I think you want something like this:
#include <LiquidCrystal_I2C.h>
#include <Wire.h>
LiquidCrystal_I2C lcd(0x03f, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); // Set the LCD I2C address
//LiquidCrystal_I2C lcd(0x03f, 20, 4); // Set the LCD address, columns, and rows
byte DMM_ARRAY[14]; // Where to store the Bytes read
const int ledPin = 13; // Set the pin to digital I/O
const byte Segments[] = {0x7D, 0x05, 0x5B, 0x1F, 0x27, 0x3E, 0x7E, 0x15, 0x7F, 0x3F, 0x00, 0x68};
const char Digits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ' ', 'L'};
void setup() {
lcd.begin (20, 4); // for 16 x 2 LCD module
lcd.setBacklight(HIGH);
pinMode(ledPin, OUTPUT);
Serial.begin(2400);
}
void loop() {
Get_data();
//print the hex bytes to the display
lcd.setCursor(0, 0);
lcd.print(DMM_ARRAY[0], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[1], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[2], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[3], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[4], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[5], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[6], HEX);
lcd.setCursor(0, 1);
lcd.print(DMM_ARRAY[7], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[8], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[9], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[10], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[11], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[12], HEX);
lcd.print(",");
lcd.print(DMM_ARRAY[13], HEX);
// Process two bytes for each of four digits, starting at offset 1
lcd.setCursor(3, 3);
for (int index = 0; index < 4; index += 2) {
byte segments = (DMM_ARRAY[index*2+1] << 4) | DMM_ARRAY[index*2+2] & 0x0F;
if (segments & 0x80) { // Negative/Decimal flag set
if (index == 0)
lcd.print("-"); // Negative flag
else
lcd.print("+"); // Decimal flag
}
lcd.print(getDigit(segments & 0x7F));
}
}
void Get_data() {
while (Serial.available() < 14) {} // Wait 'till there are 14 Bytes waiting
for (int n = 0; n < 14; n++)
DMM_ARRAY[n] = Serial.read(); // Then: Get them.
}
char getDigit(const byte segments) {
for (byte i = 0; i < sizeof Segments / sizeof Segments[0]; i++) {
if (Segments[i] == segments)
return Digits[i];
}
return '?';
}