Mega 2560, 2.4" LCD shield, plus GPS

Other Hardware Displays
1

I have a project that uses an Arduino Mega 2560 with a 2.4" LCD shield that I want to use a GPS on one of the serial ports. The GPS works fine without the shield as it gives a lot of information on the serial monitor but will not show the information on the LCD shield until some time (20-30 minutes or more) has passed and then the location will not update as I move about. I have tried it on Serial 1 and Serial 2 with the same results, changing the coding to reflect the different serial ports. The soil fertility sensor works fine and displays the proper information.

I have worked around this problem by adapting it to an ESP32 so it isn't critical that I get an answer.

[code]
#include <Adafruit_GFX.h>
#include <MCUFRIEND_kbv.h>
#include <TinyGPSPlus.h>
#include <SPI.h>
#include <SD.h>
File myFile;
TinyGPSPlus gps; // create gps object
MCUFRIEND_kbv tft;

#define  BLACK   0x0000
#define RED     0xF800
#define YELLOW  0xFFE0
#define TFT_GREENYELLOW 0xB7E0      /* 180, 255,   0 */
#define TFT_PINK        0xFC9F
#define TFT_MAGENTA     0xF81F 

#define LCD_CS A3
#define LCD_CD A2
#define LCD_WR A1
#define LCD_RD A0
#define LCD_RESET A4

//#define RE 8
//#define DE 7

const int DIN_PIN = 23;
String gpstext;



//const byte code[]= {0x01, 0x03, 0x00, 0x1e, 0x00, 0x03, 0x65, 0xCD};
const byte nitro[] = {0x01, 0x03, 0x00, 0x1e, 0x00, 0x01, 0xe4, 0x0c};
const byte phos[] = {0x01, 0x03, 0x00, 0x1f, 0x00, 0x01, 0xb5, 0xcc};
const byte pota[] = {0x01, 0x03, 0x00, 0x20, 0x00, 0x01, 0x85, 0xc0};

byte values[11];

void setup() {

  Serial.begin(115200);
  Serial1.begin(9600);
  Serial1.begin(9600);
 
  pinMode( DIN_PIN, INPUT_PULLUP );

  tft.reset();
  tft.begin(0x9341);
  tft.setRotation(1);
  tft.fillScreen(BLACK);

  if (!SD.begin()) {
    Serial.println("fail");
    tft.setTextColor(TFT_PINK );
    tft.setCursor(160, 100);
    tft.setTextSize(3);
    tft.print("No SD");
    delay(15000);
    tft.setTextColor(BLACK);
    tft.setCursor(160, 100);
    tft.setTextSize(3);
    tft.print("No SD");
  }
  else {
     if (SD.exists("/Filed.csv"))
    {
    }
    File myFile = SD.open("Field.csv", FILE_WRITE);

    myFile.print("Latitude");
    myFile.print(", ");
    myFile.print("Longitude");
    myFile.print(", ");
    myFile.print("Nitrogen");
    myFile.print(", ");
    myFile.print("Phosphorus");
    myFile.print(", ");
    myFile.println("Potash");
    myFile.close();
  }
}

void loop() {
  int value;

  byte val1, val2, val3;
  val1 = nitrogen();
  delay(250);
  val2 = phosphorous();
  delay(250);
  val3 = potassium();
  delay(250);


 while (Serial2.available() > 0)
    if (gps.encode(Serial2.read())) {
     if (displayInfo() != "0")
      {
 
        // Get GPS string
        gpstext = displayInfo();
 
        
      }
    }
    
  tft.setTextColor(YELLOW);
      tft.setCursor(7, 10);
      tft.setTextSize(2);
      tft.print("Latitude");
      tft.setCursor(135, 10);
      tft.print("Longitude");
      tft.setCursor(270, 10);
      tft.print("Sats");
      tft.fillRect(5, 40, 320, 20, BLACK);
      tft.setCursor(5, 40);
      tft.setTextColor(YELLOW);
      tft.print(gpstext);
      tft.setCursor(125, 40);
      //tft.print(String(longi));
  tft.setCursor(7,90);
  tft.setTextSize(3);
  tft.print("N:");
  tft.fillRect(45, 90,52,25,BLACK);
  tft.setCursor(45, 90);
  tft.setTextColor(YELLOW);
  tft.print(val1);
  tft.setCursor(7, 140);
  tft.print("P:");
  tft.fillRect(45,140,52,25,BLACK);
  tft.setCursor(45, 140);
  tft.setTextColor(YELLOW);
  tft.print(val2);
  tft.setCursor(7, 190);
  tft.print("K:");
  tft.fillRect(45, 190,52,25,BLACK);
  tft.setCursor(45, 190);
  tft.setTextColor(YELLOW);
  tft.print(val3);
  
  value = digitalRead(DIN_PIN);
  Serial.println(value);

  if (value < 1) {
    Serial.println(value);

