ESP8266 Community Forum

- Mon May 11, 2020 3:26 pm #87044 Hello all,

I'm new to the ESP8266 and working on a battery-powered ESP8266 device and having some issues with reliability of the device reporting after deep sleep. The device is set to deep sleep for 10 minutes, report the sensor reading over MQTT then go back to sleep:



I've highlighted periods where it misses a report.

Here is the circuit:



Here is the sketch:

Code: Select all/*
 * ESP-12F with DHT22 (battery-powered)
 * 
 * MQTT Temperature and Humidity Sensor
 *
 * Designed for integration with HomeAssistant
 *
 */

#include <DHTesp.h>
#include <ESP8266WiFi.h>
#include <PubSubClient.h>

WiFiClient espClient;
PubSubClient client(espClient);

DHTesp dht;

// Serial debug output
#define debug false

// Device details
#define device "test" // will prefix later parameters
#define dhtDataPin 14 // GPIO14
#define dhtPowerPin 12 // GPIO12

// WiFi credentials.
#define wifi_hostname device "-sensor"
#define wifi_ssid "SSID"
#define wifi_password "PASSPHRASE"
IPAddress ip(0,0,0,0);
IPAddress gateway(0,0,0,0);
IPAddress subnet(255,255,255,0);

// Reporting
#define polling_m 10 // every X minutes
#define polling_s polling_m * 60
#define polling_ms polling_s * 1000
#define polling_us polling_ms * 1000
#define mqtt_server "IP.AD.DRE.SS"
#define humidity_topic device "/humidity"
#define temperature_topic device "/temperature"

void setup() {

  // switch off WiFi until we need it
  WiFi.mode(WIFI_OFF);
  WiFi.forceSleepBegin();
  delay(1); 

  // switch on the DHT22 sensor
  pinMode(dhtPowerPin,OUTPUT);
  digitalWrite(dhtPowerPin, HIGH);
 
  dht.setup(dhtDataPin, DHTesp::DHT22); // Connect DHT sensor
 
  if (debug) {
    Serial.begin(115200);
    while (!Serial) {}
    Serial.print("Connecting to ");
    Serial.println(wifi_ssid);
  }
 
  WiFi.forceSleepWake();
  delay(1);

  WiFi.persistent(false);

  // Bring up the WiFi connection
  WiFi.mode(WIFI_STA);

  // Static IP assignment
  WiFi.config(ip,gateway,subnet);

  WiFi.hostname(wifi_hostname);

  WiFi.begin(wifi_ssid, wifi_password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(100);
    if (debug) Serial.print(".");
  }

  float humidity = dht.getHumidity();
  float temperature = dht.getTemperature();

  if (debug) {
    Serial.println("");
    Serial.println("WiFi connected");
    Serial.println("IP address: ");
    Serial.println(WiFi.localIP());
    Serial.println();
    Serial.print("Temperature (C): ");
    Serial.println(temperature);
    Serial.print("Humidity (%): ");
    Serial.println(humidity);       
  }

  client.setServer(mqtt_server, 1883);

  if (!client.connected()) {
    if (debug) Serial.print("Attempting MQTT connection...");
    if (client.connect("ESP8266Client")) {
      if (debug) Serial.println("connected");
    } else {
        if (debug) {
          Serial.print("failed, rc=");
          Serial.print(client.state());
          Serial.println(" trying again in 2 seconds");
        }
      // Wait 2 seconds before retrying
      delay(2000);
    }
  }
 
  client.publish(temperature_topic, String(temperature).c_str(), true);
  client.publish(humidity_topic, String(humidity).c_str(), true);
  client.disconnect(); // make sure the message is sent

  if (debug) Serial.println("Going to sleep");

  // switch off DHT22 sensor
  digitalWrite(dhtPowerPin, LOW);

  ESP.deepSleep(polling_us, WAKE_RF_DISABLED ); // in uS
   
} // end setup

void loop() {
} // end loop


So my questions are:

1. Is this expected? I have read about unreliability of the chip/WiFi in general so should I be happy with the above results?
2. I'm not pulling RST HIGH as I saw there is a 12K internal PULLUP resistor. Should I also add a 10K PULLUP?

Any other feedback on getting a long-lasting low powered device working very welcome.

Thanks,

A

Last edited by amadeuspzs on Wed May 27, 2020 7:46 am, edited 1 time in total.

- Tue May 12, 2020 5:01 am #87054 the wake-up times are not nearly precise but usually they are reliable.
More likely it is due to collisions on wifi and poor error recovery in libraries.

- Tue May 12, 2020 7:32 am #87064 The fact that it is missing a report but they are still at 10 minute boundaries would indicate that the wake up is happening OK but a report is occasionally not getting made.

Internal pull up on reset is OK.

The voltage regulator you are using is definitely marginal. This device can only supply 250mA max. The ESP can need up to 350mA for short periods during some wifi operations. Your reservoir capacitors would not supply the extra current during these peaks. This might be contributing to unreliability in reporting. I would replace the regulator with something like an XC6203E which can supply the current demands.

- Tue May 12, 2020 8:01 am #87065 Thanks for your replies - and good spot on the regulator.

I have two other devices running off mains power and still see missing reports, so I think it may be an error handling issue. I have good WiFi connection error handling so I'm not worried about that.

The issue may be from the following snippet:

Code: Select allclient.publish(temperature_topic, String(temperature).c_str(), true);
client.publish(humidity_topic, String(humidity).c_str(), true);
client.disconnect(); // make sure the message is sent

I'm not actually checking the return values of the `.publish` functions. I may want to let it fail silently rather than retry N times as that will drain battery life further, and I don't mind if I miss, say, 10 minutes.

I'll try some more debugging on the mains-powered versions which also shop skips.

Thanks,

A