Hi everyone,
I'm writing a really simple app for the 7260 analog to digital converter
based on the sample code provided here:
ftp://oz.embeddedarm.com/ts-arm-sbc/ts-7260-linux/samples/adc_72xx.tar.gz
and I have a couple of questions that some of you may have already answered.
In the file adc_7250.c, there are a couple of numbers that I would
imagine to be slightly irrelevant for a 12-bit ADC in the following
operations:
if(avg < 0x7000)
avg = avg + 0x10000;
Why are they present?
Similarly, I don't really follow where the 'magic numbers' below come from:
avg = avg - 0x9E58;
val = ((double)avg * 3.3) / 0xC350;
The code is taken from lines 177 to 199.
I guess the last question that I have is:
Assuming that the source impedence of whatever signal is being measured
is < 10 Ohms, is the transfer characteristic of the ADC linear? For some
reason, I find it very hard to believe, because the 'steps' for a 5.15V
POWER_IN signal are 420, while for a 12.4 V signal are in the range of
3200 steps.
Has anyone analyzed this characteristic with a reliable variable power
supply?
Cheers,
Chris
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