GPIO & RTC GPIO

Overview

The ESP32-C3 chip features 22 physical GPIO pads. Some GPIO pads cannot be used or do not have the corresponding pin on the chip package. For more details, see ESP32-C3 Technical Reference Manual > IO MUX and GPIO Matrix (GPIO, IO_MUX) [PDF]. Each pad can be used as a general purpose I/O or can be connected to an internal peripheral signal.

  • Note that GPIO12-17 are usually used for SPI flash.

  • Note that GPIO 18 and 19 are used by USB-JTAG by default. In order to use them as GPIOs, USB-JTAG will be disabled by the drivers.

  • ESP32-C3 doesn’t have separate “RTC GPIO” support. However, GPIO0-5 keep the rtc feature, which can be used for power-management and analog subsystem.

Application Example

GPIO output and input interrupt example: peripherals/gpio/generic_gpio.

API Reference - Normal GPIO

Functions

esp_err_t gpio_config(const gpio_config_t *pGPIOConfig)

GPIO common configuration.

Configure GPIO’s Mode,pull-up,PullDown,IntrType

Return

  • ESP_OK success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • pGPIOConfig: Pointer to GPIO configure struct

esp_err_t gpio_reset_pin(gpio_num_t gpio_num)

Reset an gpio to default state (select gpio function, enable pullup and disable input and output).

Note

This function also configures the IOMUX for this pin to the GPIO function, and disconnects any other peripheral output configured via GPIO Matrix.

Return

Always return ESP_OK.

Parameters
  • gpio_num: GPIO number.

esp_err_t gpio_set_intr_type(gpio_num_t gpio_num, gpio_int_type_t intr_type)

GPIO set interrupt trigger type.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number. If you want to set the trigger type of e.g. of GPIO16, gpio_num should be GPIO_NUM_16 (16);

  • intr_type: Interrupt type, select from gpio_int_type_t

esp_err_t gpio_intr_enable(gpio_num_t gpio_num)

Enable GPIO module interrupt signal.

Note

Please do not use the interrupt of GPIO36 and GPIO39 when using ADC or Wi-Fi with sleep mode enabled. Please refer to the comments of adc1_get_raw. Please refer to section 3.11 of ‘ECO_and_Workarounds_for_Bugs_in_ESP32’ for the description of this issue. As a workaround, call adc_power_acquire() in the app. This will result in higher power consumption (by ~1mA), but will remove the glitches on GPIO36 and GPIO39.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number. If you want to enable an interrupt on e.g. GPIO16, gpio_num should be GPIO_NUM_16 (16);

esp_err_t gpio_intr_disable(gpio_num_t gpio_num)

Disable GPIO module interrupt signal.

Return

  • ESP_OK success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number. If you want to disable the interrupt of e.g. GPIO16, gpio_num should be GPIO_NUM_16 (16);

esp_err_t gpio_set_level(gpio_num_t gpio_num, uint32_t level)

GPIO set output level.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG GPIO number error

Parameters
  • gpio_num: GPIO number. If you want to set the output level of e.g. GPIO16, gpio_num should be GPIO_NUM_16 (16);

  • level: Output level. 0: low ; 1: high

int gpio_get_level(gpio_num_t gpio_num)

GPIO get input level.

Warning

If the pad is not configured for input (or input and output) the returned value is always 0.

Return

  • 0 the GPIO input level is 0

  • 1 the GPIO input level is 1

Parameters
  • gpio_num: GPIO number. If you want to get the logic level of e.g. pin GPIO16, gpio_num should be GPIO_NUM_16 (16);

esp_err_t gpio_set_direction(gpio_num_t gpio_num, gpio_mode_t mode)

GPIO set direction.

