Hi!
We have three different uart applications (two for production use, and the uart shell backend) and three different hardware output paths, but nRF52840 features just two uart controllers. So we would like to be able to pick any two out of the three applications, and run them on the two controllers using dynamic pin control. We would like to be able to do so dynamically during boot.
So far I can re-route our uarts using the pinctrl_update_states and pinctrl_apply_states.
A problem comes with the uart shell, as we need to dynamically either start it or not, where by not starting I mean to not make it even claim the uart controller.
The minimum config that allows me to compile seems to be:
```
CONFIG_SHELL=y
CONFIG_SHELL_AUTOSTART=n
CONFIG_SHELL_BACKEND_SERIAL=y
CONFIG_UART_CONSOLE=n
```
Now when I set `CONFIG_SHELL_BACKEND_SERIAL=y` and reassign the pins using the pinctrl_* functions then:
- I can start the shell on demand with `shell_start(shell_backend_uart_get_ptr());`
- but when I hook a logic analyzer, I don't see any traffic on the line where I had redirected the production app traffic to. This line and controller is also specified as the dts "chosen" zephyr,shell-uart.
When I set `CONFIG_SHELL_BACKEND_SERIAL=n` and remove all code that relies on it:
- then redirecting the traffic to the other set of lines works fine - I see there the traffic using a logic analyzer
- but I loose the ability to start the shell on uart, since `shell_backend_uart_get_ptr()` is not compiled in without CONFIG_SHELL_BACKEND_SERIAL
I assume that it is because while the shell didn't autostart, the shell backend was automatically initialized at startup and claimed the pins.
How do we compile zephyr in such way that uart shell support is compiled in, but doesn't claim any controller unless told to?
Thanks!
Karel
