LCD shows unwanted text like DDDDDDDDDDDDDDDD

Other Hardware Displays
1

I have a draft version of a voltage logger with and SD card writer, which shows it's sensor values also on an LCD display.
When I write the first text "Initializing SD" to the LCD, it appears as it should. But when I then write "SD Card ok", it shows
DDDDDDDDDDDDDDDD
DDDDDDDDDDDDDDDD

All other LCD sample programs work fine so I think the connections are ok. And the rest of the program also works as it should.

Any idea what I'm doing wrong?

// Voltage Logger

// include the library code:
#include <LiquidCrystal.h>
#include <RTClib.h>
#include <SD.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int chipSelect = 10, count = 0;
String dataString = "", fileName = "", dtString = "";

float voltage = 0.0;

RTC_DS1307 rtc;

void setup() {
  Serial.begin(9600);

  if (! rtc.begin()) {
    Serial.println("Couldn't find RTC");
    Serial.flush();
    while (1) delay(10);
  }

  //rtc.adjust(DateTime(2023,3,31,18,43,0));
 
  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("Initializing SD ");

  Serial.println("\nInitializing SD Card");
  delay(1000);

  while (!SD.begin(chipSelect)) {
    Serial.println("SD Card failed");
    lcd.setCursor(0, 1);
    lcd.print("SD Card Failed  ");
  }
  Serial.println("SD Card initialized");
  lcd.setCursor(0, 1);
  lcd.print("SD Card ok      ");
  delay(1000);
}

void loop() {
  DateTime now = rtc.now();
  dtString = String(now.hour()) + ":" + String(now.minute()) + ":" + String(now.second());

  int sensorValue = analogRead(A0);
  float voltage = sensorValue * (5.0 / 1023);
  Serial.print(dtString); Serial.print(" - "); Serial.print(String(voltage, 2)); Serial.println(" V");

  lcd.setCursor(0, 0);
  lcd.print(dtString);
  lcd.setCursor(0, 1);
  lcd.print(String(voltage, 2));

  fileName = "datalog.csv";
  File dataFile = SD.open(fileName, FILE_WRITE);
  if (count == 0)
    dataFile.println("Time,Voltage");
  dataString = dtString + "," + String(voltage, 2);
  dataFile.println(dataString);
  dataFile.close();
  delay(1000);
  count++;
}
2

Are you sharing pins between the SD card and LCD?

3

SPI library is included by SD.h, so SPI is being used. Pin 11 is MOSI an pin 12 is MISO.

4

I'm using a Velleman shield on top of an Arduino UNO, so indeed maybe using the same pins. I'll disable the SD functions and try again.

5

Yes, now it's working fine. So SD card and LCD cannot be combined? Or should I use other pins?

6

The SD library has a way to specify the pins for CS, SCK, MOSI and MISO by adding parameters to the begin function.

boolean begin(uint8_t csPin = SD_CHIP_SELECT_PIN, int8_t mosi = -1, int8_t miso = -1, int8_t sck = -1);

May be a way to go since changing the hardwired LCD shield pins would be difficult.

7

I changed the pins like LiquidCrystal lcd(8, 7, 5, 6, 3, 2); and rewired accordingly and it works fine.

Thanks a lot all!

8

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