This speeds up the ESP8266WebServer::streamFile more than 3 times. Tested on streaming the 800+ Kb file from SD (FAT32), average time without a fix was 9000 ms, with the fix is 2600 ms (maximal possible SPI speed used), which is as fast as streaming the same file from internal SPIFFS. Hardware: WeMos D1 mini.
SD Library for Arduino
The SD library allows for reading from and writing to SD cards.
For more information about this library please visit us at http://www.arduino.cc/en/Reference/SD
License
Copyright (C) 2009 by William Greiman Copyright (c) 2010 SparkFun Electronics
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.