Problem on change the sampling rate of the sensor

Projects Programming
1

hello,I want to change the sampling rate of the sensor, because the input of the sensor is analog, and the sampling rate can be modified by the size of the delay, but how do I need to change it in the way that the ADC does? What is the difference and relationship between the two? Thanks!

2

Which sensor ?

Please post your sketch, using code tags when you do

3

Quick postings just slow things down through asking back.

What exact type of microcontroller do you use?

The sensor has an output

What does this mean

?

a function-call to function delay()?

What do you mean by asking

totally unclear.
Do you want to now how long it takes for the ADC to sample the voltage and how to change this sampling-time inside the ADC?

Or do you want your code to measure with a different interval?

If you would descibe in detail what you want to do and give a project overview taking 10 minutes time to write down such a description will save you minimum 100 minutes
through getting the asnwer with the next post.

4

Avoid delay()

Try this... sampletime is in milliseconds made a light change... now microseconds.

unsigned long timer, sampletime = 250000UL; // change sampletime

void setup() {
  Serial.begin(115200);
}

void loop() {
  if (micros() - timer > sampletime) { // wait for sampletime
    timer = micros(); // reset timer
    sample(); // call sample function
  }
}

void sample() {
  Serial.print(1); // take a sample
}
5

I'm sorry for not describing my problem clearly. Here are the details:
I'm testing a GSR sensor that collects skin electricity, which collects signals through an analog input A0.
The sample code is as follows：

`const int LED=13;
const int GSR=A0;
int threshold=0;
int sensorValue;

void setup(){
    long sum=0;
    Serial.begin(9600);
    pinMode(LED,OUTPUT);
    digitalWrite(LED,LOW);
    delay(1000);

    for(int i=0;i<500;i++)
        {
            sensorValue=analogRead(GSR);
            sum += sensorValue;
            delay(5);
        }
    threshold = sum/500;
    Serial.print("threshold =");
    Serial.println(threshold);
}

void loop(){
    int temp;
    sensorValue=analogRead(GSR);
    Serial.print("sensorValue=");
    Serial.println(sensorValue);
    temp = threshold - sensorValue;
    if(abs(temp)>60)
    {
        sensorValue=analogRead(GSR);
        temp = threshold - sensorValue;
        if(abs(temp)>60){
            digitalWrite(LED,HIGH);
            Serial.println("Emotion Changes Detected!");
            delay(3000);
            digitalWrite(LED,LOW);
            delay(1000);
        }
    }
}`

I'm using an Arduino uno r3 board to collect data, and since the default sampling rate of the sensor is only 50Hz, I want to try to modify the sampling rate to 128hz using an ADC.I've tried using timed sampling, maybe that's okay too?

6

Thanks! I will try it.

7 
const int GSR=A0;
int sensorValue;

      
unsigned long timer, sampletime = 7812; // change sampletime
    
void setup(){
    Serial.begin(115200);
}

void loop(){
  if (micros() - timer > sampletime) { // wait for sampletime
    timer = micros(); // reset timer
    recordTime();//打印采样时间
    sensorValue = analogRead(GSR);
    Serial.print(GsensorValue); //皮肤电导
}
void recordTime() {
  unsigned long timestamp = micros(); // 获取当前时间戳（微秒）
  Serial.print("Timestamp: "); // 打印标签
  Serial.print(timestamp);  // 打印时间戳（秒，保留四位小数）
  Serial.print('\t');
}

I used the timed sampling method to control the sampling output of the ADC, which seems to be feasible. If I want to adjust the sampling rate through clock control, may I just modify the analogRead() function to control the ADC?

8

If I understand your question, adjust sampletime

9

You seem to have a different understanding or at least assumings how this works.

You are still very foggy in your descriptions. What do you mean by "clock control"?
which clock? The CPU-Clock? The chrystal that generates the clock-signal for the CPU?

This would be the most complicated way to change the sample-time.

Modifying the analogRead() is possible but is a real bad idea. You would change a part of the core-files which would them make incompatible to the standard.

Let the analogRead() do its thing as fast as possible.
You should learn about non-blocking timing to get a different sample-rate

10

Thanks for your reply, it helps me a lot!