What difference between Serial.print and saving data into variable?

[system]

Hi Programmers,

I am trying to read data from Futaba servo motor to check a current position.
Some Futaba servo provides TTL communication for control servo motor and read data of current status, position, speed, Id, etc..
I am using Arduino UNO and a serial interface board that I made it using 74HC125. And I am using SoftwareSerial library.
You can see the attached my whole code.

It is working to communicate between my mac and servo motor, sending command to control servo motor and reading a status data from servo.
below code is part of read and display on the serial monitor, it is working.

Serial.print(ServoSerial.read(),HEX);
Serial.print(",");

you can see the attached image "Success to read data"

But I have a problem to read data and save it into variable. When I saved data into variable, it seems there are wrong data.

data = (ServoSerial.read(),HEX);
Serial.print(data*); *
Serial.print(","); [/b]
you can see the attached image "Fail to read #1"
And I tried a different way to read using 'string'
char received = (char)(ServoSerial.read(),HEX); //add
inData += received; //add
inData += ",";
Serial.print(inData); //add
you can see the attached image "Fail to read #2"
I wonder what is difference between using Serial.print with serial monitor and saving data into variable or string.
Please advise or comments for me.
Thank you.
FutabaServoReadTest.ino (2.97 KB)

[Hackscribble]

Hi pwoong

It would help to post your full code (use the code tags - the "#" button above the smileys).

But looking at your extracts, try this:

data = ServoSerial.read();
Serial.print(data, HEX);

Regards

Ray

[system]

HI Ray,

Thank you for quick comment. I tried your suggestion, but it didn't work, same result.

//---------------------------------------------------------------------------
//#include <icrmacros.h>
//#include <NewSoftSerial.h>

#include <SoftwareSerial.h>
SoftwareSerial ServoSerial(2,3);
//NewSoftSerial ServoSerial(2,3);

byte modelnum[]={0xFA, 0xAF, 0x01, 0x0F, 0x00, 0x02, 0x00, 0x0C};
byte currVOLT[]={0xFA, 0xAF, 0x01, 0x0F, 0x34, 0x02, 0x00, 0x38};
byte mem30to41[]={0xFA, 0xAF, 0x01, 0x0B, 0x00, 0x00, 0x01, 0x0B};

  // Servo Restart
 byte ServoReStart[] = {0xFA, 0xAF, 0x0A, 0x20, 0xFF, 0x00, 0x00, 0xDE};
 
 // baudrate 38400
byte baud38400[] = {0xFA, 0xAF, 0x01, 0x00, 0x06, 0x01, 0x01, 0x04, 0x03};
// ROM Write
byte RomWrite[] = {0xFA, 0xAF, 0x01, 0x40, 0xFF, 0x00, 0x00, 0xBE};
// Servo Restart
byte ServoreStart[] = {0xFA, 0xAF, 0x01, 0x20, 0xFF, 0x00, 0x00, 0xDE};

byte readCurrentAngel[] = {0xFA, 0xAF, 0x01, 0x0F, 0x2A, 0x02, 0x00, 0x26}; //Read memory from N0.42 ~ to No.59
byte TrqOn [] = {0xFA, 0xAF, 0x01, 0x00, 0x24, 0x01, 0x01, 0x01, 0x24}; // Torque ON Packet 
byte data[] = {0};
String inData;

void setup()
{
  pinMode(13, OUTPUT);
  ServoSerial.begin(57600);  //It should be less than 57600 to communication
  Serial.begin(57600);
  delay(1000);
 
}

void loop()
{
  int rx, tx;
  
  rx = ServoSerial.available();
  if(rx > 6)
  {
    digitalWrite(13, LOW);
    
    for(int i=0;i<rx;i++)
    {
      //Serial.print(ServoSerial.read(),HEX);
      //Serial.print(",");
      data[i] = (ServoSerial.read(),HEX);  //save serial data to DATA buffer  add
      //char received = (char)(ServoSerial.read(),HEX);   //add
      //Serial.print(received,HEX);  //add
      //Serial.print(",");      //add
      //inData += received;   //add
      //inData += ",";
            
    }
    
    ///*
    for(int i=0;i<rx;i++)   //display on serial monitor  add
    {
      Serial.print(data[i],HEX);  //add
      Serial.print(",");      //add
    } // */
    //Serial.print(inData);  //add
    Serial.print("\n");
    ServoSerial.flush();
  
   
  }
  
   tx = Serial.available();
   if(tx>0) 
   {
      switch(Serial.read()) 
      {
        case 65://"A"
          digitalWrite(13,HIGH);//LED??
          send_msg(modelnum,8);//?????
         
          break;
        case 66://"B"
          digitalWrite(13,HIGH);//LED??
          send_msg(currVOLT,8);//?????
         
          break;
        case 67://"C"
          digitalWrite(13,HIGH);//LED??
          send_msg(readCurrentAngel,8);//?????30??41
          
          break;
        case 68://"D"
          digitalWrite(13,HIGH);//LED??
          send_msg(mem30to41,8);
          
          break;
        default:
          for(int i=0;i<4;i++) 
          {
            digitalWrite(13,HIGH);
            delay(200);
            digitalWrite(13,LOW);
            delay(200);
          }
          break;
      }
      Serial.flush();//????????
    }
 }

void send_msg(byte msg[], int n) {
  ServoSerial.write(msg,n);
   
}

//---------------------------------------------------------------------------

[Hackscribble]

byte data[] = {0};

This creates a 1-element array of byte and initialises that 1 element to 0.

You will need to decide how many bytes you need to store in data and declare it with at least that size. For example:

#define BUFFER_SIZE 32
...
byte data[BUFFER_SIZE] = {0};

And don't forget to change the Serial.read() statements to this:

data[i] = ServoSerial.read();

[system]

Thank you.

It is working now!!