ESP8266 Community Forum

Posted: **Mon Jul 06, 2015 1:22 am**

Here is some debug data from a little power monitor I created. It reads from the ADC pin and calculates power used with the help of a ACS712 current sensor.

But I have noticed that the following occurs

Connect TO WIFI
After 3 seconds it disconnects
After about 6 seconds it says there is no access point

Then next time it comes to upload I reconnect (since it is not connected) and the same thing happens time and time again.

Connecting to CROWE
......
WiFi connected
IP address:
192.168.2.128
Interval=1, WiFi.status=WL_CONNECTED=3
Interval=2, WiFi.status=WL_CONNECTED=3
Interval=3, WiFi.status=WL_CONNECTED=3
Interval=4, WiFi.status=WL_CONNECTED=3
Interval=5, WiFi.status=WL_DISCONNECTED=6
Interval=6, WiFi.status=WL_DISCONNECTED=6
Interval=7, WiFi.status=WL_DISCONNECTED=6
Interval=8, WiFi.status=WL_DISCONNECTED=6
Interval=9, WiFi.status=WL_DISCONNECTED=6
Interval=10, WiFi.status=WL_DISCONNECTED=6
Interval=11, WiFi.status=WL_DISCONNECTED=6
Interval=12, WiFi.status=WL_NO_SSID_AVAIL=1
Interval=13, WiFi.status=WL_NO_SSID_AVAIL=1
Interval=14, WiFi.status=WL_NO_SSID_AVAIL=1
Interval=15, WiFi.status=WL_NO_SSID_AVAIL=1
Interval=16, WiFi.status=WL_NO_SSID_AVAIL=1
Interval=17, WiFi.status=WL_NO_SSID_AVAIL=1
Interval=18, WiFi.status=WL_NO_SSID_AVAIL=1

The code is very simple as I have removed other stuff except WIFI

Code: Select all

#include <ESP8266WiFi.h>

const char* ssid     = "CROWE";
const char* password = "abcd";

const char* host = "192.168.2.122";

String Statuses[] =  { "WL_IDLE_STATUS=0", "WL_NO_SSID_AVAIL=1", "WL_SCAN_COMPLETED=2", "WL_CONNECTED=3", "WL_CONNECT_FAILED=4", "WL_CONNECTION_LOST=5", "WL_DISCONNECTED=6"};
unsigned long lastMillis = 0;
unsigned long lastMillis2 = 0;
int IntervalInSeconds = 1;
int Errors = 0;
int min = 1024;
int max = -1024;
int samples = 0;
void setup() {

  Serial.begin(115200);
  Serial.println("ESP8266 Power Monitor");

  WiFi.mode(WIFI_STA);
  WiFi.disconnect();

  Connect();
}

void Connect()
{
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  int Attempt = 0;
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Attempt++;
    Serial.print(".");
    if (Attempt == 50)
    {
      Serial.println();
      Serial.println("Could not connect to WIFI");
      return;
    }
  }

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void loop()
{
  yield() ; // Allow WIFI to do stuff

  unsigned long CurrentMillis = millis();
  if (CurrentMillis - lastMillis2 > 3)
  {
    lastMillis2 = CurrentMillis;

    double sensorValue = 0;
    for (int reading = 0; reading < 5; reading++)
    {
      sensorValue += analogRead(A0);
    }
    sensorValue /= 5;
    if ((int)sensorValue < min)
      min = (int)sensorValue;
    if ((int)sensorValue > max)
      max = (int)sensorValue;
    samples++;
  }

  if (CurrentMillis - lastMillis > 900)
  {
    lastMillis = CurrentMillis;

    Serial.print("Interval=");
    Serial.print(IntervalInSeconds);
    Serial.print(", WiFi.status=");
    Serial.print(Statuses[WiFi.status()]);

    if (IntervalInSeconds >= 60)
    {
      IntervalInSeconds = 1;

      Serial.print("connecting to ");
      Serial.println(host);

      if (WiFi.status() != WL_CONNECTED)
        Connect();

      if (WiFi.status() == WL_CONNECTED)
      {
        // Use WiFiClient class to create TCP connections
        WiFiClient client;
        const int httpPort = 8080;
        if (!client.connect(host, httpPort)) {
          Serial.println("connection failed");
          return;
        }

        // We now create a URI for the request
        String url = "/Power/?Watts=";
        url += "SOMENUMBER";
        url += "&DeviceID=HomeTheatre";

        Serial.print("Requesting URL: ");
        Serial.println(url);

        // This will send the request to the server
        client.print(String("GET ") + url + " HTTP/1.1\r\n" +
                     "Host: " + host + "\r\n" +
                     "Connection: close\r\n\r\n");
        delay(50);

        // Read all the lines of the reply from server and print them to Serial
        while (client.available()) {
          String line = client.readStringUntil('\r');
          Serial.print(line);
        }
        Serial.println();
      }
      else
      {
        Serial.print("Error Not Connected To WIFI, Error Count: ");
        Serial.println(++Errors);
      }
    }
    else
      Serial.println();

    IntervalInSeconds = IntervalInSeconds + 1;
    min = 1024;
    max = -1024;
    samples = 0;
  }
}

Now I have found two things:

1) The analogRead() is buggy in the current release of the Arduino IDE and I have modified the code for analogRead as per the discussion at the following:

https://github.com/esp8266/Arduino/issues/338

The code I changed it to was this

core_esp8266_wiring_analog.c in the folder C:\Users\ccrowe.AP\AppData\Roaming\Arduino15\packages\esp8266\hardware\esp8266\1.6.4-673-g8cd3697\cores\esp8266

Code: Select all

extern int __analogRead(uint8_t pin) {
   if (pin == 17){
      return 0xffff & system_adc_read();
   }
   return digitalRead(pin) * 1023;
}

This code change fixed the issue with reading erroneous values from the ADC.

But if I comment out the analogRead() in my script the wifi does not disconnect, it stays connected.

So either there is a problem with the system_adc_read() function or something else is going on....

Chris

Posted: **Tue Jul 07, 2015 6:36 pm**

you need to disconnect wifi for stable adc reading and you can reconnect after reading. its chip related not arduino ide

Posted: **Tue Jul 07, 2015 8:13 pm**

Is this a limitation of the esp8266 chip? or the firmware on the chip?

If so it sort of makes esp8266 a bit limited for a lot of cases where one would want to use it.

Are there any other issues like this with the esp8266?

Would using a separate ADC chip over SPI work more reliably?

Chris

Posted: **Tue Jul 07, 2015 8:58 pm**

If you wish to hook up external ADC, yes there are SPI ones such as MCP3008, but you can also use I2C ones such as MCP3021 which would be even more easier, and those ones are really small SOT-23.

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