Configure GPIO direction,such as output_only,input_only,output_and_input

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG GPIO error

Parameters
  • gpio_num: Configure GPIO pins number, it should be GPIO number. If you want to set direction of e.g. GPIO16, gpio_num should be GPIO_NUM_16 (16);

  • mode: GPIO direction

esp_err_t gpio_set_pull_mode(gpio_num_t gpio_num, gpio_pull_mode_t pull)

Configure GPIO pull-up/pull-down resistors.

Only pins that support both input & output have integrated pull-up and pull-down resistors. Input-only GPIOs 34-39 do not.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG : Parameter error

Parameters
  • gpio_num: GPIO number. If you want to set pull up or down mode for e.g. GPIO16, gpio_num should be GPIO_NUM_16 (16);

  • pull: GPIO pull up/down mode.

esp_err_t gpio_wakeup_enable(gpio_num_t gpio_num, gpio_int_type_t intr_type)

Enable GPIO wake-up function.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number.

  • intr_type: GPIO wake-up type. Only GPIO_INTR_LOW_LEVEL or GPIO_INTR_HIGH_LEVEL can be used.

esp_err_t gpio_wakeup_disable(gpio_num_t gpio_num)

Disable GPIO wake-up function.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number

esp_err_t gpio_isr_register(void (*fn)(void *), void *arg, int intr_alloc_flags, gpio_isr_handle_t *handle, )

Register GPIO interrupt handler, the handler is an ISR. The handler will be attached to the same CPU core that this function is running on.

This ISR function is called whenever any GPIO interrupt occurs. See the alternative gpio_install_isr_service() and gpio_isr_handler_add() API in order to have the driver support per-GPIO ISRs.

To disable or remove the ISR, pass the returned handle to the interrupt allocation functions.

Parameters
  • fn: Interrupt handler function.

  • arg: Parameter for handler function

  • intr_alloc_flags: Flags used to allocate the interrupt. One or multiple (ORred) ESP_INTR_FLAG_* values. See esp_intr_alloc.h for more info.

  • handle: Pointer to return handle. If non-NULL, a handle for the interrupt will be returned here.

Return

  • ESP_OK Success ;

  • ESP_ERR_INVALID_ARG GPIO error

  • ESP_ERR_NOT_FOUND No free interrupt found with the specified flags

esp_err_t gpio_pullup_en(gpio_num_t gpio_num)

Enable pull-up on GPIO.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number

esp_err_t gpio_pullup_dis(gpio_num_t gpio_num)

Disable pull-up on GPIO.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number

esp_err_t gpio_pulldown_en(gpio_num_t gpio_num)

Enable pull-down on GPIO.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number

esp_err_t gpio_pulldown_dis(gpio_num_t gpio_num)

Disable pull-down on GPIO.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number

esp_err_t gpio_install_isr_service(int intr_alloc_flags)

Install the driver’s GPIO ISR handler service, which allows per-pin GPIO interrupt handlers.

This function is incompatible with gpio_isr_register() - if that function is used, a single global ISR is registered for all GPIO interrupts. If this function is used, the ISR service provides a global GPIO ISR and individual pin handlers are registered via the gpio_isr_handler_add() function.

Return

  • ESP_OK Success

  • ESP_ERR_NO_MEM No memory to install this service

  • ESP_ERR_INVALID_STATE ISR service already installed.

  • ESP_ERR_NOT_FOUND No free interrupt found with the specified flags

  • ESP_ERR_INVALID_ARG GPIO error

Parameters
  • intr_alloc_flags: Flags used to allocate the interrupt. One or multiple (ORred) ESP_INTR_FLAG_* values. See esp_intr_alloc.h for more info.

void gpio_uninstall_isr_service(void)

Uninstall the driver’s GPIO ISR service, freeing related resources.

esp_err_t gpio_isr_handler_add(gpio_num_t gpio_num, gpio_isr_t isr_handler, void *args)

Add ISR handler for the corresponding GPIO pin.

Call this function after using gpio_install_isr_service() to install the driver’s GPIO ISR handler service.

