| Label |
GPIO |
Input |
Output |
Notes |
| D0 |
GPIO16 |
no interrupt |
no PWM or I2C support |
HIGH at boot - used to wake up from deep sleep |
| D1 |
GPIO5 |
OK |
OK |
often used as SCL (I2C) |
| D2 |
GPIO4 |
OK |
OK |
often used as SDA (I2C) |
| D3 |
GPIO0 |
pulled up |
OK |
connected to FLASH button, boot fails if pulled LOW |
| D4 |
GPIO2 |
pulled up |
OK |
HIGH at boot - connected to on-board LED, boot fails if pulled LOW |
| D5 |
GPIO14 |
OK |
OK |
SPI (SCLK) |
| D6 |
GPIO12 |
OK |
OK |
SPI (MISO) |
| D7 |
GPIO13 |
OK |
OK |
SPI (MOSI) |
| D8 |
GPIO15 |
pulled to GND |
OK |
SPI (CS) - Boot fails if pulled HIGH |
| RX |
GPIO3 |
OK |
RX pin |
HIGH at boot |
| TX |
GPIO1 |
TX pin |
OK |
HIGH at boot - debug output at boot, boot fails if pulled LOW |
| A0 |
ADC0 |
Analog Input |
--- |
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