@Reza I implemented your sketch, tried to start/stop(up to a few hours) the gateway(serial gateway) and the controller(domoticz on orangepi pc) to see if the logs help in some way. Nothing, it works.
It should be logged until the freeze occurs.

@Reza
there are two problems with MQ-2 sensors :
1 the sketch, at the bottom, uses log instead of log10
2 are you sure that RL_VALUE is 5 (kOhm) in your MQ-2 board? In my is 1, the one labeled 102 in the pic.

Regards

1 look at the last line of the sketch:

  return (pow(10, ( ((log(rs_ro_ratio) - pcurve[1]) / pcurve[2]) + pcurve[0])));
}``

change to:

  return (pow(10, ( ((log10(rs_ro_ratio) - pcurve[1]) / pcurve[2]) + pcurve[0])));
}``

2 RL_VALUE in your MQ2 board should be 1 (kohm), R2 in the schematic.

yes, R2 is 1k. Change RL_VALUE from 5 to 1.

I suggest you use the MQ-2 sensor library https://github.com/xerlay11/MQ-2-sensor-library and obviously change log and RL_VALUE.
Regards

Which MySensors library are you using?
With 2.0 i had the sleep issue solved (for now) with MY_PARENT_NODE_ID and MY_PARENT_NODE_IS_STATIC(as suggested by tekka).

@AWI Thanks for the hint.
I thought this wasn't a "issue" but just a "really annoying thing".
However i run domoticz on a Orange PI PC with WiringOP support and i can't find precompiled images.

It should be enough to read ppm from the sensor.

@konbaasiang nice, good to know.
I am having problems with SPI interface.
For example i have a 2.4" TFT+XPT2046 touch controller+SD card reader( all on SPI), after many tests i found out that sometimes, reading from XPT2046 SPI, wavgat add 0x1000h which is impossible since the xpt2046 controller has a 12 bits adc. TFT and card reader are Ok instead.
With genuine arduino all work as expected.
Still testing wavgat+NFR24L01, sometimes works sometimes doesn't.
Regards

@Karolis-Kirna Just a bit late but here it is.

The code:

/*
 * Send Watt and Kwh to gateway
 * using PZEM-004t
 * 26/8/2020  cambiato linea 45, 21-23
 */

/*++++++++++++++  Global Settings   +++++++++++++++++*/
#define SN "PZEM Monitor"
#define SV "0.4"
// Enable and select radio type attached
#define MY_RADIO_NRF24
#define MY_NODE_ID 9
#define MY_PARENT_NODE_ID 11 // from domoticz log
#define MY_PARENT_NODE_IS_STATIC
/*+++++++++++++  Local Settings  ++++++++++++++++++++*/
#define SEND_ONLY_IF_CHANGED  
//#define MY_DEBUG
//#define DEBUG 
//#define TEST // Aggiunge codice di test da levare

#if F_CPU == 8000000L
#define MY_BAUD_RATE 9600
#endif

#include <debugpaolo.h>

#include <SPI.h>
#include <MySensors.h>  
//#include <SoftwareSerial.h> // Arduino IDE <1.6.6
#include <PZEM004T.h>

#define RX_PIN 4  
#define TX_PIN 5 
PZEM004T pzem(RX_PIN,TX_PIN);  // RX pin,TX pin
IPAddress ip(192,168,1,1);

#define CHILD_WATT_ID 0  
#define VOLTAGE_ID  1

unsigned long lastSend=0;
unsigned long SEND_FREQUENCY = 40000; // Minimum time between send (in milliseconds). We don't want to spam the gateway.

MyMessage wattMsg(CHILD_WATT_ID,V_WATT);
MyMessage kWhMsg(CHILD_WATT_ID,V_KWH);
//MyMessage kwhSaveMsg(CHILD_WATT_ID,V_VAR1);
//MyMessage varMsg(CHILD_WATT_ID,V_VAR); // chi lo sa non va in domoticz

double oldKwh=0.0;
double oldwh=0.0;
float oldwatt=0.0;
#ifdef TEST
  double whtest=0.0;
#endif

#ifdef SEND_ONLY_IF_CHANGED
  int kwh_counter;
  #define KWH_COUNTER_MAX 33 //dopo 23 volte(15 min) invia comunque
#endif

