fixed error, updated defaults, added notes

Travis fix - only allow ultralcd_st7920_u8glib_rrd_AVR.cpp to compile when ST7920 selected

Marlin/src/lcd/dogm/HAL_LCD_class_defines.h

 };
 
 
-
+// AVR version uses ultralcd_st7920_u8glib_rrd_AVR.cpp, HAL version uses u8g_dev_st7920_128x64_HAL.cpp
 extern u8g_dev_t u8g_dev_st7920_128x64_rrd_sw_spi;
 class U8GLIB_ST7920_128X64_RRD : public U8GLIB
 {

Marlin/src/lcd/dogm/ultralcd_st7920_u8glib_rrd_AVR.cpp

 
 #include "../../inc/MarlinConfig.h"
 
-#if ENABLED(DOGLCD)
+#if ENABLED(U8GLIB_ST7920)
 
 #ifndef U8G_HAL_LINKS
 
-//#include "../../Marlin.h"
-
-//#if ENABLED(U8GLIB_ST7920)
-//#if ( ENABLED(SHARED_SPI) || !ENABLED(SHARED_SPI) && (defined(LCD_PINS_D4) &&  LCD_PINS_D4 >= 0) &&  (defined(LCD_PINS_ENABLE) &&  LCD_PINS_ENABLE >= 0))
-
-#define ST7920_CLK_PIN  23
-#define ST7920_DAT_PIN  17
-#define ST7920_CS_PIN   16
-
-/*
 #define ST7920_CLK_PIN  LCD_PINS_D4
 #define ST7920_DAT_PIN  LCD_PINS_ENABLE
 #define ST7920_CS_PIN   LCD_PINS_RS
-*/
 
 //#define PAGE_HEIGHT 8   //128 byte framebuffer
 #define PAGE_HEIGHT 16  //256 byte framebuffer
 
 #pragma GCC reset_options
 
-//#endif //( ENABLED(SHARED_SPI) || !ENABLED(SHARED_SPI) && (defined(LCD_PINS_D4) &&  LCD_PINS_D4 >= 0) &&  (defined(LCD_PINS_ENABLE) &&  LCD_PINS_ENABLE >= 0))
-//#endif // U8GLIB_ST7920
-
 #endif // U8G_HAL_LINKS
 
-#endif // DOGLCD
+#endif // U8GLIB_ST7920

Marlin/src/lcd/ultralcd_impl_DOGM.h

 
 // LCD selection
 #if ENABLED(REPRAPWORLD_GRAPHICAL_LCD)
-  #ifdef CPU_32_BIT // SPI too fast with 32bit?
+  #ifdef CPU_32_BIT 
     U8GLIB_ST7920_128X64_4X u8g(LCD_PINS_D4, LCD_PINS_ENABLE, LCD_PINS_RS); // Original u8glib device. 2 stripes, SW SPI
   #else
-    U8GLIB_ST7920_128X64_4X u8g(LCD_PINS_RS); // 2 stripes, HW SPI
+    U8GLIB_ST7920_128X64_4X u8g(LCD_PINS_RS); // 2 stripes, HW SPI (shared with SD card)
   #endif
 #elif ENABLED(U8GLIB_ST7920)
   // RepRap Discount Full Graphics Smart Controller
-    //U8GLIB_ST7920_128X64_4X u8g(LCD_PINS_RS); // 2 stripes, HW SPI
+    //U8GLIB_ST7920_128X64_4X u8g(LCD_PINS_RS); // 2 stripes, HW SPI (shared with SD card, on AVR does not use standard LCD adapter)
     //U8GLIB_ST7920_128X64_4X u8g(LCD_PINS_D4, LCD_PINS_ENABLE, LCD_PINS_RS); // Original u8glib device. 2 stripes, SW SPI
     U8GLIB_ST7920_128X64_RRD u8g(LCD_PINS_D4, LCD_PINS_ENABLE, LCD_PINS_RS); // Number of stripes can be adjusted in ultralcd_st7920_u8glib_rrd.h with PAGE_HEIGHT
                                                                            // AVR version ignores these pin settings
 
 #elif ENABLED(U8GLIB_SSD1306)
   // Generic support for SSD1306 OLED I2C LCDs
-    //U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST);  // 8 stripes
+    //U8GLIB_SSD1306_128X64_2X_I2C_2_WIRE  u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST); // 4 stripes
-    U8GLIB_SSD1306_128X64_2X_I2C_2_WIRE  u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST); // 4 stripes
+    U8GLIB_SSD1306_128X64_2X u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST); // 4 stripes
-    //U8GLIB_SSD1306_128X64_2X u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST); // 4 stripes
 
 #elif ENABLED(MKS_12864OLED)
   // MKS 128x64 (SH1106) OLED I2C LCD
     //U8GLIB_SH1106_128X64_2X u8g(DOGLCD_SCK, DOGLCD_MOSI, DOGLCD_CS, DOGLCD_A0); // 4 stripes
 #elif ENABLED(U8GLIB_SH1106)
   // Generic support for SH1106 OLED I2C LCDs
-    //U8GLIB_SH1106_128X64 u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST);  // 8 stripes
+    //U8GLIB_SH1106_128X64_2X_I2C_2_WIRE  u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST); // 4 stripes
-    U8GLIB_SH1106_128X64_2X_I2C_2_WIRE  u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST); // 4 stripes
+    U8GLIB_SH1106_128X64_2X u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST); // 4 stripes
-    //U8GLIB_SH1106_128X64_2X u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_FAST); // 4 stripes
 #elif ENABLED(MINIPANEL)
   // The MINIPanel display
     //U8GLIB_MINI12864 u8g(DOGLCD_CS, DOGLCD_A0);  // 8 stripes