Sys-tick resolution is 1ms and a value of 2 will give a delay between 1ms
and 2ms (whereas a value of 1 gives a delay between 0ms and 1ms, which is
too short).
The HAL_UART_Transmit function has changed in the latest HAL version such
that the Timeout is a timeout for the entire function, rather than a
timeout between characters as it was before. The HAL function also does
not allow one to reliably tell how many characters were sent before the
timeout (if a timeout occurred).
This patch provides a custom function to do UART transmission, completely
replacing the HAL version, to fix the above-mentioned issues.
UART REPL support was lost in os.dupterm() refactorings, etc. As
os.dupterm() is there, implement UART REPL support at the high level -
if MICROPY_STDIO_UART is set, make default boot.py contain os.dupterm()
call for a UART. This means that changing MICROPY_STDIO_UART value will
also require erasing flash on a module to force boot.py re-creation.
There is a minor functional change with this patch, that the GPIO are now
configured in fast mode, whereas they were in high speed mode before. But
the SDIO should still work because SD CK frequency is at most 25MHz.
They are the same as the existing raw constants (namely 0, 1, 2) but we
want to explicitly show that one can use the HAL's constants if necessary
(eg the mpconfigboard.h files do use the HAL's constants to define the
pull state of certain configurable pins).
Paul Sokolovsky
Damien George
Rami Ali
sergiuszm