Problems using wifi with analog

[michael899]

Hi,
I am using ESP32-WROOM-32D.
So i've been trying to do some data collection with my Microphone and send it over the MQTT.
I noticed that when I enter the specific function (code below) I get alot of noises (Used a scope to check ).
So i connected the scope to the analog I(GPIO 39).
I found out, that when I comment the "setup_wifi()" (Line 30) function, the noises stop. when i uncomment it, i get alot of noises from the GPIO39.
the thing is, that the noises are very high peaks that change the whole values of the fft (+-10dB, instead of +-0.5dB) so i really need to fix it.

I attached a photo of the noises that I measure with the O-Scope

I would really appreciate your help on how to reduce the noises and make my sampling more accurate.

Code: [Select all] [Expand/Collapse]

1. #include <WiFi.h>
2. #include <Wire.h>
3. #include "arduinoFFT.h"
4. #include "Math.h"
5.  
6.  
7. const uint16_t samples = 4096; //This value MUST ALWAYS be a power of 2
8. unsigned int sampling_period_us;
9. const double samplingFrequency = 2500;
10. double vReal[4096];
11. double vImag[4096];
12. arduinoFFT FFT = arduinoFFT(vReal, vImag, samples, samplingFrequency); /* Create FFT object */
13. int newTime;
14.  
15.  
16. char machine[] = "FVT-PCB-001";
17. char TFS_TOPIC[50] ; char Voice_TOPIC[50]; char Request_TOPIC[50];
18.  
19.  
20. const char* ssid = "ABCD";
21. const char* password = "12345678";
22.  
23.  
24. WiFiClient espClient;
25.  
26.  
27. void setup() {
28.   // put your setup code here, to run once:
29.   Serial.begin(115200);
30.   setup_wifi();
31.   //pinMode(4, OUTPUT);
32.   pinMode(36, INPUT);
33.   digitalWrite(4, HIGH);
34.   sampling_period_us = round(100000*(1.0/samplingFrequency));
35. }
36.  
37. void loop() {
38.   double dB[samples/2];
39.   int x;
40.   // put your main code here, to run repeatedly
41.      for (int i=1;i<samples;i++)
42.      {
43.       newTime = micros();
44.      vReal[i] = analogRead(39)*3.3/4095;
45.      vImag[i] = 0;
46.      while(micros() < (newTime + sampling_period_us));
47.      }
48.      //for (int i = 1;i<samples;i++)
49.      //{
50.      // Serial.println(vReal[i]);
51.      //}
52.       FFT.DCRemoval();
53.       FFT.Windowing(FFT_WIN_TYP_HANN, FFT_FORWARD);
54.       FFT.Compute(FFT_FORWARD); /* Compute FFT */
55.       FFT.ComplexToMagnitude(); /* Compute magnitudes */
56.      delay(100);
57.    for (int i = 232 ;i<235;i++) // 1KHz
58.   {
59.     //dB[i] = 20*log10((vReal[i]*Cal_Val)/(EEPROM.read(Sensor)*0.001));
60.     dB[i] = 20*log10((vReal[i]*500)/(50*0.01));
61.     x = int(i*1000/234);
62.     Serial.println();
63.     Serial.print("Freq:   ");
64.     Serial.println(x);
65.     Serial.print("dB:     ");
66.     Serial.println(dB[i]);
67.     //doc["value"][String(x)] = dB[i];
68.   }
69.   delay(1000);
70.  
71.  
72. }
73.  
74. void setup_wifi()
75. {
76.   delay(10);
77.   // We start by connecting to a WiFi network
78.   WiFi.begin(ssid, password);
79.   while (WiFi.status() != WL_CONNECTED)
80.   {
81.     delay(500);
82.     Serial.println("Problem in wifi");
83.   }
84.  
85. }
86.  

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[ESP_Sprite]

What's your schematic like? Could it be that your amp or your wires are picking up radiated noise from the antenna or power supply?

[akhilchandran]

Dear friend,
I too face noise issue when connecting with wifi. I recently developed a DAQ and I noticed some points.
1. Noise is not due to any kind of interference, but due to the fluctuations of Vcc due to self consumption.
2. If you check the 3.3V pin and 5V pin, you can see these noises are there too. These voltages keep on fluctuate.
3. Putting a capacitor on 5V pin can stabilise these noises to some extent
4. Use of an ADC will be a good option.