Re: Duty Cycle
The 253 in my example relates to the duty cycle required...
Assume 8 bit PWM ...the maximum duty cycle (100% ...full on) would be a value of 255 (a value of 0 being the minimum), a 50% duty cycle would be 127 ...and so on.
Therefore for 8 bit pwm a setting of 255 = 100% duty (remember 0 is the first value ...so that all amount to 256 possible values) ...for the purposes of calculation we can call 100% a duty of 1.
So in my earlier example, the duty in place (253) would be a 253th of 256 possible values or ......1/256 * 253 ...which is 98.828125%.
We're not talking 'time' as such here ...but a ratio of on to off.
The problem with a PWM frequency of 38Khz is that - depending on your PIC Clock - you might not be able to use 256 values of PWM (the amount of pwm bits available is inverse to your chosen PWM frequency)...a quick check with Mister E's Pic multicalc (http://www.picbasic.co.uk/forum/show...8308#post78308) shows that at 38.462 KHz and a PIC oscillator setting of 8Mhz, you've actually only 210 bits of pwm available to you ..... therefore for 50% duty, you'd need a duty cycle register value of 105 & so on.
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