[Tinyos-help] Regarding Sampling Application

Michael Schippling schip at santafe.edu
Wed Feb 6 09:26:57 PST 2008


What I meant about phase accuracy is that you won't be able to use only
five samples to reconstruct a waveform that maintains any sense of when
the peaks and zero crossings happen relative to the original, nor even
the actual frequency to better than 20% (actually I'm guessing on that
value because I'm too lazy to go read up on sampling theory). If your
system doesn't care about such trivia then you're golden.

MS

Coalton Bennett wrote:
> Mr. Schippling, 
>                           Thanks for your reply. I am going to look into 
> the sensing apps on the TInyOS website. You mentioned not being able to 
> reconstruct the waveform with a decent phase. I am not quite sure what 
> you mean by that. I am essentially looking at the waveform generated by 
> a space heater which is a simple resistive load with a perfect 
> sinusoidal current waveform. So I wasn't quite sure what you meant by 
> the phase comment. 
> 
> C.B.
> 
> 
> 
> On Jan 25, 2008, at 2:24 PM, Michael Schippling wrote:
> 
>> Continue reading through the tutorial and all should become clear...hah...
>>
>> The Oscilloscope program does something like what you want, as do the
>> Sense* demo apps in T1. If you are just using an ADC you don't need the
>> whole MDA300 board because the conversion is done directly by the ATMEGA
>> chip itself. In any case without heroic effort (High Frequency Sampling)
>> one can do about 300 conversions per second in the O'scope model, and
>> send about that many over the mica2 radio (the micaz radio will do
>> something like 10x that). That's enough to get a sketchy picture of
>> your 60Hz signal, but you will not be able to reconstruct the full
>> waveform with any decent phase accuracy.
>>
>> MS
>>
>> Coalton Bennett wrote:
>>> Hello TinyOs Programmers,
>>>     I have a quick coding question. I am using the MDA300CA data 
>>> acquisition board that I have coupled to a mote which is sampling a 
>>> voltage which is between the designated ranges for the ADC onboard 
>>> the MDA300CA. I will use one of the seven designated ADC channels 
>>> [0-6] to sample the signal.
>>>     A few words about the signal that I am sampling. It is a 60Hz 
>>> signal with an amplitude within the designated range as specified by 
>>> the instructions manual for the MDA300CA. Given that information, I 
>>> wanted to know two things. Could anyone make any recommendations 
>>> about what the code should be? Or has anyone worked on something 
>>> similar? If so would you be able to provide some ideas about how to 
>>> write the code. (I am not even a novice in TinyOS so I am still 
>>> trying to learn from tutorials). The second question that I have is 
>>> regarding the speed of the sampler. I need to ensure that the 
>>> sampling rate is fast enough so that I have enough samples for 
>>> reconstruction of the waveform at the base station(PC). However it is 
>>> not a requisite for the mote which is sampling the wave form to send 
>>> the data as soon as it is sampled. I plan on using a buffer. Time is 
>>> important but a few seconds of delay is quite alright. My application 
>>> doesn't require real time data in the sense that the delay can't be 
>>> any longer than 10 seconds or so. So a buffer is quite alright. If 
>>> anyone has any ideas of old pieces of code that they think could be 
>>> modified to work with my application I would greatly appreciate it.
>>> C.B._______________________________________________
>>> Tinyos-help mailing list
>>> Tinyos-help at millennium.berkeley.edu 
>>> <mailto:Tinyos-help at millennium.berkeley.edu>
>>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
>>
>> -- 
>> Platform: WinXP/Cygwin
>> TinyOS version: 1.x, Boomerang
>> Programmer: MIB510
>> Device(s): Mica2, MicaZ, Tmote
>> Sensor board: homebrew
>>
> 

-- 
Platform: WinXP/Cygwin
TinyOS version: 1.x, Boomerang
Programmer: MIB510
Device(s): Mica2, MicaZ, Tmote
Sensor board: homebrew



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