On Mon, Feb 26, 2018 at 10:05:35PM -0500, Brent Sink wrote: > Hello, > > I'm trying to debug a problem I'm having with a usb-serial device > (modem) when it's plugged into a USB port on a custom i.MX6 board. > > If I connect a USB to Serial converter (I'm using Prolific PL2303), > and I short the RX and TX lines together so I read back what I write, > I've noticed that I can send data correctly, but when I receive data > it is missing the LSB. I've verified this by using a logic analyzer > to make sure that when I type "A", the logic analyzer also reads "A". > But when looking at the echo from minicom, it shows "@" instead. "B" > = "B", "C" = "B", "D" = "D", "E" = "D", and so on. This same problem > happens to the 3G and 4G modems, as they create ttyACMx ports and > ModemManager is unable to talk to them because of this same issue. > This happens on every board we had made, and I've tried using both > Buildroot and Debian in case it was a rootfs issue... it's not. I > also tried using a 3.14 kernel and 4.1.15 kernel - same problem exists > in both versions. This sounds like you have a problem with your physical loopback device. I suggest getting a different one and trying that out. good luck! greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
