Sampling and serial transfer

Question

I am trying to get a sampling rate of over 10k Samples per second as well as send each sample over a serial line. Taking a sample and putting it on the serial line each time took too long. I am using Processing 3.3.6 for datalogging into a csv file. I am unable to achieve more than 6k samples per second even at lower prescaler value and high baudrate. What am I doing wrong? Here is my arduino code.

int val[2000];
void setup()
{
  Serial.begin(250000);

  //ADCSRA = 0;             // clear ADCSRA register
  //ADCSRB = 0;             // clear ADCSRB register
  ADCSRA &= ~(bit (ADPS0) | bit (ADPS1) | bit (ADPS2)); // clear prescaler bits
  //ADCSRA |= bit (ADPS0);                               //   2  
  ADCSRA |= bit (ADPS1);                               //   4  
  //ADCSRA |= bit (ADPS0) | bit (ADPS1);                 //   8  
  //ADCSRA |= bit (ADPS2);                               //  16 
  //ADCSRA |= bit (ADPS0) | bit (ADPS2);                 //  32 
  //ADCSRA |= bit (ADPS1) | bit (ADPS2);                 //  64 
  //ADCSRA |= bit (ADPS0) | bit (ADPS1) | bit (ADPS2);   // 128
  //pinMode(A0, INPUT);

}

void loop()
{
  for(int i=0; i<2000; i++) {
    val[i] = analogRead(A0);
  }
  for(int i=0;i<2000;i++){
    Serial.print(val[i]);
    Serial.print('x');
  }

}

P.S I am new to arduino.

--edit1>> I am using Arduino Mega 2560.

Answer 1

Probably the serial port is too slow:

Assuming 250 kbits/s, is (including 3 start/stop bits, maybe 2 in your case) in about 250000 (bits/s) / 11 (bits/byte)= about 22 KBytes/s Assuming each sample has 3 or 4 digits and an 'x' is added (which is 5 characters), 22 (KBytes/s) / 5 (digits/sample) = about 5-6 Ksamples/s you can transfer, which is what you experienced.

So you have to increase the speed for the serial port.