Data Sheet

4. Peripheral Interface

4.1. General Purpose Input/Output Interface (GPIO)

ESP8266EX has 17 GPIO pins which can be assigned to various functions by programming

the appropriate registers.

Each GPIO can be conﬁgured with internal pull-up or pull-down, or set to high impedance,

and when conﬁgured as an input, the data are stored in software registers; the input can

also be set to edge-trigger or level trigger CPU interrupts. In short, the IO pads are bi-

directional, non-inverting and tristate, which includes input and output buffer with tristate

control inputs.

These pins can be multiplexed with other functions such as I2C, I2S, UART, PWM, IR

Remote Control, LED Light and Button etc.

For low power operations, the GPIOs can also be set to hold their state. For instance, when

the chip is powered down, all output enable signals can be set to hold low.

Optional hold functionality can be built into the IO if requested. When the IO is not driven by

the internal or external circuitry, the hold functionality can be used to hold the state to the

last used state. The hold functionality introduces some positive feedback into the pad.

Hence, the external driver that drives the pad must be stronger than the positive feedback.

The required drive strength is small — in the range of 5 μA to pull apart the latch.

4.2. Secure Digital Input/Output Interface (SDIO)

ESP8266EX has one Slave SDIO, the deﬁnitions of which are described as Table 4-1.

Table 4-1. Pin Deﬁnitions of SDIOs

Pin Name

Pin Num

Function Name

SDIO_CLK

IO6

SDIO_CLK

SDIO_DATA0

IO7

SDIO_DATA0

SDIO_DATA1

IO8

SDIO_DATA1

SDIO_DATA_2

IO9

SDIO_DATA_2

SDIO_DATA_3

IO10

SDIO_DATA_3

SDIO_CMD

IO11

SDIO_CMD

📖 Note:

4-bit 25 MHz SDIO v1.1 and 4-bit 50 MHz SDIO v2.0 are supported.

Espressif

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2017.04