There is also separate "RTC GPIO" support, which functions when GPIOs are routed to the "RTC" low-power and analog subsystem. These pin functions can be used when:
..only:: SOC_GPIO_SUPPORT_PIN_GLITCH_FILTER or SOC_GPIO_FLEX_GLITCH_FILTER_NUM
GPIO Glitch Filter
------------------
The {IDF_TARGET_NAME} chip features hardware filters to remove unwanted glitch pulses from the input GPIO, which can help reduce false triggering of the interrupt and prevent a noise being routed to the peripheral side.
Each GPIO can be configured with a glitch filter, which can be used to filter out pulses shorter than **two** sample clock cycles. The duration of the filter is not configurable. The sample clock is the clock source of the IO_MUX. In the driver, we call this kind of filter as ``pin glitch filter``. You can create the filter handle by calling :cpp:func:`gpio_new_pin_glitch_filter`. All the configurations for a pin glitch filter are listed in the :cpp:type:`gpio_pin_glitch_filter_config_t` structure.
{IDF_TARGET_NAME} provides {IDF_TARGET_FLEX_GLITCH_FILTER_NUM} flexible glitch filters, whose duration is configurable. We refer to this kind of filter as ``flex flitch filter``. Each of them can be applied to any input GPIO. However, applying multiple filters to the same GPIO doesn't make difference from one. You can create the filter handle by calling :cpp:func:`gpio_new_flex_glitch_filter`. All the configurations for a flexible glitch filter are listed in the :cpp:type:`gpio_flex_glitch_filter_config_t` structure.
-:cpp:member:`gpio_flex_glitch_filter_config_t::window_width_ns` and :cpp:member:`gpio_flex_glitch_filter_config_t::window_thres_ns` are the key parameters of the glitch filter. During :cpp:member:`gpio_flex_glitch_filter_config_t::window_width_ns`, any pulse whose width is shorter than :cpp:member:`gpio_flex_glitch_filter_config_t::window_thres_ns` will be discarded. Please note that, you can't set :cpp:member:`gpio_flex_glitch_filter_config_t::window_thres_ns` bigger than :cpp:member:`gpio_flex_glitch_filter_config_t::window_width_ns`.
.. only:: SOC_GPIO_SUPPORT_PIN_GLITCH_FILTER and SOC_GPIO_FLEX_GLITCH_FILTER_NUM
The glitch filter is disabled by default, and can be enabled by calling :cpp:func:`gpio_glitch_filter_enable`. To recycle the filter, you can call :cpp:func:`gpio_del_glitch_filter`. Please note, before deleting the filter, you should disable it first by calling :cpp:func:`gpio_glitch_filter_disable`.
{IDF_TARGET_NAME} support the hardware hysteresis of the input pin, which can reduce the GPIO interrupt shoot by accident due to unstable sampling when the input voltage is near the criteria of logic 0 and 1, especially when the input logic level conversion is slow or the voltage setup time is too long.
Each pin can enable hysteresis function independently. By default, it controlled by eFuse and been closed, but it can also be enabled or disabled by software manually. You can select the hysteresis control mode by configuring :cpp:member:`gpio_config_t::hys_ctrl_mode`. Hysteresis control mode is set along with all the other GPIO configurations in :cpp:func:`gpio_config`.
When the hysteresis function is controlled by eFuse, this feature can still be controlled independently for each pin, you need to `burn the eFuse <https://docs.espressif.com/projects/esptool/en/latest/esp32/espefuse/index.html>`_ to enable the hysteresis function on specific GPIO additionally.
..only:: not SOC_GPIO_SUPPORT_PIN_HYS_CTRL_BY_EFUSE
Each pin can enable hysteresis function independently. By default, the function is not enabled. You can select the hysteresis control mode by configuring :cpp:member:`gpio_config_t::hys_ctrl_mode`. Hysteresis control mode is set along with all the other GPIO configurations in :cpp:func:`gpio_config`.
