Hi --
--- In "j.chitte" <> wrote:
>
> Hi,
>
> the sample code in adc_7250.c shows how to control the five ADC
> channels on the std 7250.
>
> Where is the documentation relating to use of the optional extra 8
> channels?
The 8 channels are in the optional MAX197 chip, and the data sheet
is available from Maxim. This data sheet, the TS example code, and
the device driver in the files section of the forum should be plenty
of documentation.
[FYI, your board must be ordered with the MAX197 chip, it cannot be
added after the fact unless the board is reprogrammed by TS.]
>
> also the example following line relating to converting the ADC
input
> data but there is no comment as to why this is needed or the
meaning
> of the 0x7000 test.
>
> if(avg < 0x7000)
> avg = avg + 0x10000;
>
> Neither do I see anything in the Cirrus data sheet that would
explain
> this.
First, this only applies to the 5 built-in A/D channels on the
cirrus chip, not the MAX197.
To see why it's needed, look at the transfer function (digital
output vs. analog input voltage) on p.34 of the EP9302 Data Sheet.
See how the digital output rolls over from 0xFFFF to 0x0000 around
(Vref / 2)? Replot the line, with input voltage on the Y-Axis, and
digital output on the X-axis (0x0 to 0xFFFF), and it's a little
clearer. The 0x10000 is essentially shifting one section of the
curve so the output is a single line not two saw-teeth.
>
> Can anyone shed any light of this?
>
> TIA
>
Regards, ........ Charlie
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