[Tinyos-help] Pulse detection in T2 TMote port

[André Miguel de Almeida Marrão Rodrigues]

Hi

I will try to find another high resolution timer or the capture. Indeed 
because
of the low resolution of the timer I campared with < and > operators and 
some tolerance.

I can't do much about the noise (grounding is ok, but there is no shielding) 
and the signal has only a 1K resistor in serie,
so it should be enougth for the MSP430 ports.

And yes, you are right 2000 instructions is a lot including the OS code.

Thanks,

André Rodrigues

----- Original Message ----- 
From: "Michael Schippling" <schip at santafe.edu>
To: "André Miguel de Almeida Marrão Rodrigues" 
<andremiguelrodrigues at gmail.com>
Cc: <tinyos-help at Millennium.Berkeley.EDU>
Sent: Thursday, November 22, 2007 6:27 PM
Subject: Re: [Tinyos-help] Pulse detection in T2 TMote port


>
> You probably have two problems. The first one is interference
> from the WiFi signal which may be due to poor grounding/shielding
> or using too low a signal at your input pin. The second is that
> it's fairly dicy trying to detect a 1ms pulse with a 1ms timer...
> nyquist says you need to sample at at least twice the frequency
> of what you want to resolve.
>
> So you want to use a faster timer or perhaps a Capture input.
> Look at the MSP manual for some (too much) info on Capture.
> For drivers, I don't know what is available in T2, but T1 has:
>    tos\platform\msp430\MSP430TimerC.nc
> and Boomerang:
>     tos\platform\msp430\timer\Counter32khzC.nc
> which may exist in some form in T2 as well.
>
> As to how many interrupts you can process, it pretty much depends on
> how much each int does. Off the top of my head I think the telosb runs
> at 4Mhz with one or two clocks per instruction, so say two...that makes
> about 2000 instructions in 1ms.
>
> MS
>
>
> André Miguel de Almeida Marrão Rodrigues wrote:
>> Hi
>>
>> I just sent it again because is seems the first one did not appear in the 
>> list.
>>
>> André
>>
>> ----- Original Message ----- From: "André Miguel de Almeida Marrão 
>> Rodrigues" <andremiguelrodrigues at gmail.com>
>> To: <tinyos-help at Millennium.Berkeley.EDU>
>> Sent: Wednesday, November 21, 2007 10:15 PM
>> Subject: Pulse detection in T2 TMote port
>>
>>
>>> Hi
>>>
>>> I need do detect a digital 1ms width pulse in tmote port.
>>>
>>> I have modified the TEP 109 - Binary Pin-Connected Sensor in order to 
>>> detect the rising
>>> edge of the sinal (a square sinal with 1ms width) and that worked 
>>> perfect until the day
>>> that I get the node with my device near a WIFI router. Somehow noise 
>>> introduced in the
>>> circuit and there are a few false pulses.
>>>
>>> So now I want to detected the raising edge and the failing edge (using 
>>> the TEP 109 code) and
>>> measure the time between them, which should be arround 1ms. First things 
>>> become complicated
>>> because I'm not sure how to get the uS timer on TMote (so I use the ms 
>>> timer...) and perhaps most importante I'm not sure
>>> if I can process 2 interrupts (with the associated code on the driver 
>>> and on the program) in a 1ms timeframe.
>>>
>>> The code for the driver is the one from the TEP109 (user button); my 
>>> code is:
>>>
>>> event void Notify.notify(bool val) {
>>>
>>> uint32_t begin;
>>>
>>> uint32_t now;
>>>
>>>
>>> if (val == FALSE) {
>>>
>>>  call Timer1ms.startOneShot(2); //just to count the time from the 
>>> raising edge
>>>
>>> }
>>>
>>> else { //so it's a falling edge
>>>
>>> begin = call Timer1ms.gett0();
>>>
>>> now = call Timer1ms.getNow();
>>>
>>> if ((now - begin)< 2000 ){
>>>
>>> .......> a true pulse was detected
>>> Any advice or ideas are much appreciated.
>>>
>>> Regards,
>>>
>>> André Rodrigues
>>>
>>>
>>
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