Thanks for taking the time to respond.
Answers to your questions:
I'm not using any hubs.
The adapter I'm using is a simple FTDI USB <-> RS-232(TTL) adapter that works for everything else. Windows 10 has no problem with it.
My 'loopback' is just a wire between TxD and RxD. The device has LEDs on both lines, and they flash nicely when using Bray's TERMINALin Windows - regardless of what baud rate I choose. I get chars in the receive window when I press a key. Those chars stop when I remove the loopback wire.
There are no cable issues.
dmesg reports the following:
[ 2632.764056] usb 1-1.3: Product: FT232R USB UART
[ 2632.764068] usb 1-1.3: Manufacturer: FTDI
[ 2632.764081] usb 1-1.3: SerialNumber: A50285BI
[ 2632.772529] ftdi_sio 1-1.3:1.0: FTDI USB Serial Device converter detected
[ 2632.772759] usb 1-1.3: Detected FT232RL
[ 2632.773634] usb 1-1.3: FTDI USB Serial Device converter now attached to ttyUSB0
stty reports the following:
:~ $ stty -F /dev/ttyUSB0
speed 0 baud; line = 0;
intr = <undef>; quit = <undef>; erase = <undef>; kill = <undef>; eof = <undef>; start = <undef>;
stop = <undef>; susp = <undef>; rprnt = <undef>; werase = <undef>; lnext = <undef>; flush = <undef>;
min = 0; time = 0;
-brkint -icrnl -imaxbel
-isig -icanon -iexten -echo -echoe -echok -echoctl -echoke
I have tried every conceivable port. I'm already using ttyAMA0. I tried serial0, serial1,tty0,ttyS0. minicom hangs on all of them.
I logged out and logged in again. No difference.
Could it be that I need a driver? One is not supposed to be needed, but ....
I think I would be better off moving to an Orange pi zero. It has 3 actual serial ports.