WiFi Serial TTL Module ESP-01 – ESP8266

ESP-01 (old version), ESP-01S (updated version).

specification:
SDIO 2.0, SPI, UART
Four pins interface, VCC-3V3, GND, TXD and RXD. Two extra GPIOs can use.
AT commands firmware. New IC ESP8266ex
Wi-Fi Direct (P2P), soft-AP
Integrated TCP/IP protocol stack
Integrated TR switch, balun, LNA, power amplifier and matching network
Integrated PLLs, regulators, DCXO and power management units
+19.5dBm output power in 802.11b mode
Power down leakage current of <10uA
Integrated low power 32-bit CPU could be used as application processor
SDIO 1.1/2.0, SPI, UART
STBC, 1×1 MIMO, 2×1 MIMO
A-MPDU & A-MSDU aggregation & 0.4ms guard interval
Integrated RF switch, balun, 24dBm PA, DCXO, and PMU
Integrated RISC processor, on-chip memory and external memory interfaces
Integrated MAC/baseband processors
Quality of Service management
I2S interface for high fidelity audio applications
On-chip low-dropout linear regulators for all internal supplies
Proprietary spurious-free clock generation architecture
Integrated WEP, TKIP, AES, and WAPI engines
Serial/UART baud rate: 115200 bps
Input power: 3.3V
I/O voltage tolerance: 3.6V Max
Flash Memory Size: 1MB (8Mbit)
WiFi security modes: WPA, WPA2