analogRead forces WiFi to disconnect

[renno-bih]

Hello,
I'm trying to make sound detection with my esp8266 and this is part of code I'm using:

sample = analogRead(NOISE_SENSOR);
if (sample < 1024) // toss out spurious readings
{
if (sample > signalMax)
{
signalMax = sample; // save just the max levels
}
else if (sample < signalMin)
{
signalMin = sample; // save just the min levels
}
}

Every 10-20 seconds WiFi disconnects. When I use delay(3); after analogRead it works without disconnecting WiFi but with this delay I don't get enough samples.
Any idea what I'm doing wrong?

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[chaeplin]

I am using EmonLib(Electricity monitoring using analog CT sensor) with esp8266 without problem.
https://github.com/openenergymonitor/EmonLib/blob/master/EmonLib.cpp#L175-L209

Can you share your sketch ?

[supersjimmie]

Have you tried using yield() instead of delay(3)?
Might be that you have a too tight (while?) loop or something, but that is hard to see without your complete code.

[renno-bih]

Here is code:

const int sampleWindow = 50; // Sample window width in mS (50 mS = 20Hz)
unsigned int sample;

WiFiManager wifi;

void setup() 
{
  //analogReference(EXTERNAL);
  Serial.begin(115200);
  if (!wifi.autoConnect("esp_test")){
    Serial.println("not connected");
  }
}

 void loop() 
{
while (WiFi.status() != WL_CONNECTED) {

    Serial.println("notready");

  }

   unsigned long startMillis= millis();  // Start of sample window
   unsigned int peakToPeak = 0;   // peak-to-peak level
   unsigned int signalMax = 0;
   unsigned int signalMin = 1024;

   // collect data for 50 mS
   while (millis() - startMillis < sampleWindow)
   {
      sample = analogRead(A0);
      delay(3);
      if (sample < 1024)  // toss out spurious readings
      {
         if (sample > signalMax)
         {
            signalMax = sample;  // save just the max levels
         }
         else if (sample < signalMin)
         {
            signalMin = sample;  // save just the min levels
         }
      }
   }
   peakToPeak = signalMax - signalMin;  // max - min = peak-peak amplitude
   double volts = (peakToPeak * 3.3) / 1024;  // convert to volts
   Serial.println(peakToPeak);
}

Yep, I tried using yield();after analogRead but without success.

[chaeplin]

@renno-bih I ran a test without delay(3) at least 10 mins, no problem at all.

[krzychb]

@renno-bih,

This is the clue I have been looking for 😄

I observed similar issue of Wi-Fi connection being dropped after intensive analogRead(A0) when calibrating light sensor for max and min light intensity. I suspected my code doing something wired that should be tracked down before it does something worse.

I have checked your code and I observe this issue every 5 – 6s using your sketch after slight modification to see seconds when the connection is lost. There are no issues at all if delay(3) is but back.
analogRead-vs-WiFi.ino.txt

For testing I have been using: Arduino IDE 1.6.7 with core 2.0.0 and flash settings below:

@chaeplin

You are our hope of using core version, flash settings or something else that does not produce this issue. Could you share your settings and thoughts?

BTW – I enjoy your huge number of projects with esp, nRF24, Arduino, ATtiny85, etc. Watching pictures of variety of your porotypes is fun 👍

Krzysztof

[chaeplin]

@krzychb I use git version of esp8266/Arduino with Arduino IDE 1.6.7, 80M/4M(1M)/ESP-12.
edit: + not using WiFiManager. STA mode.

[renno-bih]

@chaeplin WiFi Manager library is used just for configuring SSID and Pass for the first time. It doesn't make any effect on this.

I tried running the same code in AP mode and I have problems there too.
When using delay(3) everything works fine but if I run it without delay I cannot see SSID of my ESP on my smartphone. Looks like it conflicts with AP mode too.

[chaeplin]

@renno-bih I have tested again and have no reconnect.
But when I covered antenna area, reconnect occurred.
I think disconnect is caused by weak wifi signal.

My AP : dlink 868L/dd-wrt, B/G/N, Beacon 100ms, DTIM 1

  Serial.print((millis()-millisConnected)/1000);
  Serial.print(" - mode : ");
  const char* phymodes[] = { "", "B", "G", "N" };
  Serial.print(phymodes[(int) wifi_get_phy_mode()]);
  Serial.print(" - rssi : ");
  Serial.print(WiFi.RSSI());
  Serial.print(" - peakToPeak : ");
  Serial.println(peakToPeak);

41 - mode : N - rssi : -67 - peakToPeak : 1
41 - mode : N - rssi : -67 - peakToPeak : 1
not connected...........
0 - mode : N - rssi : -71 - peakToPeak : 1
0 - mode : N - rssi : -71 - peakToPeak : 1

[renno-bih]

It doesn't make sense in my case because my smartphone is just few centimeters from ESP.

[chaeplin]

@renno-bih Which version of IDE, esp8266 core and OS do you use ? I will try.

[renno-bih]

IDE, 1.6.6,
esp8266 core: 1.6.5-947-g39819f0
OS: ubuntu 14.04

Thank for helping me :)

[chaeplin]

I think wifi mode 11B is the root.

tested with
WiFi.setPhyMode(WIFI_PHY_MODE_11B); ----> reconnect
WiFi.setPhyMode(WIFI_PHY_MODE_11G); ----> some(?)
WiFi.setPhyMode(WIFI_PHY_MODE_11N); ---> some(?)

https://gist.github.com/chaeplin/8ff93aedb75266d644d2

[Links2004]

the ADC is also used from the WiFi part to measure the internal voltage to adjust output power,
may this get problematical when the ADC is in use for too much time in the sketch.

[krzychb]

@renno-bih,
Is it the option to add delay after taking all the samples inside 50ms window, instead of after every individual sample? After doing so I do not see reconnects. Basing on the above comment by Links2004 I believe we should periodically insert some delay into stream of continuous analogRead(A0).
analogRead-vs-WiFi.ino.txt

645 - mode : N - rssi : -75 - peakToPeak : 3 - reconected : 0
645 - mode : N - rssi : -75 - peakToPeak : 3 - reconected : 0
645 - mode : N - rssi : -74 - peakToPeak : 0 - reconected : 0
645 - mode : N - rssi : -74 - peakToPeak : 3 - reconected : 0
646 - mode : N - rssi : -74 - peakToPeak : 0 - reconected : 0
646 - mode : N - rssi : -74 - peakToPeak : 1 - reconected : 0
646 - mode : N - rssi : -74 - peakToPeak : 6 - reconected : 0
646 - mode : N - rssi : -74 - peakToPeak : 0 - reconected : 0
646 - mode : N - rssi : -73 - peakToPeak : 1 - reconected : 0
646 - mode : N - rssi : -73 - peakToPeak : 6 - reconected : 0
646 - mode : N - rssi : -73 - peakToPeak : 0 - reconected : 0

@chaeplin,
I did the testing with Wi-Fi B, G and N modes for code without delay and each time see the reconnects. I made testing with core 2.1.0-rc2. Still need to check the GitHub version.

Krzysztof

[renno-bih]

@chaeplin Nice found.
@krzychb True, I don't see reconnects if I'm taking 50ms samples and make delay. But I see other problems. I'm using Websockets and I notice lot of lag when exchanging some data and random disconnects from my websocket server.
This device should run stable without making any delay in communication and without random resets. Hmmm, does it mean that I should forget using analog pin for noise measurements. Hmmm