of 1023, you can use the formula from the example code to convert ADC sample values directly to temperatures.

    Regards,

    Christian

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