Federico Tula Rovaletti wrote: > In a program I'm writing in c, when I use the read() function for > reading a byte in the serial port with a configuration: 115200 bps, > 8N2 > > takes from 2ms to 6ms (aleatory, even if read up to 10 bytes takes the > same time), which is too long. > (ioctl(fd, FIONREAD, &bytes) last the same) > > This is the time is suppose to last: > 8 bits: data > 2 bits: stop > 1 bit: start > time = ((8+2+1)bits/115200bps) = 0.095ms, > > then when I read the byte with the function inb_p() takes ~ 0.1ms > which is perfect, what I'm needing for my project. > > The problem I'm having is that I use signals (with fcntl(fd, F_SETFL, > O_ASYNC) ) but this signals last the same time in occur that the > read() (unacceptable) so I guess that this is a problem of the driver > that is to slow. > > So the question is, is there any way to improve the performance of the > driver, or how can I have a faster response with read()? (doing inb_p > is very nasty). Do I'm doing something wrong? Are you using real-time scheduling? Getting such low latency in user space is tricky, but not impossible. You might want to look at JACK (www.jackaudio.org) for clues; they have similar issues -- Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
