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libraries/GxEPD2/extras/sw_spi/README.MD

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+### support for SW SPI for GxEPD2
+
+GxEPD2 supports only HW SPI with the unmodified library.
+The replacement files in the src directory provide the option to use SW SPI.
+This is a workaround and not very elegant, therefore it is provided as a replacement only.
+
+To use SW SPI with GxEPD2:
+- copy the files GxEPD2_EPD.h and GxEPD2_EPD.cpp from the subdirectoy .src to the .src directory of the library.
+- add the special call to the added init method BEFORE the normal init method:
+  display.epd2.init(SW_SCK, SW_MOSI, 115200, true, 20, false); // define or replace SW_SCK, SW_MOSI
+  display.init(115200); // needed to init upper level
+  
+To use the modified library with HW SPI
+  - comment out the special init call:
+  //display.epd2.init(SW_SCK, SW_MOSI, 115200, true, 20, false); // define or replace SW_SCK, SW_MOSI
+  display.init(115200);
+
+To switch back to using HW SPI during run time
+  display.epd2.init(-1, -1, 115200, true, 20, false); // revert to HW SPI
+  display.init(115200); // needed to init upper level
+
+The SW SPI allows also to read through MOSI pin from DIN of e-paper controller
+  data = display.epd2._readData();
+  display.epd2._readData(data, n);