[zeromq-dev] zmq_poll on a gpio file descriptor on a beaglebone

[Eric Hill]

Do you have access to the python threading library on that board? If so, I
would poll the gpio pin in one thread, the zmq socket in a second thread,
and have both threads signal a mutex that your main thread is waiting on.
On Feb 28, 2013 5:37 PM, "Craig Swank" <craigswank at gmail.com> wrote:

> I'm trying use zmq_poll to poll both a zmq_socket and a file descriptor
> for a gpio input pin on a beaglebone using pyzmq.  Does anyone know if this
> is possible?  I wrote a python script that tries to poll on the gpio pin
> only (in order to keep the example as simple as possible).  After opening
> an issue at pyzmq and some back and forth with the person who responded to
> my issue, it seems that what I'm asking for is not supported.
>
> My question, is what I'm asking for supported, and if not should I issue a
> feature request with zmq?
>
> Here is the example script.  I have two functions - wait and zmq_wait.
> wait blocks until I press a button connected to the gpio pin on the
> beaglebone.  zmq_wait never blocks::
>
>     import os, select, time
>     import zmq
>
>     class MyObj(object):
>         """
>         Pyzmq docs claim that any object
>         that provides a 'fileno' function
>         can be passed to the register function
>         of the zmq.Poller
>         """
>         def __init__(self, fd):
>             self.fd = fd
>
>         def fileno(self):
>             return self.fd
>
>
>     def wait(fd):
>         os.read(fd, 2)
>         poller = select.poll()
>         poller.register(fd, select.POLLPRI)
>         events = poller.poll(-1)
>         os.lseek(fd, 0, 0)
>         val = os.read(fd, 2)
>         print 'poller returned', val
>
>
>     def zmq_wait(fd):
>         os.read(fd, 2)
>         poller = zmq.Poller()
>         poller.register(fd, zmq.POLLIN)
>         events = poller.poll(-1)
>         os.lseek(fd, 0, 0)
>         val = os.read(fd, 2)
>         print 'zmq poller returned', val
>
>     path = '/sys/class/gpio/gpio89/value'
>     #the gpio pin has already been configured as input, and to trigger an
> event
>     #on a rising edge by doing "echo 'rising' >
> /sys/class/gpio/gpio89/edge"
>     fd = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
>
>     #this function blocks until I push the button
>     zmq_wait(fd) #returns immediately
>
>     wait(fd) #blocks until I push the button connected to the gpio pin
>
>
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