Currently, spi_acquire() will always re-configure the SPI bus.
If the configuration did not change, this is entirely uneccecary
and makes SPI operations take longer than needed.
Instead, compare the current configuration with the new configuration
and skip the initialisation if it didn't change since the last call.
The RTC expects to be clocked from a 1kHz source.
Previously it would re-configure GCLK2 from 32kHz to 1kHz when used.
Since GCLK2 is also used by EIC, this would break external interrupts
in strange and unexpected ways.
Dedicate a 1kHz clock to it to avoid the damage.
From the data sheet:
> The COUNT register requires synchronization when reading.
> Disabling the synchronization will prevent reading valid
> values from the COUNT register.
Without this bit enabled, rtt_get_counter() will always return 0.
ATmega128RFA1/ATmega256RFR2 do not have a unique CPU ID.
Use the RC oscillator callibration byte as an impromptu CPU ID and rely
on bootlader constants present on all ATmega families for the remaining
bytes.
This way we can provide a faux CPU ID on all ATmega MCUs and typical hobbyists
with no access to JTAG adapters or high voltage programmer capable of writing
the user signature have a good chance that the CPU IDs of their device do not collide.
This converts the hard-coded UART driver to the new ways.
- allow the board to configure the RX & TX pins
- allow for more than one UART
- allow setting the baudrate
- implement poweron()/poweroff() functions
Currently the cpu/lpc2387 init code hard-codes a 16 MHz
external oscillator.
Instead, calculate the PLL multiplier based on the board define
and also allow to run without an external oscillator.
Scan-build detected that sercom_id could return -1 and the value of this function is affected to uint8_t variables. Since these variables are used for shitfing bit in registers, this could lead to undefined behavior
Fix the condition to return -ENOPNOTSUPP when i2c repeated read attempted.
Currently the error occures even if a read after write is attempted.
This is the standard way to i2c_read_reg which should be supported.
The -EOPNOTSUPP requires the previous R/W state to be reading.
This means a `I2C_SR2_TRA` must be checked to be 0.
There is no hardware limitation for custom boards based on STM32 to uses
SPI bus with signals coming from different PORT and alternate functions.
This patch allow alternate's function definition per pin basis, thus enable
the support of SPI bus signals routed on differents PORT.
Signed-off-by: Yannick Gicquel <ygicquel@gmail.com>
