This commit adds support for the STM32G4 series of MCUs, and a board
definition for NUCLEO_G474RE. This board has the REPL on LPUART1 which is
connected to the on-board ST-link USB-UART.
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.
With this and previous patches the stm32 port can now be compiled using
object representation D (nan boxing). Note that native code and frozen mpy
files with float constants are currently not supported with this object
representation.
This can be used to select the output buffer behaviour of the DAC. The
default values are chosen to retain backwards compatibility with existing
behaviour.
Thanks to @peterhinch for the initial idea to add this feature.
Rather than pin objects themselves. The actual object is now pin_X_obj and
defines are provided so that pin_X is &pin_X_obj. This makes it so that
code that uses pin objects doesn't need to know if they are literals or
objects (that need pointers taken) or something else. They are just
entities that can be passed to the map_hal_pin_xxx functions. This mirrors
how the core handles constant objects (eg mp_const_none which is
&mp_const_none_obj) and allows for the possibility of different
implementations of the pin layer.
For example, prior to this patch there was the following:
extern const pin_obj_t pin_A0;
#define pyb_pin_X1 pin_A0
...
mp_hal_pin_high(&pin_A0);
and now there is:
extern const pin_obj_t pin_A0_obj;
#define pin_A0 (&pin_A0_obj)
#define pyb_pin_X1 pin_A0
...
mp_hal_pin_high(pin_A0);
This patch should have minimal effect on board configuration files. The
only change that may be needed is if a board has .c files that configure
pins.
genhdr/pins.h is an internal header file that defines all of the pin
objects and it's cleaner to have pin.h include it (where the struct's for
these objects are defined) rather than an explicit include by every user.
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.
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.
