add back pull-down support

Author: Links2004

hardware/esp8266com/esp8266/cores/esp8266/core_esp8266_wiring_digital.c

@@ -59,13 +59,17 @@ extern void __pinMode(uint8_t pin, uint8_t mode) {
       GPF(pin) = GPFFS(GPFFS_GPIO(pin));//Set mode to GPIO
       GPC(pin) = (GPC(pin) & (0xF << GPCI)); //SOURCE(GPIO) | DRIVER(NORMAL) | INT_TYPE(UNCHANGED) | WAKEUP_ENABLE(DISABLED)
       GPES = (1 << pin); //Enable
-    } else if(mode == INPUT || mode == INPUT_PULLUP){
+    } else if(mode == INPUT || mode == INPUT_PULLUP || mode == INPUT_PULLDOWN){
       GPF(pin) = GPFFS(GPFFS_GPIO(pin));//Set mode to GPIO
       GPC(pin) = (GPC(pin) & (0xF << GPCI)) | (1 << GPCD); //SOURCE(GPIO) | DRIVER(OPEN_DRAIN) | INT_TYPE(UNCHANGED) | WAKEUP_ENABLE(DISABLED)
       GPEC = (1 << pin); //Disable
-      if(mode == INPUT_PULLUP){
-        GPF(pin) |= (1 << GPFPU);//Enable Pullup
-      }
+        if(mode == INPUT_PULLUP) {
+            GPF(pin) &= ~(1 << GPFPD); // Disable Pulldown
+            GPF(pin) |= (1 << GPFPU);  // Enable  Pullup
+        } else if(mode == INPUT_PULLDOWN) {
+            GPF(pin) &= ~(1 << GPFPU); // Disable Pullup
+            GPF(pin) |= (1 << GPFPD);  // Enable  Pulldown
+        }
     }
   } else if(pin == 16){
     GPF16 = GP16FFS(GPFFS_GPIO(pin));//Set mode to GPIO

hardware/esp8266com/esp8266/cores/esp8266/esp8266_peri.h

@@ -93,9 +93,11 @@ static uint8_t esp8266_gpioToFn[16] = {0x34, 0x18, 0x38, 0x14, 0x3C, 0x40, 0x1C,
 //GPIO (0-15) PIN Function Bits
 #define GPFSOE 0 //Sleep OE
 #define GPFSS  1 //Sleep Sel
+#define GPFSPD 2 //Sleep Pulldown
 #define GPFSPU 3 //Sleep Pullup
 #define GPFFS0 4 //Function Select bit 0
 #define GPFFS1 5 //Function Select bit 1
+#define GPFPD  6 //Pulldown
 #define GPFPU  7 //Pullup
 #define GPFFS2 8 //Function Select bit 2
 #define GPFFS(f) (((((f) & 4) != 0) << GPFFS2) | ((((f) & 2) != 0) << GPFFS1) | ((((f) & 1) != 0) << GPFFS0))