The pin ISR handlers no longer need to be declared with IRAM_ATTR, unless you pass the ESP_INTR_FLAG_IRAM flag when allocating the ISR in gpio_install_isr_service().

This ISR handler will be called from an ISR. So there is a stack size limit (configurable as “ISR stack size” in menuconfig). This limit is smaller compared to a global GPIO interrupt handler due to the additional level of indirection.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_STATE Wrong state, the ISR service has not been initialized.

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number

  • isr_handler: ISR handler function for the corresponding GPIO number.

  • args: parameter for ISR handler.

esp_err_t gpio_isr_handler_remove(gpio_num_t gpio_num)

Remove ISR handler for the corresponding GPIO pin.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_STATE Wrong state, the ISR service has not been initialized.

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number

esp_err_t gpio_set_drive_capability(gpio_num_t gpio_num, gpio_drive_cap_t strength)

Set GPIO pad drive capability.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number, only support output GPIOs

  • strength: Drive capability of the pad

esp_err_t gpio_get_drive_capability(gpio_num_t gpio_num, gpio_drive_cap_t *strength)

Get GPIO pad drive capability.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number, only support output GPIOs

  • strength: Pointer to accept drive capability of the pad

esp_err_t gpio_hold_en(gpio_num_t gpio_num)

Enable gpio pad hold function.

The gpio pad hold function works in both input and output modes, but must be output-capable gpios. If pad hold enabled: in output mode: the output level of the pad will be force locked and can not be changed. in input mode: the input value read will not change, regardless the changes of input signal.

The state of digital gpio cannot be held during Deep-sleep, and it will resume the hold function when the chip wakes up from Deep-sleep. If the digital gpio also needs to be held during Deep-sleep, gpio_deep_sleep_hold_en should also be called.

Power down or call gpio_hold_dis will disable this function.

Return

  • ESP_OK Success

  • ESP_ERR_NOT_SUPPORTED Not support pad hold function

Parameters
  • gpio_num: GPIO number, only support output-capable GPIOs

esp_err_t gpio_hold_dis(gpio_num_t gpio_num)

Disable gpio pad hold function.

When the chip is woken up from Deep-sleep, the gpio will be set to the default mode, so, the gpio will output the default level if this function is called. If you don’t want the level changes, the gpio should be configured to a known state before this function is called. e.g. If you hold gpio18 high during Deep-sleep, after the chip is woken up and gpio_hold_dis is called, gpio18 will output low level(because gpio18 is input mode by default). If you don’t want this behavior, you should configure gpio18 as output mode and set it to hight level before calling gpio_hold_dis.

Return

  • ESP_OK Success

  • ESP_ERR_NOT_SUPPORTED Not support pad hold function

Parameters
  • gpio_num: GPIO number, only support output-capable GPIOs

void gpio_deep_sleep_hold_en(void)

Enable all digital gpio pad hold function during Deep-sleep.

When the chip is in Deep-sleep mode, all digital gpio will hold the state before sleep, and when the chip is woken up, the status of digital gpio will not be held. Note that the pad hold feature only works when the chip is in Deep-sleep mode, when not in sleep mode, the digital gpio state can be changed even you have called this function.

Power down or call gpio_hold_dis will disable this function, otherwise, the digital gpio hold feature works as long as the chip enter Deep-sleep.

void gpio_deep_sleep_hold_dis(void)

Disable all digital gpio pad hold function during Deep-sleep.

void gpio_iomux_in(uint32_t gpio_num, uint32_t signal_idx)

Set pad input to a peripheral signal through the IOMUX.

Parameters
  • gpio_num: GPIO number of the pad.

  • signal_idx: Peripheral signal id to input. One of the *_IN_IDX signals in soc/gpio_sig_map.h.

void gpio_iomux_out(uint8_t gpio_num, int func, bool oen_inv)

Set peripheral output to an GPIO pad through the IOMUX.

Parameters
  • gpio_num: gpio_num GPIO number of the pad.

