This is a hack to free up TIM3 so that it can be used by the user.
Instead we use the PVD irq to call the USB VCP polling function, and
trigger it from SysTick (so SysTick itself does not do any processing).
The feature is enabled for pyboard lite only, since it lacks timers.
Consider the following scenario: SD card is being read by pyboard; USB
irq comes in for MSC read request; SD card needs to be read from within
USB irq while SD read is already ongoing. Such contention needs to be
avoided.
This patch provides a simple solution, to raise the irq priority above
that of the USB irq during SD DMA transfers. Pyboard and PC can now
read from the SD card at the same time (well, reads are interleaved).
In non-blocking mode (timeout=0), uart.write() can now transmit all of its
data without raising an exception. uart.read() also works correctly in
this mode.
As part of this patch, timout_char now has a minimum value which is long
enough to transfer 1 character.
Addresses issue #1533.
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).
Turning on each DMA block increases the current consumption
by about 8 mA. This code adds an idle timer for each DMA
block and turns off the clocks when no streams are in use
for 128 msec. Having a small timeout allows for improved
performance when back-to-back transfers are being performed.
The 128 msec is basically a guess.
- added some comments to explain the priority/sub-priority.
- adds an entry for SDIO (to be used in a later patch)
- increases DMA priority above USB so that DMA can be used
for sdcard I/O when using USB Mass Storage.
If RTC is already running at boot then it's left alone. Otherwise, RTC is
started at boot but startup function returns straight away. RTC startup
is then finished the first time it is used. Fallback to LSI if LSE fails
to start in a certain time.
Also included:
MICROPY_HW_CLK_LAST_FREQ
hold pyb.freq() parameters in RTC backup reg
MICROPY_HW_RTC_USE_US
option to present datetime sub-seconds in microseconds
MICROPY_HW_RTC_USE_CALOUT
option to enable RTC calibration output
CLK_LAST_FREQ and RTC_USE_CALOUT are enabled for PYBv1.0.
In new hardware API, these classes implement master modes of interfaces,
and "mode" parameter is not accepted. Trying to implement new HW API
in terms of older pyb module leaves variuos corner cases:
In new HW API, I2C(1) means "I2C #1 in master mode" (? depends on
interpretation), while in old API, it means "I2C #1, with no settings
changes".
For I2C class, it's easy to make mode optional, because that's last
positional param, but for SPI, there's "baudrate" after it (which
is inconsistent with I2C, which requires "baudrate" to be kwonly-arg).
This makes select.poll() interface fully compatible with CpYthon. Also, make
their numeric values of these options compatible with Linux (and by extension,
with iBCS2 standard, which jopefully means compatibility with other Unices too).
py/mphal.h contains declarations for generic mp_hal_XXX functions, such
as stdio and delay/ticks, which ports should provide definitions for. A
port will also provide mphalport.h with further HAL declarations.
This prevents the loss of RTC time when exiting from standby mode, since
the RTC is paused while it is being re-inited and this loses about 120ms.
Thanks to @chuckbook for the patch.
