This removes the difference in the time.ticks_us() range between SAMD21 and
SAMD51.
The function mp_hal_ticks_us_64() is added and used for:
- SAMD51's mp_hal_ticks_us and mp_hal_delay_us().
For SAMD21, keep the previous methods, which are faster.
- mp_hal_ticks_ms() and mp_hal_tick_ms_64(), which saves some bytes
and removes a potential race condition every 50 days.
Also set the us-counter for SAMD51 to 16 MHz for a faster reading of the
microsecond value.
Note: With SAMD51, mp_hal_ticks_us_64() has a 60 bit range only, which is
still a long time (~36000 years).
Methods implemented are:
- rtc.init(date)
- rtc.datetime([new_date])
- rtc.calibration(value)
The presence of this class can be controlled by MICROPY_PY_MACHINE_RTC. If
the RTC module is used, the time module uses the RTC as well.
For boards without a 32kHz crystal, using RTC makes no sense, since it will
then use the ULP32K oscillator, which is not precise at all. Therefore, it
will by default only be enabled for boards using a crystal, but can be
enabled in the respective mpconfigboard.h.
Tested with a SD card connected to a SAMD51 board. The SEEED WIO terminal
has a SD-Card reader built-in.
Also a side change to remove a few obsolete lines from Makefile.
The range is 1MHz - 48 MHz. Note that below 8 MHz there is no USB support.
The frequency will be set to an integer fraction of 48 MHz. And after
changing the frequency, the peripherals like PWM, UART, I2C, SPI have to be
reconfigured.
Current consumption e.g. of the Seeed Xiao board at 1 MHz is about 1.5 mA,
mostly caused by the on-board LED (green LED with 1k resistor at 3.3V).
Changes are:
- Set the feature level for each MCU: CORE features for SAMD21, and EXTRA
features for SAMD51.
- Remove all definitions that are included in the core feature level.
- Keep the default settings for feature level and float, to make the choice
obvious.
It can be enabled/disabled by a configuration switch. The code size
increase is 308 bytes, but it requires RAM space for buffers, the larger
UART object and root pointers.
