- Add libstdcpp feature to indicate a platform is providing a libstdc++
implementation ready for use
- The existing cpp feature now only indicates a working C++ toolchain without
libstdc++. (E.g. still useful for the Arduino compatibility layer.)
- Added libstdcpp as required feature were needed
- Added some documentation on C++ on RIOT
>All of them are features of each ESP SoC and have not to be configured by the
board definition.
Signed-off-by: Jean Pierre Dudey <jeandudey@hotmail.com>
Co-authored-by: Gunar Schorcht <gunar@schorcht.net>
There are common features that can be used by ESP32 as well as ESP8266, for example the `esp_wifi` module. To be able to test for any ESP SoC, feature `arch_esp` is introduced.
Flashing an ESP board first requires the creation of a flash image from the ELF file. This is realized in the `preflash` target. However, the `preflash` target only depends on the variable `BUILD_BEFORE_FLASH` but on the ELF file. Therefore, the variable `BUILD_BEFORE_FLASH` must be set to the ELF file to ensure that when using multiple make processes, the compilation of the ELF file is completed before the flash image is created.
GPIO32 and GPIO33 are used during boot to start an 32.768 kHz XTAL if it is connected to these GPIOs. If the 32.768 kHz XTAL is not connected, these pins can be used digital IO. However, the 32.678 kHz XTAL has to be disabled explicitly in this case. Furthermore, the handling of GPIOs greater than GPIO31 had to be fixed in I2C software implementation.
Due to stability reasons, the SoftAP interface of the WiFi module was always enabled in former versions even if only the station interface was used. Therefore the WiFi modem had to be always active and the SoC could not enter the modem sleep mode. Therefore, the SoftAP interface is only enabled when ESP-NOW is used.
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.
To be able to define common configurations for all ESP CPUs, the CPU specific configuration cpu_conf.h has to include a common configuration. For that purpose cpu_conf.h in cpu/esp_common is renamed to cpu_conf_common.h and included in CPU specific configurations.
