Keyboard class is almost done

src/Keyboard.cpp

@@ -0,0 +1,103 @@
+#include "Keyboard.h"
+//#define DEBUG
+#define PIN_WIRE_SDA D3
+#define PIN_WIRE_SCL D4
+Keyboard::Keyboard(uint8_t debounce)
+{
+    this->debounce = debounce;
+}
+void Keyboard::begin(TwoWire *databus)
+{
+    pcf8574 = new PCF8574(databus, 0x27, PIN_WIRE_SDA, PIN_WIRE_SCL);
+    pcf8574->pinMode(0, OUTPUT);
+    for (int i = 1; i < 8; i++)
+    {
+        if (i < 5)
+            pcf8574->pinMode(i, INPUT_PULLUP);
+        else
+            pcf8574->pinMode(i, OUTPUT);
+    }
+
+    Serial.print("Init pcf8574...");
+    if (pcf8574->begin())
+        Serial.println("OK");
+    else
+        Serial.println("KO");
+
+    pcf8574->digitalWrite(1, HIGH);
+    for (int i = 5; i < 8; i++)
+        pcf8574->digitalWrite(i, HIGH);
+}
+Keyboard::~Keyboard()
+{
+    if (pcf8574 != nullptr)
+        delete pcf8574;
+}
+void Keyboard::scan()
+{
+    if (millis() < timeElapsed + this->debounce)
+        return 0;
+    uint8_t key = 0;
+    for (int i = 7; i > 4; i--) // Columns
+    {
+        pcf8574->digitalWrite(i, LOW);
+        for (int j = 1; j < 5; j++)
+        { // Rows
+            key++;
+            uint8_t val = pcf8574->digitalRead(j);
+#ifdef DEBUG
+            Serial.println("i=" + String(i) + " j=" + String(j) + " v=" + String(val));
+            delay(500);
+#endif
+            if (val == 0)
+            {
+                timeElapsed = millis();
+                this->lastKey = key;
+                this->buffer.push(mapChr(key));
+            }
+        }
+        pcf8574->digitalWrite(i, HIGH);
+    }
+}
+char Keyboard::mapChr(uint8_t key)
+{
+
+    switch (key)
+    {
+    case 1:
+        return '1';
+    case 2:
+        return '4';
+    case 3:
+        return '7';
+    case 4:
+        return 'O';
+    case 5:
+        return '5';
+    case 6:
+        return '1';
+    case 7:
+        return '8';
+    case 8:
+        return '0';
+    case 9:
+        return '3';
+    case 10:
+        return '6';
+    case 11:
+        return '9';
+    case 12:
+        return 'X';
+
+    default:
+        return 'F';
+    }
+}
+char Keyboard::getChr()
+{
+    return this->getChr(this->lastKey);
+}
+
+bool Keyboard::available(){
+    return (!this->buffer.empty());
+}

src/Keyboard.h

@@ -0,0 +1,23 @@
+#ifndef KEYBOARD_CLASS
+#define KEYBOARD_CLASS
+#include "PCF8574.h"
+#include <bits/stdc++.h> 
+class Keyboard
+{
+private:
+    unsigned long timeElapsed;
+    std::queue<char> buffer;
+    uint8_t debounce;
+    PCF8574* pcf8574;
+    int lastKey;
+    /* data */
+public:
+    Keyboard(uint8_t debounce);
+    ~Keyboard();
+    void scan();
+    void begin(TwoWire *databus);
+    static char getChr(uint8_t key);
+    char getChr();
+    bool available();
+};
+#endif

src/main.cpp

@@ -0,0 +1,26 @@
+
+#include <Arduino.h>
+#include <Wire.h>
+#include "Keyboard.h"
+
+#define PIN_WIRE_SDA D3
+#define PIN_WIRE_SCL D4
+#include <LiquidCrystal_I2C.h>
+TwoWire databus;
+Keyboard keyboard(200);
+void setup()
+{
+	Serial.begin(9600);
+	Serial.print("Starting");
+	delay(500);
+	keyboard.begin(&databus);
+}
+
+
+
+void loop()
+{
+	char key = keyboard.getKey();
+	if(key!=0)
+		Serial.println("Key " + String(key) +  "was pressed");
+}