[Tinyos-help] Pulse detection in T2 TMote port

[André Miguel de Almeida Marrão Rodrigues]

That was nice. But the signal line is a 3cm large copper trace in a PCB...

Thanks again

André

----- 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 7:21 PM
Subject: Re: [Tinyos-help] Pulse detection in T2 TMote port


> perhaps a little ferrite bead on your signal wire would
> kill some RF interference...
> MS
>
>
> André Miguel de Almeida Marrão Rodrigues wrote:
>> 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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