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_LP_PERIPHERALS_SUPPORTED
There is also separate "RTC GPIO" support, which functions when GPIOs are routed to the "RTC" low-power, analog subsystem, and Low-Power(LP) peripherals. These pin functions can be used when:
..list::
- In Deep-sleep mode
:SOC_ULP_FSM_SUPPORTED:- The :doc:`Ultra Low Power FSM co-processor <../../api-reference/system/ulp>` is running
:SOC_RISCV_COPROC_SUPPORTED:- The :doc:`Ultra Low Power RISC-V co-processor <../../api-reference/system/ulp-risc-v>` is running
:SOC_LP_CORE_SUPPORTED:- The :doc:`Ultra Low Power LP-Core co-processor <../../api-reference/system/ulp-lp-core>` is running
- Analog functions such as ADC/DAC/etc are in use
:SOC_LP_PERIPHERALS_SUPPORTED:- LP peripherals, such as LP_UART, LP_I2C, are in use
- As a simple GPIO input to read the level on the pin, or as a simple GPIO output to output the desired level on the pin.
- As a peripheral signal input/output.
IDF peripheral drivers always take care of the necessary IO configurations that need to be applied onto the pins, so that they can be used as the peripheral signal inputs or outputs. This means the users usually only need to be responsible for configuring the IOs as simple inputs or outputs. :cpp:func:`gpio_config` is an all-in-one API that can be used to configure the I/O mode, internal pull-up/pull-down resistors, etc. for pins.
In some applications, an IO pin can serve dual purposes. For example, the IO, which outputs a LEDC PWM signal, can also act as a GPIO input to generate interrupts or GPIO ETM events. Careful handling on the configuration step is necessary for such dual use of IO pins cases. :cpp:func:`gpio_config` is an API that overwrites all the current configurations, so it must be called to set the pin mode to :cpp:enumerator:`gpio_mode_t::GPIO_MODE_INPUT` before calling the LEDC driver API which connects the output signal to the pin. As an alternative, if no other configuration is needed other than making the pin input enabled, :cpp:func:`gpio_input_enable` can be the one to call at any time to achieve the same purpose.
GPIO driver offers a dump function :cpp:func:`gpio_dump_io_configuration` to show the current configurations of IOs, such as pull-up/pull-down, input/output enable, pin mapping, etc. Below is an example of how to dump the configuration of GPIO4, GPIO18, and GPIO26:
If an IO pin is routed to a peripheral signal through the GPIO matrix, the signal ID printed in the dump information is defined in the :component_file:`soc/{IDF_TARGET_PATH_NAME}/include/soc/gpio_sig_map.h` header file. The word ``**RESERVED**`` indicates the IO is occupied by either SPI flash or PSRAM. It is strongly not recommended to reconfigure them for other application purposes.
Do not rely on the default configurations values in the Technical Reference Manual, because it may be changed in the bootloader or application startup code before app_main.
To configure the USB PHY pins to GPIO, you can use the function :cpp:func:`gpio_config`. Below is an example of how to configure the USB PHY pins to GPIO:
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 does not 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::gpio_num` sets the GPIO that will be applied to the flex glitch filter.
-: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 not 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`.
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`.
*:example:`peripherals/gpio/generic_gpio` demonstrates how to configure GPIO to generate pulses and use it with interruption.
:esp32s2:* :example:`peripherals/gpio/matrix_keyboard` demonstrates how to drive a common matrix keyboard using the dedicated GPIO APIs, including manipulating the level on a group of GPIOs, triggering edge interrupt, and reading level on a group of GPIOs.
