8-bit Microcontrollers中的主题 Re: How modify LED brightness intensity using PWM?

How modify LED brightness intensity using PWM?

alancalonico — Fri, 07 Mar 2014 18:07:36 GMT

Dear all

My homework for today is vary the LED brightness intensity using PWM. I understand as function PWM talking about duty, will be duty the time than can be in high status. but I don't understand which methods of codewarrior can I use to vary this brightness, could you help me?

i'm using a MCU MC9S8SH8 and CodeWarrior for MCU Version: 10.1

best regards

Re: How modify LED brightness intensity using PWM?

Robinwithu — Thu, 13 Mar 2014 15:03:52 GMT

Hello Alan,

Here is code for generating PWM on your PORTB all pins.

// Define Variables

unsigned char pulse = 0; // Pulse starts at zero, and lengthens

unsigned char duty = 15; // Duty cycle

unsigned char freq = 255; // Frequency

void main() // Main

{

PTBDD_PTBDD = 1; // Define Port B as output port

while( 1 ) // Loop forever...

{

PTBD_PTBD = 1; // Start pulse

for(pulse = 0; pulse < duty; pulse++); // Lengthen pulse if < duty

PTBD_PTBD = 0; // End pulse

for(pulse = 0; pulse < (freq - duty); pulse++); // Continue until frequency

duty++; // Increment Duty cycle

}

Thanks and regards,

Robin

Re: How modify LED brightness intensity using PWM?

alancalonico — Thu, 13 Mar 2014 15:48:59 GMT

Thanks for your answer Robin, fortunately I can resolve with easy method explain following

First divide your amount of brightness step between 0xFF. i.e., if you want 8 steps divide 255/7 and you have next frame

byte frame[8]={0x00, 0x24, 0x48, 0x6c, 0x90, 0xb4, 0xd8, 0xff};

byte counter, error;

for(counter=0, counter<8; counter++)

{

error=PWM_SetRatio8(frame[counter]);

}

well, just need use PWM_SetRatio8(frame[counter]); to change the brightness intensity

Re: How modify LED brightness intensity using PWM?

Robinwithu — Thu, 13 Mar 2014 18:52:13 GMT

Thanks n Regards,

Robin