ESP-01 Wi-Fi Module
Minimal ESP8266 breakout for adding Wi-Fi to any microcontroller.
A bare-bones ESP8266 Wi-Fi module controllable via AT commands, a cheap way to bolt Wi-Fi connectivity onto non-networked microcontrollers. The ESP-01 exposes just enough pins — power, UART, and two GPIO — to run the module in its simplest mode: forward AT commands over serial from an existing microcontroller like an Arduino Uno, and let the ESP-01 handle all the Wi-Fi networking, making it a low-cost bridge for otherwise offline projects that just need occasional connectivity (sending sensor data to the cloud, receiving simple remote commands).
Specifications
| Wi-Fi chipset | ESP8266 SoC, 802.11 b/g/n 2.4GHz Wi-Fi |
| Operating voltage | 3.3V DC only (NOT 5V tolerant on any pin) |
| Operating current | ~80 mA average, spikes to 200-300 mA during Wi-Fi transmit bursts |
| Flash memory | Typically 1MB onboard SPI flash on standard ESP-01 boards (ESP-01S variants may have more) |
| GPIO | Only 2 usable GPIO pins broken out (GPIO0, GPIO2) — the most limiting factor of this module |
| Programming interface | UART (TX/RX), controlled via AT command firmware by default, or reflashed with custom Arduino-core firmware |
| Form factor | Very small 8-pin module, the smallest and cheapest of the common ESP8266 breakout family |
Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | VCC | Power, 3.3V DC only — do not supply 5V |
| 2 | GND | Ground |
| 3 | TX | UART transmit — connect to microcontroller RX |
| 4 | RX | UART receive — connect to microcontroller TX (3.3V logic, level-shift from 5V boards) |
| 5 | GPIO0 | General I/O; must be pulled LOW at boot to enter flashing mode, HIGH for normal AT-command run mode |
| 6 | GPIO2 | General I/O; must be pulled HIGH at boot for normal operation |
| 7 | CH_PD / EN | Chip enable — must be pulled HIGH for the module to run |
| 8 | RST | Active-LOW reset pin |
All ESP-01 pins are strictly 3.3V — connecting directly to a 5V Arduino's logic pins without a level shifter or resistor divider will damage the chip. The module also draws current spikes during Wi-Fi transmission that a microcontroller's onboard 3.3V regulator often can't supply reliably, so a separate 3.3V regulator capable of a few hundred mA is strongly recommended rather than powering it from an Arduino's 3.3V pin.
Variants
Use the ESP-01 only when the goal is a minimal Wi-Fi bridge for an existing microcontroller that just needs to send/receive occasional data. If the project could instead run entirely on the ESP8266 itself (skipping a separate Arduino), an ESP-12E-based module or NodeMCU dev board is far more capable for barely more cost.
| Variant | Temp range | Hum range | Accuracy | Protocol | Price |
|---|---|---|---|---|---|
| ESP-01 (1MB flash, AT command firmware) | ~$1-2 | ||||
| ESP-01S | ~$1-3 | ||||
| ESP-12E / ESP-12F (or NodeMCU dev board) | ~$2-6 |