Move selection of UART interface and baudrate to picoprobe_config.h

[lurch]

Fixes #1

[kilograham]

This refers to the base code too, but what is the benefit in general of not using

PICO_DEFAULT_UART_BAUD_RATE (_TX_PIN, RX_PIN etc) as the default values for PICOPROBE values unless they are defined by the user

i;.e

#ifndef PICOPROBE_UART_TX
#define PICOPROBE_UART_TX PICO_DEFAULT_UART_TX_PIN
#endif

which i'd prefer

[lurch]

I guess the answer to that depends on why @liamfraser opted to use UART pins 4 and 5 in the first place, instead of just sticking to the default 0 and 1 ? 🤷‍♂️

[lurch]

Also, if picoprobe_config.h switches to using

#ifndef PICOPROBE_UART_TX
#define PICOPROBE_UART_TX PICO_DEFAULT_UART_TX_PIN
#endif

where does the definition of a non-default PICOPROBE_UART_TX move to? CMakeLists.txt? Only allow it to be specified on the cmake command line? (I'm not being facetious, I'm genuinely curious)

[kilograham]

yes it would from CMakeLists.txt (which could (should) choose to pick it up from the command line or environment)

[liamfraser]

The reason it is done like this is so you can use the default uart as a debug uart and uart1 as the uart that binds to usb

[lurch]

I've never written any CMake before. But poking around in some of the other cmake files, would I want to do something like this?

if (DEFINED ENV{PICOPROBE_UART_TX} AND (NOT PICOPROBE_UART_TX))
    set(PICOPROBE_UART_TX $ENV{PICOPROBE_UART_TX})
    message("Using PICOPROBE_UART_TX from environment (${PICOPROBE_UART_TX})")
else ()
    set(PICOPROBE_UART_TX 4)
endif ()

🤷