#include <M5Stack.h>
#include <M5LoRa.h>

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();
                  // initialize serial
  header("LoRa Receiver Callback", TFT_BLACK);
  M5.Lcd.setTextFont(2);
  M5.Lcd.setTextColor(TFT_WHITE, TFT_BLACK);
  M5.Lcd.drawString("Please use serial port to view data.",0, 35, 2);
  Serial.println("LoRa Receiver Callback");

  // frequency in Hz (433E6, 866E6, 915E6)
  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }

  // register the receive callback
  LoRa.onReceive(onReceive);

  // put the radio into receive mode
  LoRa.receive();
}

void loop() {
  // do nothing
  LoRa.receive();
}

void onReceive(int packetSize) {
  // received a packet
  Serial.print("Received packet '");

  // read packet
  for (int i = 0; i < packetSize; i++) {
    Serial.print((char)LoRa.read());
  }

  // print RSSI of packet
  Serial.print("' with RSSI ");
  Serial.println(LoRa.packetRssi());
}