For STM32 targets using a 32-bit timer for the microsecond ticker, the
driver did not properly handle timestamps that are in the past. It
would just blindly set the compare register to the requested timestamp,
resulting in the interrupt being serviced up to 4295 seconds late
(i.e. after the 32-bit timer counts all the way around to hit the
timestamp again).
This problem can easily be reproduced by creating a Timeout object
then calling the timeout's attach_us() member function to attach a
callback with a timeout of 0 us. The callback will not get called for
over 2147 seconds, and possibly up to 4295 seconds late if no other
microsecond ticker events are getting scheduled in the meantime.
Now, after the compare register has been set, the timestamp is checked
against the current time to see if the timestamp is in the past, and
if so, the compare event is manually set.
NOTE: By checking if the timestamp is in the past after configuring the
capture register, we ensure proper handling in the case where the timer
updates past the timestamp while setting the capture register.
The STM32F3 cmsis_nvic code is currently checking for a specific flash
address when determining if the vector table is in flash or RAM. By
changing the test to instead see if the vector table base is NOT set to
the RAM address, it simplifies the code, and removes the dependency on
the flash vectors being located at a specific address. This becomes
important when adding a custom boot loader, which requires that the
flash vector table location in the mbed project be at a different
address.
bcostm
Jimmy Brisson
Sam Grove
Bradley Scott
Bartek Szatkowski
adustm