The underlying peripheral can only read from RAM. This uses the
existing infrastructure (already needed to work around the lack of a
hardware support for I2C_NOSTART) to unconditionally copy any to-be-sent
data into RAM.
- Move common code for USART (shared SPI / UART peripheral) to its
own file and allow sharing the USART peripheral to provide both
UART and SPI in round-robin fashion.
- Configure both UART and SPI bus via a `struct` in the board's
`periph_conf.h`
- this allows allocating the two UARTs as needed by the use case
- since both USARTs signals have a fixed connection to a single
GPIO, most configuration is moved to the CPU
- the board now only needs to decide which bus is provided by
which USART
Note: Sharing an USART used as UART requires cooperation from the app:
- If the UART is used in TX-only mode (no RX callback), the driver
will release the USART while not sending
- If the UART is used to also receive, the application needs to power
the UART down while not expecting something to send. An
`spi_acquire()` will be blocked while the UART is powered up.
This commit optimizes the `gpio_conf_t` type in the following
regards:
- The "base" `gpio_conf_t` is stripped from members that only some
platforms support, e.g. drive strength, slew rate, and disabling of
the Schmitt Trigger are no longer universally available but
platform-specific extensions
- The `gpio_conf_t` is now crammed into a bit-field that is 8 bit or
16 bit wide. This allows for storing lots of them e.g. in
`driver_foo_params_t` or `uart_conf_t` etc.
- A `union` of the `struct` with bit-field members and a `bits` is used
to allow accessing all bits in a simple C statement and to ensure
alignment for efficient handling of the type
Co-authored-by: Gunar Schorcht <gunar@schorcht.net>
Expose the compile time configuration knob `CONFIG_AFIO_PCF0_SWJ_CFG`
to allow freeing some/all JTAG pins and use them as GPIOs.
As default, PB4 is remapped from NJTRST to be usable as regular GPIO.
This still allows using the JTAG interface for debugging/flashing,
but makes an GPIO exposed by some boards available.
The API doc clearly states that arbitrary high PWM frequencies can
be requested and the driver should reduce the frequency while keeping
the resolution, when required. So change the code to just do that
rather than blowing assertions.
The function configures additional features of the DMA stream for F2/F4/F7.
`dma_setup_ext` added to configure F2/F4/F7 specific additional features like `MBURST`, `PBURST`, `FIFO` and Peripheral flow controller. It is supposed to be used after `dma_setup` and `dma_prepare`.
timer_set has no documented restriction on this being not null, other
implementations explicitly tolerate it (rpx0xx checks inside the ISR,
but doing it at init time keeps the ISR slim).
This is useful when using a timer just to read, without any action when
it triggers (the action is taken depending on read values, eg. in a
thread context).
- boot the I2C after init in low power mode
- otherwise I2C will consume more power until the first time it is
used, which is surprising
- STM32 F1 only: reconfigure SCL and SDA as GPIOs while the I2C
peripheral is powered down
- When the I2C peripheral is not clocked, it drives SCL and SDA
down. This will dissipate power across the pull up resistor.
