add SPIClass::transfer16 (needed by some display libs)

Author: Links2004

hardware/esp8266com/esp8266/libraries/SPI/SPI.cpp

@@ -57,7 +57,7 @@ void SPIClass::setDataMode(uint8_t dataMode) {
 }
 
 void SPIClass::setBitOrder(uint8_t bitOrder) {
-  if (bitOrder == MSBFIRST){
+  if (bitOrder == MSBFIRST) {
     SPI1C &= ~(SPICWBO | SPICRBO);
   } else {
     SPI1C |= (SPICWBO | SPICRBO);
@@ -76,3 +76,25 @@ uint8_t SPIClass::transfer(uint8_t data) {
   return (uint8_t)(SPI1W0 & 0xff);
 }
 
+uint16_t SPIClass::transfer16(uint16_t data) {
+    union {
+            uint16_t val;
+            struct {
+                    uint8_t lsb;
+                    uint8_t msb;
+            };
+    } in, out;
+    in.val = data;
+
+    if((SPI1C & (SPICWBO | SPICRBO))) {
+        //MSBFIRST
+        out.msb = transfer(in.msb);
+        out.lsb = transfer(in.lsb);
+    } else {
+        //LSBFIRST
+        out.lsb = transfer(in.lsb);
+        out.msb = transfer(in.msb);
+    }
+    return out.val;
+}
+

hardware/esp8266com/esp8266/libraries/SPI/SPI.h

@@ -80,6 +80,7 @@ class SPIClass {
   void setClockDivider(uint32_t clockDiv);
   void beginTransaction(SPISettings settings);
   uint8_t transfer(uint8_t data);
+  uint16_t transfer16(uint16_t data);
   void endTransaction(void);
 };