Hi Sudhir,
If you are not well versed in Linux and C then the speed of your own
code will be no faster than using my library with debugging disabled I
imagine.
Without looking seriously at your code there are two things I want to say.
1) You should be using POLLPRI - look at my library for an example
2) Poll does not introduce 150ms latency
If you run the tests included with my libsoc library you will see that
it can service 10,000 interrupts in a non-blocking context in roughly 3
seconds on a beaglebone white. That's per interrupt and simple ISR style
routine. I would be suprised if you could get it much faster than that
using standard read/write file techniques.
If you really want to roll your own, and are still struggling then just
base it off my library. That way you have a fully working example to
compare your code with.
Cheers,
Jack.
On 10/21/13 19:08, sudhir v wrote:
Hi Jack,
Thanks for the help!. I looked at your library and it appears that you
are using poll(2) as well which is similar to the example I am trying
to use in the original post.
There are two things I want to mention
1. Latency : I came across somewhere that poll() by itself introduces
150ms latency which is not good for the system I am building. (But I
want it to work first) And you have mentioned that the library is
optimized for reliability rather than speed.
2. Complexity : Interrupt capture is just a small part of the system I
am building and I want the code to be as simple and little as
possible. This Code
<https://developer.ridgerun.com/wiki/index.php/Gpio-int-test.c> appears to
be simple enough and does just the functionality.
Since you have built the library, Can you please just point out where
in the code I might be going wrong? The problem might be trivial but I
am missing something. I am using POLLIN and it continuously outputs
GPIO 117 interrupt occurred even though I have not connected any
signals to GPIO 117. More details/analysis done in the original post.
Thank you!
sudhir.
On Friday, 18 October 2013 13:25:09 UTC-4, Jack Mitchell wrote:
Sudhir,
If you don't object to using a library there is libsoc[1] which is
made
for this exact purpose.
https://github.com/jackmitch/libsoc
<https://github.com/jackmitch/libsoc>
Cheers,
Jack.
On 18/10/2013 17:31, sudhir v wrote:
>
> Hi,
>
> I want to monitor a pin on BBB for interrupt. I chose pin 117
(pin 25 on
> P9 -> GPIO3_21 = 32*3+21 = 117. I hope that's correct?)
> I came across this question on stackoverflow
>
<http://stackoverflow.com/questions/3021146/poll2-doesnt-empty-the-event-queue
<http://stackoverflow.com/questions/3021146/poll2-doesnt-empty-the-event-queue>>.
> And This is my question on stackoverflow
>
<http://stackoverflow.com/questions/19434157/poll-to-monitor-a-pin-on-beaglebone-black-continuous-output-even-though-pin-n
<http://stackoverflow.com/questions/19434157/poll-to-monitor-a-pin-on-beaglebone-black-continuous-output-even-though-pin-n>>
> I am following this program from ridgerun
> <https://developer.ridgerun.com/wiki/index.php/Gpio-int-test.c
<https://developer.ridgerun.com/wiki/index.php/Gpio-int-test.c>>
and made
> minor changes since I want to monitor just one pin and not any
other
> files. Changes are highlighted in the code below which I am
trying to
> run. (I have pasted just the main. Rest is the same as the code
from the
> site)
> The problem is, when I run the program, it continuously outputs
"poll()
> GPIO 117 interrupt occurred" even though I haven't connected
anything to
> that particular pin and I have to do ctrl+C to stop the execution.
> POLLPRI does not work and the program prints just ... after every
> timeout and I think POLLIN is proper since it is not a priority
data.
>
> Where am I going wrong?
>
> I read about potential problems and the program seems to take
care of
> the below.
> 1. The poll() doesn't fail.
> 2. read() is called after every poll() so data should be
consumed. ( I
> just want the program to notify whenever there is a rising edge
saying
> there is an event occured. I do not want to read data from pin. but
> included this to avoid potential pitfalls)
> 3. struct pollfd is being reset inside while loop (
> memset((void*)fdset,0,sizeof(fdset)); )
>
> |
>
> int main(int argc, char **argv)
> {
> *struct pollfd fdset[1];*
> *int nfds= 1;*
> int gpio_fd, timeout, rc;
> char *buf[MAX_BUF];
> unsigned int gpio;
> int len;
> if (argc< 2) {
> printf("Usage: gpio-int <gpio-pin>\n\n");
> printf("Waits for a change in the GPIO pin
voltage level or input on stdin\n");
> exit(-1);
> }
> gpio= atoi(argv[1]);
> gpio_export(gpio);
> gpio_set_dir(gpio, 0);
> gpio_set_edge(gpio, "rising");
> gpio_fd= gpio_fd_open(gpio);
> timeout= POLL_TIMEOUT;
> while (1) {
> memset((void*)fdset, 0, sizeof(fdset));
> *fdset[0].fd= gpio_fd;
> fdset[0].events= POLLIN;*
> rc= poll(fdset, nfds, timeout);
> if (rc< 0) {
> printf("\npoll() failed!\n");
> return -1;
> }
> if (rc== 0) {
> printf(".");
> }
> *if (fdset[0].revents& POLLIN) {
> len= read(fdset[0].fd, buf, MAX_BUF);*
> printf("\npoll() GPIO %d interrupt
occurred\n", gpio);
> }
> fflush(stdout);
> }
> gpio_fd_close(gpio_fd);
> return 0;
> }
>
> |
>
> Thanks,
> sudhir
>
> --
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