Espressif Systems ESP8684 Series, Hardware Design Manuallines, Page: 13 / 28

2 Schematic Checklist
Note:
The content below is excerpted from Section General Purpose Input / Output Interface (GPIO) in
ESP8684 Technical Reference Manual .
ESP8684 series has 14 GPIO pins which can be assigned various functions by configuring corresponding
registers. Besides digital signals, some GPIOs can be also used for analog functions, such as ADC.
All GPIOs have selectable internal pull-up or pull-down, or can be set to high impedance. When these GPIOs are
configured as an input, the input value can be read by software through the register. Input GPIOs can also be set
to generate edge-triggered or level-triggered CPU interrupts. All digital IO pins are bi-directional, non-inverting
and tristate, including input and output buffers with tristate control. These pins can be multiplexed with other
functions, such as the UART, SPI, etc. For low-power operations, the GPIOs can be set to holding state.
The IO MUX and the GPIO matrix are used to route signals from peripherals to GPIO pins. Together they provide
highly configurable I/O. Using GPIO Matrix, peripheral input signals can be configured from any IO pins while
peripheral output signals can be configured to any IO pins. Table 4 shows the IO MUX functions of each
pin.
For more information about IO MUX and GPIO matrix, please refer to Chapter IO MUX and GPIO Matrix (GPIO,
IO_MUX) in ESP8684 Technical Reference Manual .
Table 4: IO MUX Pin Functions
Pin Name No. Function 0 Function 1 Function 2 Reset Notes
GPIO0 4 GPIO0 GPIO0 — 0 R
GPIO1 5 GPIO1 GPIO1 — 0 R
GPIO2 6 GPIO2 GPIO2 FSPIQ 1 R
GPIO3 8 GPIO3 GPIO3 — 1 R
MTMS 9 MTMS GPIO4 FSPIHD 1 R
MTDI 10 MTDI GPIO5 FSPIWP 1 R
MTCK 12 MTCK GPIO6 FSPICLK 1* —
MTDO 13 MTDO GPIO7 FSPID 1 —
GPIO8 14 GPIO8 GPIO8 — 1 —
GPIO9 15 GPIO9 GPIO9 — 3 —
GPIO10 16 GPIO10 GPIO10 FSPICS0 1 —
GPIO18 18 GPIO18 GPIO18 — 0 —
U0RXD 19 U0RXD GPIO19 — 3 —
U0TXD 20 U0TXD GPIO20 — 4 —
Reset
The default configuration of each pin after reset:
•
0
- input disabled, in high impedance state (IE = 0)
•
1
- input enabled, in high impedance state (IE = 1)
•
2
- input enabled, pull-down resistor enabled (IE = 1, WPD = 1)
•
3
- input enabled, pull-up resistor enabled (IE = 1, WPU = 1)
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ESP8684 Series Hardware Design Guidelines v1.1