Hi Greg, On Tue, Feb 27, 2018 at 4:16 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > 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 I'm not sure I understand what you mean by the physical loopback device? Do you mean the Prolific PL2303 device, or the modem, or something else? -- -brent -- 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