  • func: The function number of the peripheral pin to output pin. One of the FUNC_X_* of specified pin (X) in soc/io_mux_reg.h.

  • oen_inv: True if the output enable needs to be inverted, otherwise False.

esp_err_t gpio_force_hold_all(void)

Force hold digital and rtc gpio pad.

Note

GPIO force hold, whether the chip in sleep mode or wakeup mode.

esp_err_t gpio_force_unhold_all(void)

Force unhold digital and rtc gpio pad.

Note

GPIO force unhold, whether the chip in sleep mode or wakeup mode.

esp_err_t gpio_sleep_sel_en(gpio_num_t gpio_num)

Enable SLP_SEL to change GPIO status automantically in lightsleep.

Return

  • ESP_OK Success

Parameters
  • gpio_num: GPIO number of the pad.

esp_err_t gpio_sleep_sel_dis(gpio_num_t gpio_num)

Disable SLP_SEL to change GPIO status automantically in lightsleep.

Return

  • ESP_OK Success

Parameters
  • gpio_num: GPIO number of the pad.

esp_err_t gpio_sleep_set_direction(gpio_num_t gpio_num, gpio_mode_t mode)

GPIO set direction at sleep.

Configure GPIO direction,such as output_only,input_only,output_and_input

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG GPIO error

Parameters
  • gpio_num: Configure GPIO pins number, it should be GPIO number. If you want to set direction of e.g. GPIO16, gpio_num should be GPIO_NUM_16 (16);

  • mode: GPIO direction

esp_err_t gpio_sleep_set_pull_mode(gpio_num_t gpio_num, gpio_pull_mode_t pull)

Configure GPIO pull-up/pull-down resistors at sleep.

Only pins that support both input & output have integrated pull-up and pull-down resistors. Input-only GPIOs 34-39 do not.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG : Parameter error

Parameters
  • gpio_num: GPIO number. If you want to set pull up or down mode for e.g. GPIO16, gpio_num should be GPIO_NUM_16 (16);

  • pull: GPIO pull up/down mode.

esp_err_t gpio_deep_sleep_wakeup_enable(gpio_num_t gpio_num, gpio_int_type_t intr_type)

Enable GPIO deep-sleep wake-up function.

Note

Called by the SDK. User shouldn’t call this directly in the APP.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number.

  • intr_type: GPIO wake-up type. Only GPIO_INTR_LOW_LEVEL or GPIO_INTR_HIGH_LEVEL can be used.

esp_err_t gpio_deep_sleep_wakeup_disable(gpio_num_t gpio_num)

Disable GPIO deep-sleep wake-up function.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • gpio_num: GPIO number

Macros

GPIO_PIN_COUNT
GPIO_IS_VALID_GPIO(gpio_num)

Check whether it is a valid GPIO number.

GPIO_IS_VALID_OUTPUT_GPIO(gpio_num)

Check whether it can be a valid GPIO number of output mode.

GPIO_IS_DEEP_SLEEP_WAKEUP_VALID_GPIO(gpio_num)

Type Definitions

typedef intr_handle_t gpio_isr_handle_t

Structures

struct gpio_config_t

Configuration parameters of GPIO pad for gpio_config function.

