cattledog:
Here are two inter-Arduino i2c send and receive sketches written for a 16x2 lcd display. It sends Time and dummy temperature data. The receive portion is adapted from the methods of Robin2's tutorial on serial data. Serial Input Basics - #2 by Robin2 - Programming Questions - Arduino Forum
You can probably adapt parts of it for your purposes. Master sends data, slave controls lcd display.
#include <Wire.h>//must be before RTClib
#include <RTClib.h>
RTC_DS1307 RTC;
int interval = 2000;
unsigned long lastSend;
void setup()
{
Wire.begin();
RTC.begin();
}
void loop()
{
if (millis() - lastSend >= interval)
{
DateTime now= RTC.now();
char timeChars[8];
sprintf(timeChars,"%02d:%02d:%02d", now.hour(),now.minute(),now.second());
static float T = 19.0;//dummy temperature float variable
char tempChars[4];//will hold xx.x
dtostrf(T,4,1,tempChars);
Wire.beginTransmission(1); //to slave device 1
Wire.write('<'); //startMarker
Wire.write("Time ");//can put in slave sketch
Wire.write(timeChars);
Wire.write("&"); //separator for line1/line2 parse on rx
Wire.write("Temp C "); //can put in slave sketch
Wire.write(tempChars);
Wire.write('>'); //endMarker
Wire.endTransmission(); // send complete data package
lastSend = millis();
T += .1; //change value sent
if (T >= 25) T = 19;
}
}
Receive
#include<Wire.h>
#include <LiquidCrystal_I2C.h> // F Malpartida's NewLiquidCrystal library
LiquidCrystal_I2C lcd(0x20, 4, 5, 6, 0, 1, 2, 3, 7, NEGATIVE);
const byte SlaveDeviceId = 1;
const byte numChars = 32; //max 32 for 16x2 lcd display
char receivedChars[numChars];
boolean newData = false;
char* line1; //for 2 line lcd display
char* line2;
void setup() {
Wire.begin(SlaveDeviceId);
lcd.begin (16, 2);
lcd.print(F("XXXXXXXXXXXXXXXX"));//visual cue for setup
lcd.setCursor(0, 1);
lcd.print (F("XXXXXXXXXXXXXXXX"));
delay(2000);
lcd.clear();
//could print unchanging parts of line1 and line2 here
Wire.onReceive(receiveEvent);
}
void loop() {
if (newData == true) {
line1 = strtok(receivedChars, "&"); //parse line 1
line2 = strtok(NULL, "\0"); //parse line2
lcd.clear();
lcd.setCursor(0, 0);
lcd.print(line1);
lcd.setCursor (0, 1);
lcd.print(line2);
newData = false;
}
}
//Serial receive from Robin2 forum post Serial Input Basics - #2 by Robin2 - Programming Questions - Arduino Forum
void receiveEvent(int bytesReceived)
{
static boolean recvInProgress = false;
static byte ndx = 0;
char startMarker = '<';
char endMarker = '>';
char rc;
while (Wire.available() > 0 && newData == false) { //get all bytes from buffer
rc = Wire.read();
if (recvInProgress == true) {
if (rc != endMarker) {
receivedChars[ndx] = rc;
ndx++;
if (ndx >= numChars) {
ndx = numChars - 1;
}
}
else {
receivedChars[ndx] = '\0'; // terminate the string
recvInProgress = false;
ndx = 0;
newData = true;
}
}
else if (rc == startMarker) {
recvInProgress = true;
}
}
}
Thank you, i was able to load that with some mods and print I2C data on the receiver.
the problem is that I2C data being sent to the LCD is probably a different format in some way, and that is what i need to print.
i do NOT need to print I2C data being sent from Arduino 1 to Arduino 2.
i DO need to serial print the data sent from Arduino 2 to the LCD, via serial monitor as string or char.
When i configured the codes to Tx and Rx on address 0x38, boh Arduinos communicate fine and data flows and prints.
When i connected the Arduino 2 (receiver) to my ECU (which is sending Data to LCD address 0x38 constantly) it never goes into the "if data == true" loop. dontknow why.
any idea how to do that? im still looking 
appriciate the help very much, thank you guys.