ESP8266 SD Card SPI Mode
TBC source
http://www.pratikpanda.com/esp8266-sd-card-interfacing-part-1/
http://www.pratikpanda.com/esp8266-sd-card-interfacing-part-2/
TBC source
http://www.pratikpanda.com/esp8266-sd-card-interfacing-part-1/
http://www.pratikpanda.com/esp8266-sd-card-interfacing-part-2/