The former correction factors were determined by measuring the resulting clocks without a device connected to the bus.
However, when testing the changes for low CPU clock frequencies, it was figured out that the clocks not only depend on configured register values
_i2c_hw[dev].regs->scl_low_period.period
_i2c_hw[dev].regs->scl_high_period.period
but also on the bus capacity. Obviously, the register values are not absolute times in APB clock cycles, but rather times that start as soon as the corresponding level is reached. In this case, the higher the bus capacity, the longer the period would be.
This means that the clock speed cannot be precisely controlled via the correction factors anyway. For this reason, and because the I2C implementation in ESP-IDF also does not use correction factors, they were removed.
When entering a sleep mode, all wake-up sources should first be disabled before the wake-up sources required for the sleep mode are then stepwise enabled again. Otherwise, an wake-up configuration of one sleep mode may affect the wake-up within another sleep mode.
The WiFi interface should be stopped before reboot or sleep. But stopping the WiFi interface disconnects an existing connection. Usually, esp_wifi_netdev tries to reconnect on an disconnect event. However, trying reconnect with a stopped WiFi interface may lead to a crash. Therefore, the stop event has to be handled.
Now, where the vendor files for light/deep sleep mode are added, function `pm_off` does not need to implement this mode by itself. Instead the existing deep sleep with disabled wakeup sources is used for pm_off.
`rtc_init` is used after light sleep to update the system time from RTC timer. The fix corrects a small difference of about 230 ms which would sum up with each wakeup from light sleep.
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.
- 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 .
It is possible to use different timers as RTC timer for the periph_rtc module. Either the 48-bit RTC hardware timer is used directly or the PLL driven 64-bit system timer emulates a RTC timer. The latter one is much more accurate. Pseudomodule esp_rtc_timer controlls which timer is used. Only if esp_rtc_timer is enabled explicitly, the 48-bit RTC hardware timer is used. Otherwise the 64-bit sytstem timer is used to emulate the RTC timer.
Startup information, including board configuration, is only printed when module esp_log_startup is used. This reduces the amount of information that is printed by default to the console during the startup. The user can enable module esp_log_startup to get the additional startup information.
If `SPI_CS_UNDEF` is given as the `cs` parameter, CS pin must not be handled by the driver. Furthermore, if `cont` parameter is true, CS pin must not be disabled at the end of one transfer.
