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

[Oussama Chougna]

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
<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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