Use uos.dupterm for REPL configuration of the main USB_VCP(0) stream on
dupterm slot 1, if USB is enabled. This means dupterm can also be used to
disable the boot REPL port if desired, via uos.dupterm(None, 1).
For efficiency this adds a simple hook to the global uos.dupterm code to
work with streams that are known to be native streams.
These macros are unused, and they can conflict with other entities by the
same name. If needed they can be provided as static inline functions, or
just functions.
Fixes issue #4559.
Adds support for hardware i2c to the zephyr port. Similar to other ports
such as stm32 and nrf, we only implement the i2c protocol functions
(readfrom and writeto) and defer memory operations (readfrom_mem,
readfrom_mem_into, and writeto_mem) to the software i2c implementation.
This may need to change in the future because zephyr is considering
deprecating its i2c_transfer function in favor of i2c_write_read; in this
case we would probably want to implement the memory operations directly
using i2c_write_read.
Tested with the accelerometer on frdm_k64f and bbc_microbit boards.
For gpio_hold_en() to work properly (not draw additional current) pull
up/down must be disabled when hold is enabled. This patch makes sure this
is the case by reworking the pull constants to be a bit mask.
Adding section about on how to disable use of the linker flag
-flto, by setting the LTO=0 argument to Make. Also, added a
note on recommended toolchains to use that works well with
LTO enabled.