Splitting byte array or assign value directly from serial?

[jatox]

Hi all,

I'm receiving 16 bytes from a sensor via serial and I want to assign the last 8 to 4 seperate variables pairwise so 2 bytes per variable.
These are my bytes printed out as an array.

84 68 65 84 0 0 0 0 1 0 0 0 82 82 65 73

Is it possible to assign the bytes to variables directly from serial or do I have to put it all into an array and split it?

This is how I do it now and it "sort of" works but it seems messy.

      Serial1.readBytes(resp_frame1, 8);
      byte TDAT_Distance[2];
      Serial1.readBytes(TDAT_Distance, 2);
      byte TDAT_Speed[2];
      Serial1.readBytes(TDAT_Speed, 2);
      byte TDAT_Angle[2];
      Serial1.readBytes(TDAT_Angle, 2);
      byte TDAT_Magnitude[2];
      Serial1.readBytes(TDAT_Magnitude, 2);

Any hints are greatly appreciated!

[CrossRoads]

I would capture them all, and then split them up

for (x = 0; x <4; x=x+1){
intArray[x] = byteArray[(x*2)<<8 | array[(x*2)+1]; // or x+1, x, depends which is upper
}  // 0 1, 2  3,  4  5,  6  7

[GolamMostafa]

Another approach that may help:

while(Serial.available() < 8)
{
    (void)Serial.read();   //discard first 8-bytes

}

/*int y1 = Serial.read()<<8|Serial.read(); //assuming MSByte arrives first[/s]
[s]int y2 = Serial.read()<<8|Serial.read();[/s]
[s]int y3 = Serial.read()<<8|Serial.read();[/s]
[s]int y4 = Serial.read()<<8|Serial.read();*/

//above lines are replaced by the following codes in respect of Post-6, 7, 9.

for(int i =0; i<4; i++)
{
     byte msb = Serial.read();   //assuming msb arrives first
     byte lsb = Serial.read();
     saveArray[i] = msb<<8|lsb;     //saveArray[] is an int type array
}

[Robin2]

If you create a struct with the appropriate variables in it for the complete message then if you copy the message into the struct all the values will be available for use.

See how the struct is created and used in this example

...R

[jatox]

Thank you all for the answers! I will have to test my way forward.

The incoming bytes are all LSB, how does that affect the above examples?

[jatox]

Intuitively, using the struct approach seem like the cleaner way to do this? However I need to read up on it to understand it properly.
Btw, I need the first 8 bytes as well for reading whether there's a registered target.

I tried reading the last 8 bytes into 4 2 byte arrays and convert them to integers and I get what seems like correct readings. Is this wrong?

      byte TDAT_Distance[2];
      Serial1.readBytes(TDAT_Distance, 2);
      unsigned int distance = ((TDAT_Distance[1]<<8)+TDAT_Distance[0]);

[christop]

GolamMostafa:
Another approach that may help:

while(Serial.available() < 8)

{
   (void)Serial.read();   //discard first 8-bytes

}
int y1 = Serial.read()<<8|Serial.read(); //assuming MSByte arrives first
int y2 = Serial.read()<<8|Serial.read();
int y3 = Serial.read()<<8|Serial.read();
int y4 = Serial.read()<<8|Serial.read();

The compiler doesn't guarantee that the first Serial.read() in each statement is executed first. Changing the compiler version or even the optimization level might break your program if you rely on the order of execution like this.

[PaulRB]

christop:
The compiler doesn't guarantee that the first Serial.read() in each statement is executed first. Changing the compiler version or even the optimization level might break your program if you rely on the order of execution like this.

+1, this is correct.

Could use this:

int readWord() {
  byte msb = Serial1.read();
  byte lsb = Serial1.read();
  return word(msb, lsb);
}

[GolamMostafa]

christop:
The compiler doesn't guarantee that the first Serial.read() in each statement is executed first. Changing the compiler version or even the optimization level might break your program if you rely on the order of execution like this.

1. Serial Buffer (Fig-1) of the UART Port is a FIFO (first-in first-out) type buffer. So, consecutive Serial.read() operations should always bring out data byte from the topmost location of the buffer.

2. Do you want to mean that the order of execution of the following two read() operations may not be from left to right?

int y1 = Serial.read()<<8|Serial.read(); //assuming MSByte arrives first

3. Serial Buffer of UART Port

Figure-1:

[Coding_Badly]

GolamMostafa:
2. Do you want mean that the order of execution of the following two read() operations may not be from left to right?

https://www.google.com/search?q=c%2B%2B+function+call+out+of+order

https://en.cppreference.com/w/cpp/language/eval_order

[GolamMostafa]

[quote author=Coding Badly date=1611817337 link=msg=4875798]
https://en.cppreference.com/w/cpp/language/eval_order[/quote]