Public Members

uint64_t pin_bit_mask

GPIO pin: set with bit mask, each bit maps to a GPIO

gpio_mode_t mode

GPIO mode: set input/output mode

gpio_pullup_t pull_up_en

GPIO pull-up

gpio_pulldown_t pull_down_en

GPIO pull-down

gpio_int_type_t intr_type

GPIO interrupt type

Macros

GPIO_SEL_0

Pin 0 selected

GPIO_SEL_1

Pin 1 selected

GPIO_SEL_2

Pin 2 selected

GPIO_SEL_3

Pin 3 selected

GPIO_SEL_4

Pin 4 selected

GPIO_SEL_5

Pin 5 selected

GPIO_SEL_6

Pin 6 selected

GPIO_SEL_7

Pin 7 selected

GPIO_SEL_8

Pin 8 selected

GPIO_SEL_9

Pin 9 selected

GPIO_SEL_10

Pin 10 selected

GPIO_SEL_11

Pin 11 selected

GPIO_SEL_12

Pin 12 selected

GPIO_SEL_13

Pin 13 selected

GPIO_SEL_14

Pin 14 selected

GPIO_SEL_15

Pin 15 selected

GPIO_SEL_16

Pin 16 selected

GPIO_SEL_17

Pin 17 selected

GPIO_SEL_18

Pin 18 selected

GPIO_SEL_19

Pin 19 selected

GPIO_SEL_20

Pin 20 selected

GPIO_SEL_21

Pin 21 selected

GPIO_SEL_26

Pin 26 selected

GPIO_SEL_27

Pin 27 selected

GPIO_SEL_28

Pin 28 selected

GPIO_SEL_29

Pin 29 selected

GPIO_SEL_30

Pin 30 selected

GPIO_SEL_31

Pin 31 selected

GPIO_SEL_32

Pin 32 selected

GPIO_SEL_33

Pin 33 selected

GPIO_SEL_34

Pin 34 selected

GPIO_SEL_35

Pin 35 selected

GPIO_SEL_36

Pin 36 selected

GPIO_SEL_37

Pin 37 selected

GPIO_SEL_38

Pin 38 selected

GPIO_SEL_39

Pin 39 selected

GPIO_PIN_REG_0
GPIO_PIN_REG_1
GPIO_PIN_REG_2
GPIO_PIN_REG_3
GPIO_PIN_REG_4
GPIO_PIN_REG_5
GPIO_PIN_REG_6
GPIO_PIN_REG_7
GPIO_PIN_REG_8
GPIO_PIN_REG_9
GPIO_PIN_REG_10
GPIO_PIN_REG_11
GPIO_PIN_REG_12
GPIO_PIN_REG_13
GPIO_PIN_REG_14
GPIO_PIN_REG_15
GPIO_PIN_REG_16
GPIO_PIN_REG_17
GPIO_PIN_REG_18
GPIO_PIN_REG_19
GPIO_PIN_REG_20
GPIO_PIN_REG_21
GPIO_PIN_REG_22
GPIO_PIN_REG_23
GPIO_PIN_REG_24
GPIO_PIN_REG_25
GPIO_PIN_REG_26
GPIO_PIN_REG_27
GPIO_PIN_REG_28
GPIO_PIN_REG_29
GPIO_PIN_REG_30
GPIO_PIN_REG_31
GPIO_PIN_REG_32
GPIO_PIN_REG_33
GPIO_PIN_REG_34
GPIO_PIN_REG_35
GPIO_PIN_REG_36
GPIO_PIN_REG_37
GPIO_PIN_REG_38
GPIO_PIN_REG_39
GPIO_PIN_REG_40
GPIO_PIN_REG_41
GPIO_PIN_REG_42
GPIO_PIN_REG_43
GPIO_PIN_REG_44
GPIO_PIN_REG_45
GPIO_PIN_REG_46
GPIO_PIN_REG_47

Type Definitions

typedef void (*gpio_isr_t)(void *)

Enumerations

enum gpio_port_t

Values:

GPIO_PORT_0 = 0
GPIO_PORT_MAX
enum gpio_num_t

Values:

