Some wemos examples from

http://nopnop2002.webcrow.jp

examples/interruptWemos/interruptWemos.ino

@@ -0,0 +1,68 @@
+/*
+ * PCF8574 GPIO Port Expand
+ * http://nopnop2002.webcrow.jp/WeMos/WeMos-25.html
+ *
+ * PCF8574    ----- WeMos
+ * A0         ----- GRD
+ * A1         ----- GRD
+ * A2         ----- GRD
+ * VSS        ----- GRD
+ * VDD        ----- 5V/3.3V
+ * SDA        ----- GPIO_4
+ * SCL        ----- GPIO_5
+ * INT        ----- GPIO_13
+ *
+ * P0     ----------------- BUTTON0
+ * P1     ----------------- BUTTON1
+ * P2     ----------------- BUTTON2
+ * P3     ----------------- BUTTON3
+ * P4     ----------------- BUTTON4
+ * P5     ----------------- BUTTON5
+ * P6     ----------------- BUTTON6
+ * P7     ----------------- BUTTON7
+ *
+ */
+
+#include "Arduino.h"
+#include "PCF8574.h"  // https://github.com/xreef/PCF8574_library
+
+#define ESP8266_INTERRUPTED_PIN 13
+
+// Set i2c address
+PCF8574 pcf8574(0x20);
+
+// Function interrupt
+bool keyPressed = false;
+
+void keyPressedOnPCF8574(){
+//  Serial.println("keyPressedOnPCF8574");
+  keyPressed = true;
+}
+
+void setup()
+{
+  Serial.begin(9600);
+  pinMode(ESP8266_INTERRUPTED_PIN, INPUT_PULLUP);
+  attachInterrupt(digitalPinToInterrupt(ESP8266_INTERRUPTED_PIN), keyPressedOnPCF8574, FALLING);
+
+  for(int i=0;i<8;i++) {
+    pcf8574.pinMode(i, INPUT);
+  }
+  pcf8574.begin();
+}
+
+void loop()
+{
+  if (keyPressed){
+    PCF8574::DigitalInput val = pcf8574.digitalReadAll();
+    if (val.p0==HIGH) Serial.println("KEY0 PRESSED");
+    if (val.p1==HIGH) Serial.println("KEY1 PRESSED");
+    if (val.p2==HIGH) Serial.println("KEY2 PRESSED");
+    if (val.p3==HIGH) Serial.println("KEY3 PRESSED");
+    if (val.p4==HIGH) Serial.println("KEY4 PRESSED");
+    if (val.p5==HIGH) Serial.println("KEY5 PRESSED");
+    if (val.p6==HIGH) Serial.println("KEY6 PRESSED");
+    if (val.p7==HIGH) Serial.println("KEY7 PRESSED");
+    keyPressed= false;
+  }
+}