On Wed, Dec 07, 2016 at 04:42:21AM -0800, Russell Senior wrote: > I just bought a bag of usb-serial converters off of ebay, from china for > super low price (~$2/each). I just plugged a couple of them in, > connected together through a null-modem adapter. When I plug them, on > both stock ubuntu 16.04's kernel and 4.8.9 built from git, I get a > reasonable looking dmesg: > > [822616.501963] usb 2-2.3: new full-speed USB device number 16 using xhci_hcd > [822616.602985] usb 2-2.3: New USB device found, idVendor=1a86, idProduct=7523 > [822616.602988] usb 2-2.3: New USB device strings: Mfr=0, Product=2, SerialNumber=0 > [822616.602989] usb 2-2.3: Product: USB2.0-Ser! > [822617.633618] usbcore: registered new interface driver usbserial > [822617.633638] usbcore: registered new interface driver usbserial_generic > [822617.633653] usbserial: USB Serial support registered for generic > [822617.638736] usbcore: registered new interface driver ch341 > [822617.638755] usbserial: USB Serial support registered for ch341-uart > [822617.638770] ch341 2-2.3:1.0: ch341-uart converter detected > [822617.640272] usb 2-2.3: ch341-uart converter now attached to ttyUSB0 > [822625.294363] usb 2-2.2: new full-speed USB device number 17 using xhci_hcd > [822625.395324] usb 2-2.2: New USB device found, idVendor=1a86, idProduct=7523 > [822625.395327] usb 2-2.2: New USB device strings: Mfr=0, Product=2, SerialNumber=0 > [822625.395328] usb 2-2.2: Product: USB2.0-Ser! > [822625.396487] ch341 2-2.2:1.0: ch341-uart converter detected > [822625.397575] usb 2-2.2: ch341-uart converter now attached to ttyUSB1 > > I attach the tty's with GNU screen (but I have also tried microcom and > minicom with the same results). This was my first experience with or > even awareness of ch341. I have much more experience with pl2303 and > somewhat less with ftdi. With these ch341, when I type in an 'a' on one > terminal, I get 0x01 out the other terminal. If I type in a 'b', I get > an 0x02, etc, on up to 'z' yielding 0x1a. > > I found your name/contact in the git commits. > > Any idea what is going on? Sounds like it could be related to an incorrect line setting (e.g. the devices are using 5-bit words). Some changes just went in that add support for changing this. Could you try building a kernel based on the usb-next branch of: git://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git and see if that works better? > My leading theory at the moment is that the manufacturer didn't populate > all the parts, and the vendor got an great deal on them, which they > passed on to me! Note that some of these converters use TTL-level signalling which could appear as corrupt transfers if you try to connect it to an RS232 port (but not when connecting to another device also using TTL). 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
