ESP-Now Remote Sensor 1 Example

#include <ESP8266WiFi.h>
#include <Wire.h>

extern "C" {
#include <espnow.h>
}

//Thermistor related:

/* Here we have a few constants that make editing the code easier. I will go
   through them one by one.

   A reading from the ADC might give one value at one sample and then a little
   different the next time around. To eliminate noisy readings, we can sample
   the ADC pin a few times and then average the samples to get something more
   solid. This constant is utilized in the readThermistor function.
   */
const int    SAMPLE_NUMBER      = 10;

/* In order to use the Beta equation, we must know our other resistor
   within our resistor divider. If you are using something with large tolerance,
   like at 5% or even 1%, measure it and place your result here in ohms. */
const double BALANCE_RESISTOR   = 9970.0;

// This helps calculate the thermistor's resistance (check article for details).
const double MAX_ADC            = 1023.0;

/* This is thermistor dependent and it should be in the datasheet, or refer to the
   article for how to calculate it using the Beta equation.
   I had to do this, but I would try to get a thermistor with a known
   beta if you want to avoid empirical calculations. */
const double BETA               = 3950.0;

/* This is also needed for the conversion equation as "typical" room temperature
   is needed as an input. */
const double ROOM_TEMP          = 298.15;   // room temperature in Kelvin

/* Thermistors will have a typical resistance at room temperature so write this
   down here. Again, needed for conversion equations. */
const double RESISTOR_ROOM_TEMP = 10000.0;

//===============================================================================
//  Variables
//===============================================================================
// Here is where we will save the current temperature
double currentTemperature = 0;

//===============================================================================
//  Pin Declarations
//===============================================================================
//Inputs:
int thermistorPin = 0;  // Where the ADC samples the resistor divider's output

// this is the MAC Address of the remote ESP server which receives these sensor readings
uint8_t remoteMac[] = {0x86, 0xF3, 0xEB, 0X62, 0x71, 0xEC};

#define WIFI_CHANNEL 1
#define SLEEP_SECS 5  // 15 minutes
#define SLEEP_TIME 36e8 //6e7 // has to be number of seconds * 1000 * 1000 i.e. 10s is 10 * 1000 * 1000 = 10000000 or 1e7 ( 1 + 7 zeros) for testing 1e7, 6e7 = 60s & 36e8 is 1 hour
#define SEND_TIMEOUT 245  // 245 millis seconds timeout

unsigned long entry;

// keep in sync with ESP_NOW sensor struct
struct SensorData {
    String id; //Sensor Name
    int fieldT; // ThingSpeak Field Temperature
    int fieldH; // ThingSpeak Field Humidity
    float temp; // Temperature Variable
    int hum; // Humidity Variable
} sD;

volatile boolean callbackCalled;

unsigned long entry1 = millis();

void setup() {
  Serial.begin(115200);
  sensor.begin();
  Serial.println();
  Serial.println();
  Serial.println("ESP_Now Controller");
  Serial.println();
  WiFi.mode(WIFI_STA);
  WiFi.disconnect();

  Serial.printf("This mac: %s, ", WiFi.macAddress().c_str());
  Serial.printf("target mac: ");
  char macString[50] = {0};
    sprintf(macString,"%02X:%02X:%02X:%02X:%02X:%02X", remoteMac[0], remoteMac[1], remoteMac[2], remoteMac[3], remoteMac[4], remoteMac[5]);
    Serial.print(macString);
  Serial.printf(", on channel: %i\n", WIFI_CHANNEL);


  if (esp_now_init() != 0) {
    Serial.println("*** ESP_Now init failed");
    gotoSleep();
  }
  esp_now_set_self_role(ESP_NOW_ROLE_CONTROLLER);

  unsigned long entry2 = millis();
  esp_now_add_peer(remoteMac, ESP_NOW_ROLE_SLAVE, WIFI_CHANNEL, NULL, 0);

  unsigned long entry3 = millis();

  esp_now_register_send_cb([](uint8_t* mac, uint8_t sendStatus) {
    Serial.println();
    Serial.printf("send_cb, send done, status = %i\n", sendStatus);
    callbackCalled = true;
  });

  unsigned long entry4 = millis();

  callbackCalled = false;

}

void loop() {
  currentTemperature = readThermistor();
  sD.id = "H";
  sD.fieldT = 4;
  sD.temp = currentTemperature;
  u8 bs[sizeof(sD)];
  memcpy(bs, &sD, sizeof(sD));
  unsigned long entry = millis();
  esp_now_send(NULL, bs, sizeof(sD)); // NULL means send to all peers

  Serial.print("Overall Time: ");
  Serial.println(millis() - entry1);
  Serial.print(sD.id); Serial.printf(" Temp = %0.2f", sD.temp); Serial.print("\u2103");
  ESP.deepSleep(SLEEP_TIME, WAKE_RF_DEFAULT);
  ESP.restart();
}

void gotoSleep() {
  // add some randomness to avoid collisions with multiple devices
  int sleepSecs = SLEEP_SECS;// + ((uint8_t)RANDOM_REG32/2);
  Serial.printf("Up for %i ms, going to sleep for %i secs...\n", millis(), sleepSecs);
  ESP.deepSleep(sleepSecs * 1000000, RF_NO_CAL);
}

double readThermistor()
{
  // variables that live in this function
  double rThermistor = 0;            // Holds thermistor resistance value
  double tKelvin     = 0;            // Holds calculated temperature
  double tCelsius    = 0;            // Hold temperature in celsius
  double adcAverage  = 0;            // Holds the average voltage measurement
  int    adcSamples[SAMPLE_NUMBER];  // Array to hold each voltage measurement

  /* Calculate thermistor's average resistance:
     As mentioned in the top of the code, we will sample the ADC pin a few times
     to get a bunch of samples. A slight delay is added to properly have the
     analogRead function sample properly */

  for (int i = 0; i < SAMPLE_NUMBER; i++)
  {
    adcSamples[i] = analogRead(thermistorPin);  // read from pin and store
    delay(1);        // wait 10 milliseconds
  }

  /* Then, we will simply average all of those samples up for a "stiffer"
     measurement. */
  for (int i = 0; i < SAMPLE_NUMBER; i++)
  {
    adcAverage += adcSamples[i];      // add all samples up . . .
  }
  adcAverage /= SAMPLE_NUMBER;        // . . . average it w/ divide

  /* Here we calculate the thermistor’s resistance using the equation
     discussed in the article. */
  rThermistor = BALANCE_RESISTOR * ( (MAX_ADC / adcAverage) - 1);

  /* Here is where the Beta equation is used, but it is different
     from what the article describes. Don't worry! It has been rearranged
     algebraically to give a "better" looking formula. I encourage you
     to try to manipulate the equation from the article yourself to get
     better at algebra. And if not, just use what is shown here and take it
     for granted or input the formula directly from the article, exactly
     as it is shown. Either way will work! */
  tKelvin = (BETA * ROOM_TEMP) /
            (BETA + (ROOM_TEMP * log(rThermistor / RESISTOR_ROOM_TEMP)));

  /* I will use the units of Celsius to indicate temperature. I did this
     just so I can see the typical room temperature, which is 25 degrees
     Celsius, when I first try the program out. I prefer Fahrenheit, but
     I leave it up to you to either change this function, or create
     another function which converts between the two units. */
  tCelsius = tKelvin - 273.15;  // convert kelvin to celsius

  tCelsius = round(tCelsius*10)/10.0;

  return tCelsius;    // Return the temperature in Celsius
}