Problem with Serial communication

Projects Programming
1

Hello,
I have problem with my OLIMEXINO-NANO (ATMEGA32U4 Arduino Leonardo compatible) with MOD-RS232 (MAX3232CDR chip by TI).

I wanted to send 10bytes (for example 10 times 0x00) using Serial1.write function. Below is my code:

byte byteOne[10] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

void setup()
{
  Serial.begin(9600);
  Serial1.begin(9600);
}
void loop()
{
  if (Serial.available() > 0)
  {
    Serial.read();
    Serial.write(byteOne, 10);
    Serial1.write(byteOne, 10);
  }
}

To send frame, any data on USB must have been sent.
The problem is that - on USB channel (Serial) I have proper frame with 10x 00, but on RS232 (Serial1) only first 4 bytes are zeros and the rest are random:

Have anyone meet the same problem?

How can I "repair" my code to avoid this situation?

simple.ino (251 Bytes)

2

The problem is that - on USB channel (Serial) I have proper frame with 10x 00, but on RS232 (Serial1)

Serial1 is NOT a RS232 port. What IS connected to the RX1 and TX1 pins?

3

PaulS:
Serial1 is NOT a RS232 port. What IS connected to the RX1 and TX1 pins?

I connected them to port#1 on my computer - physical RS232 on DB9 without any adapters.

4

OK, I managed with problem. I modified my code:

byte byteOne[10];

void setup() {
  // initialize both serial ports:
  Serial.begin(9600);
  Serial1.begin(9600);

}

void loop() {
  static int j = 0;
  if (Serial.available())
  {
    // read from port 0, send to port 1:
    char ch = Serial.read();
    byteOne[j] = ch - '0';
    j++;
    if (Serial.available() == 0)
    {
      for (int i = 0; i < 10; i++)
      {
        delay(2);
        Serial1.write(byteOne[i]);
      }
      j = 0;
    }
  }
}

I didn't change electrically anything. I put only delay (2ms) between each bytes and it started work properly. Delay 1ms is not enough, so I think there was a problem.

5 
  if (Serial.available())
  {
    // read from port 0, send to port 1:
    char ch = Serial.read();
    byteOne[j] = ch - '0';
    j++;
    if (Serial.available() == 0)
...

You have a race condition here, I would not advise doing it this way.

6
7 
  if (Serial.available())
  {
...
    char ch = Serial.read();
...
    if (Serial.available() == 0)

What if two bytes are available? It passes the first test but not the second.

8

Have a look at the examples in serial input basics

...R

9

OK, sorry for last code:

byte byteOne[10] ={0,0,0,0,0,0,0,0,0,0};

void setup() {
  // initialize both serial ports:
  Serial.begin(9600);
  Serial1.begin(9600);

}

void loop() {
  static int j = 0;
  if (Serial.available())
  {
    Serial.read();
    if (Serial.available() == 0)
    {
      for (int i = 0; i < 10; i++)
      {
        Serial1.write(byteOne[i]);
      }
    }
  }
}

On this code, on Serial1 I'm not sending 10 bytes each 0x00, but after 4th bytes there is random (I guess) values. This is my problem. I know that if I type 2 bytes, it will not working properly.

10

Exactly as I predicted. Did you read: Gammon Forum : Electronics : Microprocessors : How to process incoming serial data without blocking ?

11

Yes, I read that now. I get it. Nevertheless I still has a problem with sending frame using Serial1, as I write. I modify my sketch to only send frame per 1 second and it is still sending "random" values even I assign all bytes in frame:

byte byteOne[10] ={0,0,0,0,0,0,0,0,0,0};

void setup() {

  Serial1.begin(9600);

}

void loop() {
      delay(1000);
      for (int i = 0; i < 10; i++)
      {
        Serial1.write(byteOne[i]);
      }
  
}