//GPA start 0x00
//GPB start 0x01
//command input 0xFF
//command output 0x00

//when u start transaction  
  //call GPA is 0x12
  //put high and low with 0 or 1 in 8 bit
  //call GPA is 0x13
  //put high and low with 0 or 1 in 8 bit
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32
#define MCP23017 0x27

Adafruit_SSD1306 display(SCREEN_WIDTH,SCREEN_HEIGHT, &Wire);

bool stateISR = true;
unsigned long period = 1000;
unsigned long last_time = 0;

void setup() {
  Serial.begin(115200);
  Wire.begin(); 


  //Open Port A
  Wire.beginTransmission(MCP23017); 
  Wire.write(0x00); //address  GPA
  Wire.write(0x00); //output 0xFF is input  
  Wire.endTransmission();

  //Open Port B
  Wire.beginTransmission(MCP23017); 
  Wire.write(0x01);  //address GPB
  Wire.write(0x00); //output 0xFF is input
  Wire.endTransmission();

  //DISPLAY 
   if(!display.begin(SSD1306_SWITCHCAPVCC,0x3C))
  {
    Serial.println(F("SSD1306 allocation failed"));
  }
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.println(F("ESP32 I2C MCP23017"));
  display.display();
}


void show_led8()
{
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.println(F("ESP32 I2C MCP23017"));
  display.setCursor(0,16);
  display.println(F("LED8 = ON || LED9 = OFF"));
  display.display();
}
void show_led9()
{
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.println(F("ESP32 I2C MCP23017"));
  display.setCursor(0,16);
  display.println(F("LED8 = OFF || LED9 = ON"));
  display.display();
}
void led8_on()
{
  Wire.beginTransmission(MCP23017); 
  Wire.write(0x12); //address  GPA
  Wire.write(0x80); 
  Wire.endTransmission();
}
void led8_off()
{
  Wire.beginTransmission(MCP23017); 
  Wire.write(0x12); //address  GPA
  Wire.write(0x00); 
  Wire.endTransmission();
}

void led9_on()
{
  Wire.beginTransmission(MCP23017); 
  Wire.write(0x13); //address  GPB
  Wire.write(0x01); //out port0
  Wire.endTransmission();
}

void led9_off()
{
  Wire.beginTransmission(MCP23017); 
  Wire.write(0x13); //address  GPB
  Wire.write(0x00); //out port0
  Wire.endTransmission();
}
void loop() {
  if(millis() - last_time >= period)
  {
    last_time = millis();
    if(stateISR)
    {
      led8_on();
      led9_off();
      show_led8();
    }
    else
    {
      led9_on();
      led8_off();
      show_led9();
    }
    stateISR = !stateISR;
  }
}