Adds a memset function `system_secure_memset` which cannot be optimized out by the compiler. It uses the libsodium approach of weak symbols. Function system_secure_memset calls the standard memset. Calling an empty function declared with weak attribute after the memset call, prevents the compiler to optimize it out. The overhead is only one function call.
Although ESP32 has four SPI controllers, only two of them can be effectively used (HSP and VSPI). The third one (FSPI) is used for external memory such as flash and PSRAM and can not be used for peripherals. FSPI is therefore removed from the API. In addition, the SPI0_DEV and SPI1_DEV configuration parameters are renamed SPI0_CTRL and SPI1_CTRL to better describe what they define and to avoid confusion with SPI_DEV (0) and SPI_DEV (1).
Although ESP32 has four SPI controllers, only two of them can be effectively used (HSP and VSPI). The third one (FSPI) is used for external memory such as flash and PSRAM and can not be used for peripherals. FSPI is therefore removed from the API. In addition, the SPI0_DEV and SPI1_DEV configuration parameters are renamed SPI0_CTRL and SPI1_CTRL to better describe what they define and to avoid confusion with SPI_DEV (0) and SPI_DEV (1).
Timer restart was moved from esp_now_scan_peers_done to esp_now_scan_peers_start to avoid that the scan for peers isn't triggered anymore if the esp_now_scan_peers_done callback isn't called because of errors.
The brr calculation on the datasheet is different than what is implmented.
This is intentional since it provides better rounding due to truncation.
There was no comment explaining that so this comment should prevent confusion.
Since it is not possible to reenter the function `esp_now_recv_cb`, and the functions netif::_ recv and esp_now_netdev::_ recv are called directly in the same thread context we can read directly from the `buf` and don't need a receive buffer anymmore.
Since it is not possible to reenter the function `esp_now_recv_cb`, and the functions netif::_ recv and esp_now_netdev::_ recv are called directly in the same thread context we only need a buffer which contains one frame and its source mac address.
Since it is not possible to reenter the function `esp_now_recv_cb`, and the functions netif::_ recv and esp_now_netdev::_ recv are called directly in the same thread context, neither a mutual exclusion has to be realized nor have the interrupts to be deactivated.
Since the esp_now_recv_cb function is not called directly as an ISR through interrupts, it is not executed in the interrupt context. _recv can therefore be called directly. The treatment of the recv_event is no longer necessary.
Although it should not be possible to reenter the function esp_now_recv_cb, this is avoided by an additional boolean variable. It can not be realized by mutex because it would reenter from same thread context. If macro NDEBUG is not defined, an assertion is used.
A second slot is defined with a calculated size, from the
remaining flash after the bootloader and the first slot.
Both slots are defined as equal size, but it can be overriden.
