Pin definition
ESP8266EX chip pinout is something like this:
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | VDDA | P | Analog Power 3.0 ~3.6V |
| 2 | LNA | I/O | RF Antenna Interface,Chip Output Impedance=50 Ω No matching required but we recommend that the π- type matching network is retained. |
| 3 | VDD3P3 | P | Amplifier Power 3.0~3.6V |
| 4 | VDD3P3 | P | Amplifier Power 3.0~3.6V |
| 5 | VDD_RTC | P | NC(1.1V) |
| 6 | TOUT | I | ADC Pin |
| 7 | CHIP_EN | I | Chip Enable. High: On, chip works properly; Low: Off, small current |
| 8 | XPD_DCDC | I/O | Deep-Sleep Wakeup;GPIO16 |
| 9 | MTMS | I/O | GPIO14; HSPICLK |
| 10 | MTDI | I/O | GPIO12;HSPIQ |
| 11 | VDDPST | P | Digital/IO Power Supply (1.8V~3.3V) |
| 12 | MTCK | I/O | GPIO13;HSPID |
| 13 | MTDO | I/O | GPIO15;HSPICS |
| 14 | GPIO2 | I/O | UART Tx during flash progamming; GPIO2 |
| 15 | GPIO0 | I/O | GPIO0;SPICS2 |
| 16 | GPIO4 | I/O | GPIO4 |
| 17 | VDDPST | P | Digital/IO Power Supply (1.8V~3.3V) |
| 18 | SDIO_DATA_2 | I/O | Connect to SD_D2 (Series R 200Ω);SPIHD; HSPIHD |
| 19 | SDIO_DATA_3 | I/O | Connect to SD_D3 (Series R 200Ω); SPIWP; HSPIWP |
| 20 | SDIO_CMD | I/O | Connect to SD_CMD(Series R 200Ω); SPICS0 |
| 21 | SDIO_CLK | I/O | Connect to SD_CLK (Series R 200Ω); SPICLK |
| 22 | SDIO_DATA_0 | I/O | Connect to SD_D0 (Series R 200Ω); SPIQ |
| 23 | SDIO_DATA_1 | I/O | Connect to SD_D1 (Series R 200Ω); SPID |
| 24 | GPIO5 | I/O | GPIO5 |
| 25 | U0RXD | I/O | UART Rx during flash progamming; GPIO3 |
| 26 | U0TXD | I/O | UART Tx during flash progamming; GPIO1; SPICS1 |
| 27 | XTAL_OUT | I/O | Connect to crystal output, can be used to provide BT clock input |
| 28 | XTAL_IN | I/O | Connect to crystal input |
| 29 | VDDD | P | Analog Power 3.0~3.6V |
| 30 | VDDA | P | Analog Power 3.0~3.6V |
| 31 | RES12K | I | Connect to series R 12kΩ to ground |
| 32 | EXT_RSTB | I | External reset signal (Low: Active) |
| Note: GPIO2, GPIO0, MTDO can be configurable as 3-bit SDIO mode |