Based on ESP8266 Wifi IC, a new version of ESP-12S.
Add extra I/Os and SPI pin interfaces: MTDO, MTDI, SD_3, MTMS, MTCK, SD_2 (GPIO10, GPIO9, CLK, CS, DI, DO)
The rest foot price and size remains same with ESP-12.
Improved the capability of anti-EMI
ESP_12S PCB file:
ESP_12S PCB file