[Tinyos-help] Battery Voltage measurement

[Michael Schippling]

The value from ADC7 is what you use in the formula.
The ADC code takes care of interleaving calls to various channels
if you are worried about getting a sensor value from ADC1 (and RSSI
from ADC0 for that matter) "at the same time". There (used to be) a
"Voltage" component for mica's that took care of setting the control
pin. You might have a look for that as well.
MS


fhg07 at c3sl.ufpr.br wrote:
> But from which channel does it read?
> I mean, there are seven ! And I must get a reading from both channel seven
> and channel one, in different events. Do you know how do I do that?
> 
> 
> 
> Thanks,
> Fernando.
> 
>> Hi!
>>
>> On Mon, 20 Oct 2008, fhg07 at c3sl.ufpr.br wrote:
>>
>>> According to "MPR-MIB Users Manual":
>>> "To compute the battery voltage:
>>>   1. Set the BAT_MON processor pin (PA5/AD5) to HI.
>>>   2. Program the application code to measure ADC Channel 7.
>>>   3. Compute battery voltage, Vbatt, from Channel 7?s data by:
>>>      Vbatt = Vref × ADC _ FS ADC _ Count
>>>      where:
>>>      Vbatt = Battery voltage
>>>      ADC_FS = 1024
>>>      Vref = External voltage reference = 1.223 V
>>>      ADC_Count = Data from the ADC measurement of Channel 7"
>>>
>>> (This is for MICA2)
>>>
>>>
>>> But how do I get this ADC_Count? Would that be what VoltageRead of
>>> VoltageC returns? I am not sure about that, but the veracity of this
>>> information is really  important. If anyone can affirm this or correct
>>> me,
>>> please answer.
>> In tinyos-2.x the ADC_Count is what the Read.readDone from VoltageC
>> returns. I attached a program that I use to verify this. When the MicaZ is
>> plugged in the USB the value returned was 405 which corresponds to about
>> 3V which seems reasonable.
>>
>> --
>> Razvan ME
> 
> 
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