Sampling rate issue

Question

I have an Arduino code which runs decently.

// Read in 10-bits Magnetic Encoder AEAT-6010-A06  into Arduino Uno
// Sampling

// Declarate

const int CSn = 4; // Chip select
const int CLK = 7; // Clock signal
const int DO = 8; // Digital Output from the encoder which delivers me a 0 or 1, depending on the bar angle..
int analogPin = 3;
int val = 0;
unsigned int sensorWaarde = 0;

void setup() {
  Serial.begin(115200);
  //Fix de tris

  pinMode(CSn, OUTPUT);
  pinMode(CLK, OUTPUT);
  pinMode(DO, INPUT);

  //Let's start here
  digitalWrite(CLK, HIGH);
  digitalWrite(CSn, HIGH);
}



void loop() {

  val = analogRead(analogPin);
  // val = val - 670;
  sensorWaarde = readSensor();
  delayMicroseconds(1); //Tcs waiting for another read in
}

unsigned int readSensor() {
  unsigned int dataOut = 0;

  digitalWrite(CSn, LOW);
  delayMicroseconds(1); //Waiting for Tclkfe

  //Passing 10 times, from 0 to 9
  for (int x = 0; x < 10; x++) {
    digitalWrite(CLK, LOW);
    delayMicroseconds(1); //Tclk/2
    digitalWrite(CLK, HIGH);
    delayMicroseconds(1); //Tdo valid, like Tclk/2
    dataOut = (dataOut << 1) | digitalRead(DO); //shift all the entering data to the left and past the pin state to it. 1e bit is MSB
  }

  digitalWrite(CSn, HIGH); //
  Serial.print(dataOut);
  Serial.print("");
  Serial.print(" ");
  Serial.println(val);
  Serial.print(" ");

  delay(2);
  return dataOut;

}

From the delay data i assumed that i will be having approximately a sampling rate of 500 Hz, however it seems that the sampling rate is approximately 300+- Hz, without a proper confirmation.

My system is to be run in a Magnetic Encoder by Avago, but i have difficulties determining the sampling rate.

If possible, may i know what code should i use to indicate the time and sampling number?

Answer 1

At 115200 baud your serial prints will take 1/11520 seconds per byte.

---

Serial.print("");

What does that do?

---

I count 14 bytes here:

  Serial.print(dataOut);  // 5 bytes, say
  Serial.print("");       // zero bytes, lol
  Serial.print(" ");      // one byte
  Serial.println(val);    // 5 bytes + cr/lf = 7 bytes
  Serial.print(" ");      // 1 byte

Multiply 1/11520 (0.0000868) by 14 and you get 1215 µs.

---

Now add in your delays:

  delay(2);  // 2000 µs

---

And this:

 for (int x = 0; x < 10; x++) {
    ...
    delayMicroseconds(1); //Tclk/2
    ...
    delayMicroseconds(1); //Tdo valid, like Tclk/2
  }

Another 20 µs.

---

  val = analogRead(analogPin);   // 104 µs
  ...
  delayMicroseconds(1); // 1 µs

---

Total:

1215 + 2000 + 20 + 104 + 1 = 3340 µs

Inverse:

1 / 0.003340 = 299

---

So yes, I would expect around 299 iterations per second. That isn't counting the time for the other code to execute.

---

Suggestions

• Get rid of the serial prints
• Get rid of delay(2)