/*
    Description: SIM800L serial transparent transmission debugging program
*/
#include <M5Stack.h>
#define RX_PIN      16
#define TX_PIN      17
#define RESET_PIN   5   

void header(const char *string, uint16_t color){
    M5.Lcd.fillScreen(color);
    M5.Lcd.setTextSize(1);
    M5.Lcd.setTextColor(TFT_MAGENTA, TFT_BLUE);
    M5.Lcd.fillRect(0, 0, 320, 30, TFT_BLUE);
    M5.Lcd.setTextDatum(TC_DATUM);
    M5.Lcd.drawString(string, 160, 3, 4);
}

void setup() {
  M5.begin();
  M5.Power.begin();
  header("SIM800L AT command", TFT_BLACK);
  M5.Lcd.setTextFont(2);
  M5.Lcd.setTextColor(TFT_WHITE, TFT_BLACK);
  M5.Lcd.drawString("Please use serial port to Test AT command.",0, 35, 2);
  // Host serial communication
  Serial.begin(115200);   

  // SIM800L serial communication
  Serial2.begin(115200, SERIAL_8N1, RX_PIN, TX_PIN);   
  pinMode(RESET_PIN, OUTPUT);
}

void loop() {

  //AT instruction write
  if(Serial.available()){
    Serial2.write(Serial.read());
  }

  //AT instruction result
  if(Serial2.available()){    
    Serial.write(Serial2.read());
  }

  delay(10);

}