On Mon, Dec 12, 2011 at 11:51:02AM +0100, Jérôme Stadelmann wrote: > Hello everybody, > > I've actually some problem when trying to read data from a u-blox > LEA-6T USB module. My kernel is the 2.6.34 and I'm using the cdc_acm > driver to read data from the GPS. > > The GPS is sending a packet every second, but when I try a "hexdump > /dev/ttyACM0", <file:///dev/ttyACM0%22%2C> I do only receive some > data every 5, 10 or even 20 seconds instead of every second as if it > has been buffering the data. But I am receiving the correct number > of packets (for example 10 every 10 seconds, 5 every 5, etc.). I'm > also losing some data (a few bytes) when I receive the data. > > I've checked with a few kernels and linux distros, and I haven't > been able to find some coherency. If you look at the "raw" USB data, using usbmon, do you also see the buffering happening on the wire? Or is the kernel doing it? I'd bet that the device is doing this, as the kernel really only passes along the data as it receives it. You should also use a "real" serial program, like minicom, to watch the data, not hexdump, that might help here. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
