This patch makes the DAC driver simpler and removes the need for the ST
HAL. As part of it, new helper functions are added to the DMA driver,
which also use direct register access instead of the ST HAL.
Main changes to the DAC interface are:
- The DAC uPy object is no longer allocated dynamically on the heap,
rather it's statically allocated and the same object is retrieved for
subsequent uses of pyb.DAC(<id>). This allows to access the DAC objects
without resetting the DAC peripheral. It also means that the DAC is only
reset if explicitly passed initialisation parameters, like "bits" or
"buffering".
- The DAC.noise() and DAC.triangle() methods now output a signal which is
full scale (previously it was a fraction of the full output voltage).
- The DAC.write_timed() method is fixed so that it continues in the
background when another peripheral (eg SPI) uses the DMA (previously the
DAC would stop if another peripheral finished with the DMA and shut the
DMA peripheral off completely).
Based on the above, the following backwards incompatibilities are
introduced:
- pyb.DAC(id) will now only reset the DAC the first time it is called,
whereas previously each call to create a DAC object would reset the DAC.
To get the old behaviour pass the bits parameter like: pyb.DAC(id, bits).
- DAC.noise() and DAC.triangle() are now full scale. To get previous
behaviour (to change the amplitude and offset) write to the DAC_CR (MAMP
bits) and DAC_DHR12Rx registers manually.
Instead of checking each callback (currently storage and dma) explicitly
for each SysTick IRQ, use a simple circular function table indexed by the
lower bits of the millisecond tick counter. This allows callbacks to be
easily enabled/disabled at runtime, and scales well to a large number of
callbacks.
For a given IRQn (eg UART) there's no need to carry around both a PRI and
SUBPRI value (eg IRQ_PRI_UART, IRQ_SUBPRI_UART). Instead, the IRQ_PRI_UART
value has been changed in this patch to be the encoded hardware value,
using NVIC_EncodePriority. This way the NVIC_SetPriority function can be
used directly, instead of going through HAL_NVIC_SetPriority which must do
extra processing to encode the PRI+SUBPRI.
For a priority grouping of 4 (4 bits for preempt priority, 0 bits for the
sub-priority), which is used in the stm32 port, the IRQ_PRI_xxx constants
remain unchanged in their value.
This patch also "fixes" the use of raise_irq_pri() which should be passed
the encoded value (but as mentioned above the unencoded value is the same
as the encoded value for priority grouping 4, so there was no bug from this
error).
The problem is the existing code which tries to optimise the
reinitialisation of the DMA breaks the abstraction of the HAL. For the
STM32L4 the HAL's DMA setup code maintains two private vars (ChannelIndex,
DmaBaseAddress) and updates a hardware register (CCR).
In HAL_DMA_Init(), the CCR is updated to set the direction of the DMA.
This is a problem because, when using the SD Card interface, the same DMA
channel is used in both directions, so the direction bit in the CCR must
follow that.
A quick and effective fix for the L4 is to simply call HAL_DMA_DeInit() and
HAL_DMA_Init() every time.
The CMSIS files for the STM32 range provide macros to distinguish between
the different MCU series: STM32F4, STM32F7, STM32H7, STM32L4, etc. Prefer
to use these instead of custom ones.
Newer versions of the HAL use names which are cleaner and more
self-consistent amongst the HAL itself. This patch switches to use those
names in most places so it is easier to update the HAL in the future.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
