[PD-dev] while loop segfault

[Martin Peach]

Oh sorry, I thought you were using an arduino.

Martin

On Tue, Oct 14, 2014 at 1:16 PM, Colet Patrice <colet.patrice at free.fr>
wrote:

>  Le 14/10/2014 15:06, Martin Peach a écrit :
>
>  Not sure why it segfaults, just want to say that that method is really
> bad. Because of Pd's control rate as well as the serial interface latency,
> your timing will be really sketchy. The way to do what you want is to
> implement the ranging entirely on the arduino and send the values back to
> Pd via [comport]. So a Pd [pulseIn] object shoud simply send a request to
> the arduino to start a pulse and return the time. It could be implemented
> as an abstraction containing [comport].
>
>
> I'm not using serial to read gpio state but fopen() (may be fopen() is not
> fast enough), like in a raspberry (but it's not on raspberry), I will try
> to do this with python and use pdsend for retrieving value into puredata.
> thank you for the advice.
> pc
>
>
>  Martin
>
> On Mon, Oct 13, 2014 at 9:29 PM, Colet Patrice <colet.patrice at free.fr>
> wrote:
>
>> Hello, I'm trying to implement the pulseIn() function we can find in
>> arduino libraries into an external.
>>
>> I couldn't make it work because some part doesn't seem to behave like I
>> expect so I'm wondering if it's caused by puredata process,
>> so maybe someone in the list could enlight me about that.
>>
>> The purpose of the external is about using an ultrasound sensor connected
>> on gpio that require a microsecond timer for getting distance like this:
>>
>>
>> //here is a custom timer using a struct provided by pcduino headers:
>> #include core.h
>> unsigned long pat_micros() {
>>     struct timeval tv;
>>     gettimeofday(&tv,NULL);
>>     return tv.tv_sec*(uint64_t)1000000+tv.tv_usec;
>> }
>>
>> //here is the custom pulseIn() function:
>> unsigned long pat_pulseIn(t_pdpcduino *x, int pin)
>> {
>>     unsigned long timeout = 100000;
>>     unsigned long start = pat_micros();
>>
>>     while( pdpcduino_gpio_read2 (x, pin) == 1 )
>>         if( pat_micros() - start > timeout )
>>             return 0;
>>
>> // this is where I'm getting a segmentation fault:
>>
>>     while ( pdpcduino_gpio_read2 (x, pin) == 0 )
>>         if( pat_micros() - start > timeout )
>>         return 0;
>>
>> //...
>>     unsigned long value = pat_micros();
>>
>>     while( pdpcduino_gpio_read2 (x, pin) == 1 )
>>         if( pat_micros() - start > timeout )
>>             return 0;
>>
>>     return pat_micros() - value;
>>
>> }
>>
>> //...
>>
>>
>> If I reduce the timeout number, segfault comes randomly after this
>> function has been triggered, so I'm wondering if this method is really
>> appropriate,
>> is there an exemple of external (containing such while loops) I could get
>> inspired from to write this pulseIn() function?
>>
>>
>>
>>
>>
>>
>> _______________________________________________
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>> Pd-dev at lists.iem.at
>> http://lists.puredata.info/listinfo/pd-dev
>>
>
>
>
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