receive multiple serail data in simulink frm arduino without delay

Hi Every one

I am using Matlab 2018 to receive multiple data from arduino. The Serial Receive block in Matlab 2018 has the pssibility of defining number of received data. So if I want to receive multiple data of size 2 (for examp.), I will set the data lenght to 2. However, If I try to send an array using the following code in arduino:

int a=10;
int b=20;
char c[2] = {a,b};
void setup() {
Serial1.begin(9600);
}

void loop() {
Serial1.write(c);
delay(100);
}

and use the fllowing simple simulink code to receive the array in simulink:

I receive the folloing error:

Build process completed successfully
Error occurred while executing External Mode MEX-file 'ext_comm':
ExtTargetPktPending() call failed while checking  for target pkt

If I try to send the array elements seperately in arduino like as:

int a=10;
int b=20;
void setup() {
Serial1.begin(9600);
}

void loop() {
Serial1.write(a);
Serial1.write(b);
delay(100);
}

again I receive the same error. However, if I use a delay between every two data like as:

int a=10;
int b=20;
void setup() {
Serial1.begin(9600);
}

void loop() {
Serial1.write(a);
delay(100);
Serial1.write(b);
delay(100);
}

then the receive block in simulink works correctly an I can get the data. But it makes no sense for me to send multiple data with delays between them. I need to send all of may data simultaneously. I just can have one delay (equal to my time step )at the end of sending all data synchronously.

Also, I should mention that if I set the delays equal to small vaclues(like 10ms), again I receive the same error.

I would appreciate if some one helps me on this.

[Walter Roberson]

char c[2] = {a,b};

That is not a byte.

That is not a string: it is not null terminated.

Serial1.write(c);

You can write() a byte or you can write a string.

Answer 1

[elham modaresi]

Hi Walter

Tanks for your comment.

I modify the code as:

byte c[2];
c[0] =10;
c[1]=20;
void setup() {
Serial1.begin(9600);
}

void loop() {
Serial1.write(c,2);
//delay(10);
//Serial1.write(b);
delay(100);
}

Arduino gets an erre: 'c' does not have a type.

Could u pls modify it?

[Walter Roberson]

Please post the exact error message on the arduino side.

[Arun Kumar]

Move the assignment inside setup or loop, it should work fine.

byte c[2];
void setup() {
  c[0] =10;
  c[1]=20;
  Serial1.begin(9600);
}
void loop() {
  Serial1.write(c,2);
  //delay(10);
  //Serial1.write(b);
  delay(100);
}

[elham modaresi]

I modify the arduino code as:

byte c[2];
void setup()
{
  c[0] = 10;
  c[1] = 20;
  Serial1.begin(9600);
}
void loop()
{
Serial1.write(c, 2);
delay(100);
}

Now I do not get an an arduino error. but still I cannot receive the data in receive block in simulink I get the same error:

Build process completed successfully
Error occurred while executing External Mode MEX-file 'ext_comm':
ExtTargetPktPending() call failed while checking  for target pkt

also I tested the code like this:

byte a =10;
byte b= 20;
void setup()
{
  Serial1.begin(9600);
}
void loop()
{
Serial1.write(a);
Serial1.write("\n");
Serial1.write(b);
delay(100);
}

again same error I got.

It only works when I set a delay between two data.

But this is not possible for me. I wil also attach my simulink code in case.

Thanks,

Answer 2

[Arun Kumar]

Hi,

This code should work fine. I've checked with Arduino Uno and Mega

int a=10;
int b=20;
void setup() {
Serial1.begin(9600);
}
void loop() {
Serial1.write(a);
Serial1.write(b);
delay(100);
}

Delay is not required in between serial writes.

[elham modaresi]

This code does not worked for me. pls see the simulink code I attached before.

Answer 3

[elham modaresi]

but this does not work for me. I get the same error I mentioned before. I am using arduino Due. But I do not think this would make a problem.

I will attach my simulink code.

Could u pls have a look at it. Thanks in advance.

[elham modaresi]

Also this is my Arduino code, which I moved the assignment into the void set up:

void setup()
{
  byte c[2];
  c[0] = 10;
  c[1] = 20;
  Serial1.begin(9600);

  

}

void loop(){
Serial1.write(c, 2);
delay(100);
{

Arduino says:

Arduino: 1.8.9 (Windows 7), Board: "Arduino Due (Programming Port)"

D:\MyProjects\Robot\Arduino\test\test.ino: In function 'void loop()':

test:14:15: error: 'c' was not declared in this scope

 Serial1.write(c, 2);

               ^

test:16:1: error: expected '}' at end of input

 {

 ^

test:16:1: error: expected '}' at end of input

exit status 1
'c' was not declared in this scope

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

[Arun Kumar]

You need to move only the assignment, not the declaration. Since you are using the same variable in loop function also.

[elham modaresi]

I fixed the arduino code. It wont work without delays between data. How can I fix it please?