GPIO_NUM_NC = -1

Use to signal not connected to S/W

GPIO_NUM_0 = 0

GPIO0, input and output

GPIO_NUM_1 = 1

GPIO1, input and output

GPIO_NUM_2 = 2

GPIO2, input and output

GPIO_NUM_3 = 3

GPIO3, input and output

GPIO_NUM_4 = 4

GPIO4, input and output

GPIO_NUM_5 = 5

GPIO5, input and output

GPIO_NUM_6 = 6

GPIO6, input and output

GPIO_NUM_7 = 7

GPIO7, input and output

GPIO_NUM_8 = 8

GPIO8, input and output

GPIO_NUM_9 = 9

GPIO9, input and output

GPIO_NUM_10 = 10

GPIO10, input and output

GPIO_NUM_11 = 11

GPIO11, input and output

GPIO_NUM_12 = 12

GPIO12, input and output

GPIO_NUM_13 = 13

GPIO13, input and output

GPIO_NUM_14 = 14

GPIO14, input and output

GPIO_NUM_15 = 15

GPIO15, input and output

GPIO_NUM_16 = 16

GPIO16, input and output

GPIO_NUM_17 = 17

GPIO17, input and output

GPIO_NUM_18 = 18

GPIO18, input and output

GPIO_NUM_19 = 19

GPIO19, input and output

GPIO_NUM_20 = 20

GPIO20, input and output

GPIO_NUM_21 = 21

GPIO21, input and output

GPIO_NUM_22 = 22

GPIO22, input and output

GPIO_NUM_MAX
enum gpio_int_type_t

Values:

GPIO_INTR_DISABLE = 0

Disable GPIO interrupt

GPIO_INTR_POSEDGE = 1

GPIO interrupt type : rising edge

GPIO_INTR_NEGEDGE = 2

GPIO interrupt type : falling edge

GPIO_INTR_ANYEDGE = 3

GPIO interrupt type : both rising and falling edge

GPIO_INTR_LOW_LEVEL = 4

GPIO interrupt type : input low level trigger

GPIO_INTR_HIGH_LEVEL = 5

GPIO interrupt type : input high level trigger

GPIO_INTR_MAX
enum gpio_mode_t

Values:

GPIO_MODE_DISABLE = GPIO_MODE_DEF_DISABLE

GPIO mode : disable input and output

GPIO_MODE_INPUT = GPIO_MODE_DEF_INPUT

GPIO mode : input only

GPIO_MODE_OUTPUT = GPIO_MODE_DEF_OUTPUT

GPIO mode : output only mode

GPIO_MODE_OUTPUT_OD = ((GPIO_MODE_DEF_OUTPUT) | (GPIO_MODE_DEF_OD))

GPIO mode : output only with open-drain mode

GPIO_MODE_INPUT_OUTPUT_OD = ((GPIO_MODE_DEF_INPUT) | (GPIO_MODE_DEF_OUTPUT) | (GPIO_MODE_DEF_OD))

GPIO mode : output and input with open-drain mode

GPIO_MODE_INPUT_OUTPUT = ((GPIO_MODE_DEF_INPUT) | (GPIO_MODE_DEF_OUTPUT))

GPIO mode : output and input mode

enum gpio_pullup_t

Values:

GPIO_PULLUP_DISABLE = 0x0

Disable GPIO pull-up resistor

GPIO_PULLUP_ENABLE = 0x1

Enable GPIO pull-up resistor

enum gpio_pulldown_t

Values:

GPIO_PULLDOWN_DISABLE = 0x0

Disable GPIO pull-down resistor

GPIO_PULLDOWN_ENABLE = 0x1

Enable GPIO pull-down resistor

enum gpio_pull_mode_t

Values:

GPIO_PULLUP_ONLY

Pad pull up

GPIO_PULLDOWN_ONLY

Pad pull down

GPIO_PULLUP_PULLDOWN

Pad pull up + pull down

GPIO_FLOATING

Pad floating

enum gpio_drive_cap_t

Values:

GPIO_DRIVE_CAP_0 = 0

Pad drive capability: weak

GPIO_DRIVE_CAP_1 = 1

Pad drive capability: stronger

GPIO_DRIVE_CAP_2 = 2

Pad drive capability: medium

GPIO_DRIVE_CAP_DEFAULT = 2

Pad drive capability: medium

GPIO_DRIVE_CAP_3 = 3

Pad drive capability: strongest

GPIO_DRIVE_CAP_MAX