AI Thinker is now offering ESP-14 WiFi module that combines ESP8266 and STM8S 8 bit MCUs.
ESP-14 measures 24 x 16 mm and consumes mere 70 mA under standby mode. ESP-14 WiFi module specifications include
WiSoC – Expressif ESP8266-EX WiSoC; MCU – STMicro STM8S003F3P6 8-bit MCU @ 16 MHz with 1KB RAM, 8KB flash, and 128 bytes EEPROM; Connectivity – 802.11 b/g/n WiFi I/Os; STM8: 15 GPIOs also supporting I2C, SPI, UART, and up to 5 10-bit ADC; ESP8266: E_GPIO0 to select operating mode (running or download) and Power Supply – 3.3V
Shown below is the diagram of their pinouts.
ESP8266 is controlled by STM8S by AT commands and all but one of the input-outputs are directly connected to the STM8S. There are two advantages of it – 5 ADC inputs are available and when you are not using wireless LAN, you will be able to turn off ESP8266 completely.