Communication between two boards

Using Arduino Programming Questions
1

Hi everyone
I am new at programming and encountered a problem that I need experienced people like you to help to solve.

I have two arduino boards(M0 PRO and UNO). What I would like to do is transmit variables from M0 PRO to UNO which is connected to a screen(1.8" TFT shield, Adafruit), therefore those variables will be shown on the screen.

For testing, I simply tried to make "blank" shown on the screen while it did not work,below are what I wrote

M0 PRO

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

void loop() {
  Serial.write("100");
  delay(50);        // delay in between reads for stability
}

UNO

float p = 3.1415926;
int pr = 0;
int oldpr = 0;
String prs = "empty";

}

void loop() {

  prs = Serial.readStringUntil('\n');

  String output = "Pressure kPa: " + prs ;
  
  tft.fillRect(85, 5, 30, 10, ST7735_BLACK);

  tft.setCursor(5, 5);
  tft.setTextColor(ST7735_WHITE);
  tft.setTextSize(1);
  tft.println(output);
  
  delay(2000);

}

It will be a great help
Thank you very much :slight_smile:

2

Can you explain the connection between two arduino? How the serial pins connected on both Arduino?

3

One end reads data until it encounters a \n. The other end does not send a \n. Why not?

4

Have a look at the examples in Serial Input Basics - simple reliable ways to receive data. There is also a parse example.

The 3rd example will be the most reliable and you should easily be able to make the sending Arduino comply with that system.

...R

5

If you have two boards, would you consider using 2-wire protocol? For programming, 2-wire is nice because it sends packets rather than individual characters that you have to parse as they come in.

6

PaulS:
One end reads data until it encounters a \n. The other end does not send a \n. Why not?

Did you check this suggestion from PaulS?
Have you went through Robin's tutorial, Post #3
How did you connect both Arduino's
Do they have common GND?
Arduino1->Arduino2

TX->RX
RX->TX
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