[Tinyos-help] can Tmote sky ADC port be used to measure negativevoltage

[Robert Szewczyk]

I think the best way to interface your sensor would be to ground it to
a virtual ground; we've had good experiences using the TLE2426 to
provide virtual ground.

Cheers,

Rob

On 5/1/07, Cory Sharp <cory at moteiv.com> wrote:
> If you read in the MSP430x161x data sheet, in the section "12-bit ADC,
> external reference", the minimum allowable voltage into VeREF- is 0V.
>
> Cheers,
> Cory
>
>
> On 5/1/07, Oussama Chougna <o.chougna at phi-i.com> wrote:
> >
> >
> >
> >
> > Antonio,
> >
> >
> >
> > The settings for an ADC port are defined in MSP430ADC12.h header file.
> >
> > As the negative reference voltage you can specify VeRef-, but in the TMote
> Sky datasheet schematics you can clearly see that the VeRef- pin of the
> MSP430 is soldered to ground.
> >
> > It is moteiv's design and too bad.
> >
> >
> >
> > So programming will take no effect on this.
> >
> >
> >
> > Ground stays zero, so you cannot do conversions between -2,5V and 2,5V.
> But you can between 0 and 2,5V.
> >
> >
> >
> >
> >
> > Greeting,
> >
> >
> >
> >
> >
> > oussama
> >
> >
> >
> > ________________________________
>
> >
> > From: Juan Antonio López Riquelme [mailto:ja.lopez.riquelme at gmail.com]
> > Sent: dinsdag 1 mei 2007 13:16
> > To: Oussama Chougna
> > Cc: yicheng; tinyos-help at millennium.berkeley.edu
> > Subject: Re: [Tinyos-help] can Tmote sky ADC port be used to measure
> negativevoltage
> >
> >
> >
> >
> >
> > Hi Yicheng and Oussama,
> >
> >
> > if you read TEP101 (appendix A) then you can know that the conversion
> reference is programable.
> >
> >
> >
> >
> >
> > For use ADC i supose that you use a components in the folder
> C:\cygwin\opt\tinyos-2.x\tos\chips\msp430\sensors of template and modify the
> fields of struct for use an ADC of expansion port.
> >
> >
> >
> >
> >
> > You also can change values of fields two (sref) and three (ref2_5v) with
> the options that appear below in the same file
> (C:\cygwin\opt\tinyos-2.x\tos\chips\msp430\adc12\Msp430Adc12.h
> ).
> >
> >
> >
> >
> >
> > A greeting,
> >
> >
> > Juan Antonio.
> >
> >
> >
> >
> >
> >
> >
> > 2007/5/1, Oussama Chougna <o.chougna at phi-i.com >:
> >
> >
> >
> > Hi,
> >
> >
> >
> > I have this problem too.
> >
> > If you check the schematics in the TMote Sky datasheet, you will see that
> the negative reference voltage pin is grounded.
> >
> > So you can measure only between 0 and any value.
> >
> >
> >
> >
> >
> > oussama
> >
> >
> >
> > ________________________________
>
> >
> > From: tinyos-help-bounces at Millennium.Berkeley.EDU
> [mailto: tinyos-help-bounces at Millennium.Berkeley.EDU] On
> Behalf Of yicheng
> > Sent: woensdag 25 april 2007 20:53
> > To: tinyos-help at Millennium.Berkeley.EDU
> > Subject: [Tinyos-help] can Tmote sky ADC port be used to measure
> negativevoltage
> >
> >
> >
> >
> > Hi,
> >
> >
> >
> > Just want to know if negative voltage (like -1.5v) can be measured by any
> Tmote sky ADC port? If yes, how can I do it? Do I need to set a negative
> reference voltage?
> >
> >
> >
> > Thanks!
> >
> > Yicheng
> >
> >
> > _______________________________________________
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> > Tinyos-help at Millennium.Berkeley.EDU
> >
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> >
> >
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>
>
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