Can't get loopback serial communication to work

[Nathan_Strong]

sure.

Some additional details:

$ uname -a
Linux lafrite 6.0.13-meson64 #22.11.2 SMP PREEMPT Sun Dec 18 16:52:19 CET 2022 aarch64 aarch64 aarch64 GNU/Linux

I’m pretty confident the devices are correct. Here’s the dmesg output for the FTDI adapter from when the USB end of the cable is attached:

[  330.376285] ftdi_sio 1-2:1.0: FTDI USB Serial Device converter detected
[  330.376580] usb 1-2: Detected FT232RL
[  330.378398] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB0

For the other end, /dev/ttyAML6 didn’t exist until I adapted these steps:

How to enable UART A and 921600 Baud Rate for AML-S805X-AC and AML-S905X-CC

UART A is on pin 8 and pin 10 with optional flow control on pin 16 and pin 18. sudo ldto enable uarta sudo stty -F /dev/ttyAML6 921600 To support the 921600 and other specific baud rate, a different dtoverlay uarta-clk81 must be used in place of uarta. sudo ldto enable uarta-clk81 sudo stty -F /dev/ttyAML6 921600 There are also other hardware UARTs available and even software UART that can be created on most pins. UART AO B on pin 3 and pin 5. UART C on pin 19 and pin 21 with optional flow…

I say “adapted” because I wasn’t able to use the libretech wiring tool to install the DTO. but Armbian provides (or at least seems to provide) the same functionality via the overlays= directive in armbianEnv.txt.

Also, permissions look good. Both devices are r/w for the dialout group and my armbian user belongs to that group.

I’ll try shorting TX to RX and see what happens.