[sdiy] while we're talking about scaling & biasing etc

[Tom Wiltshire]

On 24 May 2009, at 12:38, Ingo Debus wrote:

>
> Am 24.05.2009 um 05:48 schrieb Jerry Gray-Eskue:
>
>> 1 The Micro you are using has an analog input mux and it is  
>> looking at
>> different pin.
>> 2 The D2A is not setup correctly and so is not reading the voltage  
>> on the
>> pin. This setup can be tricky with a number of registers and bit  
>> flags
>> involved.
>> 3 The Port Pin you are using has not been configured as an analog  
>> input.
>> 4 You are setup for an External Reference and this reference  
>> voltage is
>> missing.
>
> But then it wouldn't work with a known good DC voltage source  
> either. As I understand it, Jason has checked this and it worked  
> ("a pot from 5v").

He didn't say that exactly. He actually said he'd checked the scale- 
and-offset hardware by testing it with a pot from +5V, and that the  
hardware was fine.

You're dead right though, Ingo: the important test to do is to check  
the ADC with the simplest-possible hardware, usually a pot between  
+5V and 0V.

If the ADC works like this, then it's probably something to do with  
the extra hardware. If it doesn't, you've identified it as a software  
problem.

Regards,
Tom