[ +CC: linux-usb] Hi Doug, On Mon, Nov 17, 2014 at 12:23:05AM -0500, Douglas Gilbert wrote: > Hi, > I just ran into the "lots ** of spurious zeros on read" problem > with a XBee reader adapter (for USB) from Sparkfun. It is really > annoying. Looked around and your name popped up on a linux-usb > thread whose name is in the subject line. > > I have two different adapters: > - FT232RL based that has the "spurious zeros" problem > - FT231X based that works fine > > Probably related to the spurious zeros appearing in my test code > is this in syslog: > ftdi_sio ttyUSB0: usb_serial_generic_read_bulk_callback - > nonzero urb status: -71 Do see this during normal operation? Or when disconnecting an open port? In the former case it could indicate a hardware problem. > I'm using lk 3.17.3 . Has there been any resolution to this problem? The issue in the thread you refer to is a hardware one that is causing overruns, which in turns gets reported as NULL-bytes. [ The driver bug that is also discussed is only about whether it is possible to disable this error reporting. ] > Doug Gilbert > > ** my read()s are for 200 bytes and when this problem occurs, it > reads 200 bytes of zeros. And there is no LED illumination on the > XBee adapter that would usually indicate inbound data. This at > 9600 baud so 200 chars would take at least 2 seconds. Have you checked the interrupt counters (TIOCMGICOUNT ioctl) to see if there have been overruns when this occurs? You should also see it, albeit in a more raw form, in the status bytes from the device if you enable debugging in usbserial. Thanks, Johan -- 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
