In message <[EMAIL PROTECTED]>, 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
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED] | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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