Hi,

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?

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!


-- 
Russell Senior, President
russ...@personaltelco.net
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