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Add WiFi to Any Microcontroller via Serial — Tiny, Low-Cost, Proven
The ESP-01S 1MB WiFi Serial Transceiver Module is the simplest way to add WiFi connectivity to an Arduino, STM32, PIC, or any microcontroller with a UART port. Send AT commands over serial and the ESP-01S handles all WiFi networking — TCP connections, HTTP requests, UDP, and more — without consuming your main MCU's resources.
The "S" variant upgrades the original ESP-01 with 1 MB of flash (double the original 512 KB), a cleaner PCB layout, and a dark blue PCB that reduces light interference on the onboard LED — making it better for production use.
ESP-01 (512 KB) vs ESP-01S (1 MB) — which should you buy?
| Feature | ESP-01S (this product) | ESP-01 (512 KB) |
|---|---|---|
| Flash memory | 1 MB — room for MicroPython, custom firmware | 512 KB — AT firmware only |
| PCB color | Dark blue — reduced LED bleed | Light blue |
| GPIO pins | 2 (GPIO0, GPIO2) | 2 (GPIO0, GPIO2) |
| Standalone capable | ✅ Yes — can run full firmware | Limited — AT firmware fits tightly |
| Recommended for | New designs — more headroom for firmware | Budget AT-command-only applications |
Key features
- AT command interface: Control WiFi over UART — no extra library needed on host MCU
- 1 MB flash: Supports MicroPython, NodeMCU Lua, and custom firmware
- Station + AP modes: Connect to a network or create its own hotspot
- Integrated TCP/IP stack: HTTP, UDP, TCP handled onboard
- 2 GPIO pins: Useful for simple sensor reads or LED control alongside WiFi duties
- Ultra-compact: 14.3 × 24.8 mm — fits nearly anywhere
Technical specifications
| Model | ESP-01S |
|---|---|
| Core Chip | ESP8266EX |
| Flash Memory | 1 MB SPI Flash |
| GPIO Pins | 2 (GPIO0, GPIO2) |
| WiFi Standard | 802.11 b/g/n, 2.4 GHz |
| Interface | UART (AT commands), 115200 baud default |
| Operating Voltage | 3.0V – 3.6V |
| Operating Current | ~80 mA average |
| Dimensions | 14.3 × 24.8 mm |
| Antenna | PCB trace antenna |
Frequently Asked Questions
Can I use this with a 5V Arduino? The ESP-01S runs on 3.3V. You need a 3.3V power supply and a logic level shifter (or voltage divider) on the TX pin from Arduino to ESP. The ESP TX → Arduino RX is fine at 3.3V.
Can I program it directly without a host MCU? Yes. With 1 MB flash, you can run MicroPython or custom Arduino firmware standalone by pulling GPIO0 LOW during reset to enter flash mode.
What is the baud rate for AT commands? Default is 115200 baud on most firmware versions.
Manila stock. Order before 16:00 PHT, ships today via J&T or LBC. Provincial: 1–3 working days.
Schools / class POs: we accept Purchase Orders for accredited schools and universities. contact us with your PO details.
Returns: 7-day inspection window for DOA units. Email proof of issue and we ship a replacement.
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