This patch makes it so that UART(0) can by dynamically attached to and
detached from the REPL by using the uos.dupterm function. Since WebREPL
uses dupterm slot 0 the UART uses dupterm slot 1 (a slot which is newly
introduced by this patch). UART(0) must now be attached manually in
boot.py (or otherwise) and inisetup.py is changed to provide code to do
this. For example, to attach use:
import uos, machine
uart = machine.UART(0, 115200)
uos.dupterm(uart, 1)
and to detach use:
uos.dupterm(None, 1)
When attached, all incoming chars on UART(0) go straight to stdin so
uart.read() will always return None. Use sys.stdin.read() if it's needed
to read characters from the UART(0) while it's also used for the REPL (or
detach, read, then reattach). When detached the UART(0) can be used for
other purposes.
If there are no objects in any of the dupterm slots when the REPL is
started (on hard or soft reset) then UART(0) is automatically attached.
Without this, the only way to recover a board without a REPL would be to
completely erase and reflash (which would install the default boot.py which
attaches the REPL).
This patch simplifies the str creation API to favour the common case of
creating a str object that is not forced to be interned. To force
interning of a new str the new mp_obj_new_str_via_qstr function is added,
and should only be used if warranted.
Apart from simplifying the mp_obj_new_str function (and making it have the
same signature as mp_obj_new_bytes), this patch also reduces code size by a
bit (-16 bytes for bare-arm and roughly -40 bytes on the bare-metal archs).
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
