By using a custom EPOCH for the RTC implementation, we can extend the
range of the 32 bit counter based RTC by 118 years.
It also reduces the code size compared to the stdlib based POSIX functions.
During the write access to the SPI flash, the IROM cache is not available and only code from the IRAM can be executed. Therefore, the code of file system implementations which access the SPI flash must reside in IRAM.
The same tool 'gen_esp32part.py' is used for the generation of partition tables on ESP8266 as well as n ESP32. The tool is therefore added to 'dist/tools/esptool'
With the new toolchain version required to fix issue #13133, the compilation of `examples/posix_socket` fails due to a C linkage error in `atomic_base.h`. The reason is that including `drivers/include/mtd.h` in `boards/esp32/board_common.h` inside the `extern C` block finally leads to including `atomic_base.h` inside the `extern C` block which in turn to the C linkage error for the template definitions in this file.
ESP32 can be clocked with either a 40 MHz or 26 MHz crystal. Since most boards use a 40 MHz crystal, the configuration was previously fixed to a 40 MHz crystal. This commit changes the crystal from 40 MHz to automatic detection, allowing boards with a 26 MHz crystal like the Sparkfun ESP32 Thing DEV to be used.
- Unecessary definitions are removed.
- Since the 48-bit RTC hardware timer uses a RC oscillator as clock, it is pretty inaccurate and leads to a RTC time deviation of up to 3 seconds per minute. Therefore, a calibration during the boot time determines a correction factor for the 48-bit RTC hardware timer. Function _rtc_time_to_us uses now this correction factor and converts a raw 48-bit RTC time to a corrected time in microseconds. Thus, the 48-bit RTC timer becomes much more accurate, but it can't still reach the accuracy of the PLL driven 64-bit system timer. The Advantage of using RTC over 64-bit sydtem timer is that it also continues in deep sleep mode and after software reset.
- If the 64-bit system timer is used to emulate the RTC timer, it uses the RTC hardware timer to continue its operation after software .
