Gilles Chanteperdrix wrote: > Alexis Berlemont wrote: > > Hi, > > > > Daniele Nicolodi wrote: > >> Hello. In my application I need to read data from an ADC card in blocks > >> of a given number of samples. For efficiency I'm using an mmapped buffer > >> to exchange data with the ADC driver. I'm setting up the acquisition, > >> and then calling a loop like this: > >> > >> unsigned int required = <compute required number of bytes>; > >> unsigned int read = 0; > >> while (1) { > >> while (read < required) { > >> read = a4l_pool(...); > >> } > >> process(buffer, ...); > >> } > >> > >> However if I run this loop in a real time thread the tight while loop is > >> an obvious cpu hog: the watchdog kicks in and kills the thread. > >> > >> There is not an analogy API that can be used to require a certain amount > >> of data to the ADC driver. How can I code this loop to let other > >> processes to run? > > > > As a matter of fact, there is something in the API which could have > > helped you in an unmapped configuration. If you set the flag > > A4L_CMD_BULK in the field "flags" of the command structure, a call to > > a4l_async_read() only returns when the data size specified as argument > > is available. > > > > Unfortunately, I have not done the same thing with a4l_poll, I might > > have added the requested size as an additional argument to a4l_poll. > > > > Any idea on how to extend the API without breaking it ? > > Maybe it would be possible to use the standard "select" call, with a > threshold configurable with an ioctl ?
Thanks. I added your idea in my TODO list. > > > -- > Gilles. -- Alexis. _______________________________________________ Xenomai-help mailing list Xenomai-help@gna.org https://mail.gna.org/listinfo/xenomai-help