T-Display-S3 UART communication issue

eflorea

I have this device : SIM7600G-H, that I know works because I started my initial tests on the Arduino UNO, and I was able to get an "OK" from a basic status check ("AT" command), I could send SMS, make a call...everything on the UNO is working great.

Moving over to the T-Display-S3, I can't get anything out of the unit, not even an "OK", I trimmed the code down to the basic instructions that should work.

I have tried the Serial Example, posted in the Github repo, and that works, so I can see the data I enter into the Serial Monitor to pass through the ports, so I would think everything is okay, but then why would it not work on the T-Display S3, but work on the Arduino UNO ???

I tried other ports 21, and 16, as shown in the Github repo example, and that didn't work...Running out of ideas here, if anyone has had issues implementing a Hardware Serial build please let me know.

Thank You.

#define RX_PIN 18
#define TX_PIN 17

#define SIMCOM Serial1

const long int SIMCOM_BITRATE = 115200;

void setup() {

  Serial.begin(115200);
  
  while (!Serial) {
    ; 
  }
  delay(3000);

  SIMCOM.begin(SIMCOM_BITRATE, SERIAL_8N1, RX_PIN, TX_PIN);
  while (!SIMCOM) {
    ; 
  }  
  delay(3000);

}

void loop() {

  char message[] = "AT";

  SIMCOM.write(message);

  Serial.println(message);

  delay(100);

  long int time = millis();

  int timeout = 5000;
  
  int x = 0;
  char response[128];

  do {

    if (SIMCOM.available() != 0 ) {
        response[x] = SIMCOM.read();
        x++;
    }

  } while ((time + timeout) > millis());

  Serial.println("Timed out..." + String(x));

  Serial.print("Response : ");
  Serial.println(response);
  Serial.println();

}

eflorea

Little update.

I am able to receive the initialization message from the SIM7600 board, so at least I know that the hardware serial read works :

RDY

+CPIN: READY

SMS DONE

PB DONE

If anyone has this issue, you can just do a read in the main loop....

  String response = "";

  while (SIMCOM.available()) {
     char c = SIMCOM.read();
     response += c;
  }
  Serial.print(response);

and then power cycle the SIM7600 with The T-Display-S3 connected

Still a mystery as to what is going on