With these you can now do things like:
stm.mem32[0x20000000] = 0x80000000
and read 32-bit values. You can also read all the way to the end
of memory using either stm.mem32[0xfffffffc] or stm.mem32[-4].
IRQs shouldn't use mem32 at all since they'd fail if the top 2 bits
weren't equal, so IRQs should be using 16-bit I/O.
The STMCube examples define both USE_USB_HS and USE_USB_HS_IN_FS when they
use the HS in FS mode.
The STM32F401 doesn't have a USB_HS at all, so the USB_OTG_HS instance
doesn't even exist.
The UARTs have no FIFOs, so if interrupts are disabled
for more than a character time (10 usec at 1 Mbit/sec)
then characters get dropped.
The overhead for handling a UART ISR is about 0.5 usec,
so even at baud rates of 1 Mbit/sec this only corresponds
to about 5% of the CPU. Lower baud rates will have less
of an impact.
uwTick can only change in the SysTick IRQ so this IRQ function does not
need to take special care with this variable. It's important to make
this IRQ function as efficient as possible.
Using SysTick to do the counting and dispatch of the flash storage idle
handler is more efficient than requiring a dedicated hardware timer.
No new counter is needed, just the existing uwTick variable. The
processing is not actually done in the SysTick IRQ, it is deferred to
the flash IRQ (which runs at lower priority).
Paul Sokolovsky
Damien George
Dave Hylands
Tobias Badertscher