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ESP-01S ESP8266 3.3V WiFi Serial Module Wireless Transceiver for Arduino Projects
ESP-01S ESP8266 3.3V WiFi Serial Module Wireless Transceiver for Arduino Projects
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ESP-01S ESP8266 3.3V WiFi Serial Module — Wireless Transceiver for Arduino & IoT Projects
The ESP-01S is a compact WiFi serial transceiver module based on the Espressif ESP8266 SoC, providing 802.11 b/g/n WiFi connectivity via a simple UART AT command interface or direct SDK programming. The ESP-01S variant includes 1MB of flash memory (vs 512KB on the original ESP-01), enabling larger firmware images and OTA (over-the-air) update capability. Widely used for adding WiFi connectivity to Arduino, STM32, and other microcontroller projects, or as a standalone IoT node programmed directly with the ESP8266 Arduino core or Espressif SDK.
Technical Specifications
| Parameter | Value |
|---|---|
| SoC | Espressif ESP8266EX |
| Flash Memory | 1MB (ESP-01S) / 512KB (ESP-01) |
| WiFi Standard | 802.11 b/g/n, 2.4GHz |
| WiFi Modes | Station (STA), Access Point (AP), STA+AP |
| Security | WEP, WPA, WPA2 (Personal) |
| Interface | UART (TX, RX, 115200 baud default) |
| GPIO Pins | GPIO0, GPIO2 (2 usable GPIO) |
| Supply Voltage | 3.3V DC (do NOT connect to 5V directly) |
| Peak Current | ~300mA (during WiFi transmission) |
| Antenna | PCB trace antenna (onboard) |
| Programming | AT commands (via UART) or ESP8266 Arduino core / SDK |
| Certification | CE, RoHS |
AT Command Reference (Key Commands)
| Command | Function |
|---|---|
| AT | Test (returns OK) |
| AT+CWMODE=1 | Set Station mode |
| AT+CWJAP="SSID","PWD" | Connect to WiFi network |
| AT+CIFSR | Get IP address |
| AT+CIPSTART | Open TCP/UDP connection |
| AT+CIPSEND | Send data |
| AT+CIPSERVER | Start TCP server |
Typical Applications
- Arduino WiFi Shield: Add WiFi connectivity to Arduino Uno/Mega via UART AT commands — send sensor data to ThingSpeak, Blynk, or MQTT broker over WiFi
- Standalone IoT Node: Program the ESP-01S directly with the ESP8266 Arduino core to create a self-contained WiFi sensor node (temperature, humidity, motion) without an external MCU
- Smart Home Automation: WiFi relay controller, smart switch, or sensor node for Home Assistant, OpenHAB, or custom MQTT-based home automation systems
- OTA Firmware Updates: The 1MB flash of the ESP-01S enables OTA firmware updates via WiFi, allowing remote firmware deployment without physical access to the device
- Web Server: Host a simple HTTP web server on the ESP-01S to provide a browser-based control interface for IoT devices on the local network
- WiFi-to-Serial Bridge: Use the ESP-01S as a transparent WiFi-to-UART bridge for wireless serial communication between a PC and a microcontroller
Arduino Wiring (AT Command Mode)
- ESP-01S VCC → 3.3V (use AMS1117-3.3 regulator from 5V — do NOT use Arduino 3.3V pin directly, insufficient current)
- ESP-01S GND → GND | CH_PD → 3.3V (enable pin, must be HIGH)
- ESP-01S TX → Arduino D2 (SoftwareSerial RX) | RX → D3 via 1kΩ/2kΩ voltage divider
- Use
SoftwareSerial esp(2, 3);andesp.begin(115200);
FAQ
Q: Can I power the ESP-01S from the Arduino 3.3V pin?
A: Not recommended. The Arduino 3.3V pin provides only 50–150mA, while the ESP8266 draws up to 300mA during WiFi transmission. Use a dedicated AMS1117-3.3 or LM1117-3.3 regulator from the 5V rail for reliable operation.
Q: What is the difference between ESP-01 and ESP-01S?
A: The ESP-01S has 1MB flash (vs 512KB on ESP-01), a blue LED on GPIO2 (vs red LED on GPIO0 on ESP-01), and the CH_PD pin is pulled high internally. The ESP-01S is the recommended variant for new designs.
Package Contents
- 1 × ESP-01S ESP8266 WiFi serial module
