Esp8266 Esp-01 Datasheet May 2026

If you’ve ever dabbled in IoT or low-cost WiFi-enabled projects, you’ve almost certainly encountered the ESP8266 ESP-01 . It’s the little module that started a revolution. But before you plug it into a breadboard and fry it, let’s take a detailed walk through its official datasheet and extract everything that matters for your projects. 1. What Exactly is the ESP-01? The ESP-01 is a breakout board for the ESP8266EX chip. It’s not the chip itself, but a minimal module designed to make the chip usable for hobbyists.

┌─────────┐ TX │1 8│ VCC (3.3V) RX │2 7│ RST CH_PD │3 6│ GPIO0 GPIO2 │4 5│ GPIO1 (TX onboard LED) └─────────┘ esp8266 esp-01 datasheet

| Pin | Name | Function | Important Notes | |-----|------|----------|------------------| | 1 | TX | Serial TX (UART0) | 3.3V logic | | 2 | RX | Serial RX (UART0) | 3.3V logic – | | 3 | CH_PD | Chip enable | Pull HIGH (3.3V) to turn on | | 4 | GPIO2 | General purpose I/O | Internal pull-up, must be HIGH at boot | | 5 | GPIO1 | General purpose I/O | Also UART TXD | | 6 | GPIO0 | General purpose I/O | Boot mode selection (see below) | | 7 | RST | Reset | Active LOW | | 8 | VCC | 3.3V input | Max 3.6V absolute | 3. Boot Modes – The Most Confusing Part The datasheet explicitly lists boot configuration pins . If these are wrong, your module won’t boot or won’t accept new firmware. If you’ve ever dabbled in IoT or low-cost

| Mode | GPIO0 | GPIO2 | GPIO1 (TX) | |------|-------|-------|-------------| | | 0 | 1 | 1 | | Flash Boot (Normal Run) | 1 | 1 | 1 | | SDIO Boot | 0 | 1 | 0 | It’s not the chip itself, but a minimal