Update notes in response to #1475

On ESP8266 when using overlap, only one SPI device can share the FLASH SPI bus .

README.md

@@ -91,7 +91,7 @@ The Button class from Adafruit_GFX is incorporated, with the enhancement that th
 
 # ESP8266 overlap mode
 
-The library supports SPI overlap on the ESP8266 so the TFT screen can share MOSI, MISO and SCLK pins with the program FLASH, this frees up GPIO pins for other uses.
+The library supports SPI overlap on the ESP8266 so the TFT screen can share MOSI, MISO and SCLK pins with the program FLASH, this frees up GPIO pins for other uses. Only one SPI device can be connected to the FLASH pins and the chips select for the TFT must be on pin D3 (GPIO0).
 
 
 # Fonts

User_Setup.h

@@ -175,6 +175,8 @@
 // Overlap mode shares the ESP8266 FLASH SPI bus with the TFT so has a performance impact
 // but saves pins for other functions. It is best not to connect MISO as some displays
 // do not tristate that line when chip select is high!
+// Note: Only one SPI device can share the FLASH SPI lines, so a SPI touch controller
+// cannot be connected as well to the same SPI signals.
 // On NodeMCU 1.0 SD0=MISO, SD1=MOSI, CLK=SCLK to connect to TFT in overlap mode
 // On NodeMCU V3  S0 =MISO, S1 =MOSI, S2 =SCLK
 // In ESP8266 overlap mode the following must be defined

User_Setups/Setup9_ST7735_Overlap.h

@@ -17,7 +17,9 @@
 
 // Overlap mode shares the ESP8266 FLASH SPI bus with the TFT so has a performance impact
 // but saves pins for other functions. It is best not to connect MISO as some displays
-// do not tristate that line wjen chip select is high!
+// do not tristate that line when chip select is high!
+// Note: Only one SPI device can share the FLASH SPI lines, so a SPI touch controller
+// cannot be connected as well to the same SPI signals.
 // On NodeMCU 1.0 SD0=MISO, SD1=MOSI, CLK=SCLK to connect to TFT in overlap mode
 // On NodeMCU V3  S0 =MISO, S1 =MOSI, S2 =SCLK
 // In ESP8266 overlap mode the following must be defined