    File myFile = SD.open("Field.csv", FILE_WRITE);

    // if the file is available, write to it:
    // if (myFile) {
    myFile.print(gpstext);
//    myFile.print(", ");
//    myFile.print(longi);
    myFile.print(", ");
    myFile.print(val1);
    myFile.print(", ");
    myFile.print(val2);
    myFile.print(", ");
    myFile.println(val3);
    myFile.close();


    tft.setTextColor(TFT_MAGENTA );
    tft.setCursor(150, 100);
    tft.setTextSize(3);
    tft.print("Recording");
    delay(1000);
    tft.setCursor(150, 130);
    tft.print("Recording");
    delay(1000);
    tft.setCursor(180, 160);
    tft.print("DONE!");
    delay(2000);

    tft.setTextColor(BLACK);
    tft.setCursor(150, 100);
    tft.setTextSize(3);
    tft.print("Recording");
    tft.setCursor(150, 130);
    tft.print("Recording");
    tft.setCursor(180, 160);
    tft.print("DONE!");

    // }
  }



  delay(1000);
}

byte nitrogen() {
  // digitalWrite(DE, HIGH);
  //  digitalWrite(RE, HIGH);
  delay(10);
  if (Serial1.write(nitro, sizeof(nitro)) == 8) {
    //   digitalWrite(DE, LOW);
    //   digitalWrite(RE, LOW);
    for (byte i = 0; i < 7; i++) {
      //Serial.print(mod.read(),HEX);
      values[i] = Serial1.read();
      //     Serial.print(values[i], HEX);
    }
    //   Serial.println();
  }
  return values[4];
}

byte phosphorous() {
  //  digitalWrite(DE, HIGH);
  //  digitalWrite(RE, HIGH);
  delay(10);
  if (Serial1.write(phos, sizeof(phos)) == 8) {
    //    digitalWrite(DE, LOW);
    //   digitalWrite(RE, LOW);
    for (byte i = 0; i < 7; i++) {
      //Serial.print(mod.read(),HEX);
      values[i] = Serial1.read();
      //      Serial.print(values[i], HEX);
    }
    //    Serial.println();
  }
  return values[4];
}

byte potassium() {
  //  digitalWrite(DE, HIGH);
  //  digitalWrite(RE, HIGH);
  delay(10);
  if (Serial1.write(pota, sizeof(pota)) == 8) {
    //    digitalWrite(DE, LOW);
    //    digitalWrite(RE, LOW);
    for (byte i = 0; i < 7; i++) {
      //Serial.print(mod.read(),HEX);
      values[i] = Serial1.read();
      //     Serial.print(values[i], HEX);
    }
    //  Serial.println();
    return values[4];
  }
}

String displayInfo()
{
  // Define empty string to hold output
   String gpsdata = "";
 
  // Get latitude and longitude
  if (gps.location.isValid())
  {
  gpsdata = String(gps.location.lat(), 6);

    gpsdata += (", ");
    gpsdata += String(gps.location.lng(), 6);
    gpsdata += (", ");
    gpsdata += String(gps.satellites.value());
  }
  else
  {
    return "0";
  }

   // Return completed string
  return gpsdata;
}
[/code]
2

Your major problem is the use of delay(). At 9600 baud, the input from the GPS will fill the serial input buffer in approximately 65mS, anything longer than that will result in a buffer overflow and lost data. Writing to the SD card can also introduce enough delay to be a problem.

Are you able to configure the GPS to only send the necessary NMEA sentences? TInyGPS only uses the RMC and GGA sentences. If you can set the GPS to send only those, and possibly increase the baud rate, then you will have a long interval between data from the GPS in order to run other parts of the code.

3

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