Re: Accessing specific hardware features of mxs-lradc

[Lars-Peter Clausen <lars@metafoo.de>]

On 07/02/2013 05:45 PM, Alexandre Belloni wrote:
> On 02/07/2013 17:21, Lars-Peter Clausen wrote:
>>>>
>>>> I was looking at that yesterday as I had to had a scale for the
>>>> temperature sensors. You'll have to be careful because the maximum
>>>> measured voltage when DIVIDE_BY_TWO is not set is 1.85V and when it is
>>>> set, it becomes VDDIO - 50mv.
>>
>> I had a quick peak at the datasheet and I think that's a typo. VDDIO is 3.3V.
>> This sentence also doesn't make much sense if divide by two would actually
>> lower the range. "For input channels (other than BATT, 5V, or VDDIO) with
>> signals larger than 1.85 V, the divide-by-two option should be set."
>>
> 
> Yeah, what I think they meant is if !DIVIDE_BY_TWO : Vmax = 1.85V else
> Vmax = 3.25V. So it may not be as easy as multiplying hte scale by two.
> I couldn't test it, so I didn't implement it.

Parse error on my side, in the datasheet it is a hyphen not a minus, so I
though the sentence meant that the maximum is 50mV.

I guess it is still a divide by two, but since the max input voltage is 3.3V
you simply can't max out the ADC anymore since the maximum value corresponds to
3.7V

-Lars