I need to maintain the ratio of the two voltages
and I don't know how high they will
get. Milliseconds is OK, but faster is
better. I didn't realize the PRU's could do ADC.
At 11:00 AM 10/30/2015, Przemek Klosowski wrote:
You can't feed more than 1.8V to ADC without
damaging it. You can, however, scale it with a
simple resistor divider (resistor R1 connected
between the ground and second resistor R2,
which is then connected to your signal), and
hook the ADC to the middle of the
divider where it will be scaled down by the
ratio R1/(R1+R2). How quickly do you want the
result? If it's miliseconds, Linux is perfectly
capable of that; if microseconds, then PRUs can
do it; otherwise, you'd have to come with an analog multiplier circuit.
On Fri, Oct 30, 2015 at 7:23 AM, John
<<mailto:ra...@mediacombb.net>ra...@mediacombb.net> wrote:
I'm a hobbyist with a recent BBB and I want to
use a couple of ADC channels in real time
(alternate). As nearly as I can tell, this is
not supported by the two risk units.
Have I missed something?
BBB and Linux are new to me. One of the things
I would like to do is compute a ratio between
two voltages, each of which might exceed 1.8
VDC. One solution might be to use DACs to sent
feedback voltages to operational amplifiers that
are supplied by 1.8 VDC. The goal is to
determine the ratio as quickly as possible and
without waiting for Linux to get around to it (waiting for the ADC to happen).
John
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