Re: [PATCH] pwm: lpc32xx - Fix the PWM polarity

[Roland Stigge]

On 08/11/12 12:23, Alban Bedel wrote:
>>> It is intended, the formular for duty value in the register is:
>>>
>>> duty = (256 - 256*duty_ns/period_ns) % 256
>>
>> Where does this modulo defined? In the Manual, there is sth. like this
>> defined for RELOADV (tables 606+607), but not for DUTY.
>>
>> Maybe I missed sth. in the manual. Link or hint appreciated!
> 
> The manual doesn't mention this explicitly but you can see that without
> the modulo when duty_ns==0 DUTY would be 256, but the register is only
> 8 bits wide (ie. modulo 256). I made a few test and looked at the PWM
> output on a scope they confirm this:
> 
>  DUTY     HIGH LEVEL
>   1         99.9%
>   25        90.0%
>   128       50.0%
>   220       10.0%
>   255        0.1%
>   0          0.0%
> 
> I'll resubmit the patch with the clamping in the correct order.

Thanks for measuring. With this, your resubmitted patch make much more
sense now.

Roland
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