[time-nuts] V standards

[Poul-Henning Kamp]

In message <20081203104032.E3F3FBCD7 at ip-64-139-1-69.sjc.megapath.net>, Hal Murr
ay writes:

>> You don't want 24bit PWM, you want to combine a normal DAC with PWM
>> modulation.
>
>> The disadvantage is that the result is not linear.  But it is
>> monotonic and approximately the lower 4/5th of the distinct
>> combinations are practically useful. 
>
>Where is the non linearity coming from?
>
>Why is only the bottom 4/5s useful?

Because the DAC and PWM multiply instead of add:

Run this script and plot the '_f' file:

	#!/bin/sh
	echo | awk '
		{
		for (i = 0; i < 4096; i++) {
			for (j = 0; j < 1024; j++) {
				x = 3.3 * (i / 4096.) * (j / 1024.)
				printf "%12.9f\n", x
			}
		}
		}
	' | sort -u | tee /tmp/_f | wc -l

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