[PD-dev] while loop segfault
Colet Patrice
colet.patrice at free.fr
Tue Oct 14 19:16:40 CEST 2014
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
> <mailto: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?
>
>
>
>
>
>
> _______________________________________________
> Pd-dev mailing list
> Pd-dev at lists.iem.at <mailto:Pd-dev at lists.iem.at>
> http://lists.puredata.info/listinfo/pd-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puredata.info/pipermail/pd-dev/attachments/20141014/abdd43fb/attachment.html>
More information about the Pd-dev
mailing list