On Thu, Nov 8, 2012 at 11:12 AM, Roland Stigge <sti...@antcom.de> wrote: > 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
Alban, I think you should include this measurements on the source code as comments, for future reference. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