MyMessage msgVoltage(VOLTAGE_ID, V_VOLTAGE);
float lastv=0;
#define V_COUNTER_MAX 70
int v_counter=0;

int BATTERY_SENSE_PIN = A3;  // select the input pin for the battery sense point
int oldBatteryPcnt = 0;

#define MAX_BATTERY_CHECK    56  // 56*40 sec = 56 min circa
int battery_check;


#define VREF 1.106
#define RBATT  5.73305  // ((1578+333.4)/333.4)?
#define VFACTOR  RBATT*VREF/1023 //
/*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++   SETUP    +++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
void setup() {
//  begin(incomingMessage);
  analogReference(INTERNAL);
  pzem.setAddress(ip);
  battery_check = MAX_BATTERY_CHECK;
}
/*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++++   Presentation  ++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
void presentation()  {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo(SN, SV);
  present(CHILD_WATT_ID, S_POWER);
  present(VOLTAGE_ID, S_MULTIMETER);
}

/*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++   Loop  +++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
void loop() {

/* +++++++++++++++++++++++++++++++++++++++++++
   ++++    PZEM          section     +++++++++
   +++++++++++++++++++++++++++++++++++++++++++*/  
  float v = pzem.voltage(ip);
  if (v < 0.5) { 
    delay(500);
    // check v twice
    v = pzem.voltage(ip);
    if (v < 0.5 ) v = 0.0;
  }
  DEBUG_PRINT(v);DEBUG_PRINT("V; ");
#ifdef DEBUG  
  float i = pzem.current(ip);
  if(i >= 0.0){ DEBUG_PRINT(i);DEBUG_PRINT("A; "); }
  float VA=v*i;
  if(VA >= 0.0){ DEBUG_PRINT(VA);DEBUG_PRINTLN("VA; "); }
#endif  
/* ---------------------------
 *------- Sezione potenza ----
  ----------------------------*/
  float watt = pzem.power(ip);
  #ifdef TEST
    watt=kwh_counter*2;
  #endif  
  DEBUG_PRINT(watt);DEBUG_PRINT("W ");DEBUG_PRINT(VA);DEBUG_PRINTLN("VA ");
  if (watt <=0 ) {
    DEBUG_PRINT(watt);DEBUG_PRINTLN("W. Sensore NC o assenza rete! ");
    if ( oldwatt>0) {
       watt =0;
       send(wattMsg.set(watt,1));  // Send watt value to gw 
       oldwatt=0.0;
    }
  } 
  else {
   if ( oldwatt==0.0) {
    send(wattMsg.set(watt,1));  // Send watt value to gw 
    DEBUG_PRINT(watt);DEBUG_PRINTLN("Rete ritornata! ");
    oldwatt = watt;
   }
   else {
    DEBUG_PRINT(watt);DEBUG_PRINTLN("W; ");
    float diffwatt=abs(watt-oldwatt);
    if ( diffwatt >= 49.9 ) { // watt in aumento di 50watt
        DEBUG_PRINT("Differenza ");DEBUG_PRINT(diffwatt);DEBUG_PRINTLN("W; ");
        oldwatt = watt;
        send(wattMsg.set(watt,1));  // Send watt value to gw 
    }
    else {
      float perc = 100.0*diffwatt/oldwatt; // oldwatt o watt?
      DEBUG_PRINT("Perc ");DEBUG_PRINT(perc);DEBUG_PRINTLN("% ");
      if ( perc >= 49.9 ) { // variazione del 50%
        DEBUG_PRINT("Percentuale Diff ");DEBUG_PRINT(perc);DEBUG_PRINTLN("%; ");
        oldwatt = watt;
        send(wattMsg.set(watt,1));  // Send watt value to gw 
//        send(varMsg.set(watt,1));  // non va in domoticz
      }
      else {
        if ( (perc >= 15.0) && (diffwatt>=8) ) {
          DEBUG_PRINT("Diff ");DEBUG_PRINT(diffwatt);
          DEBUG_PRINT("Perc ");DEBUG_PRINT(perc);DEBUG_PRINTLN("%; ");
          oldwatt = watt;
          send(wattMsg.set(watt,1));  // Send watt value to gw 
        }
      }
    }
   }
  }
  
  //send(wattMsg.set(watt,1));  // Send watt value to gw 
/* ---------------------------
 *------- Sezione energia ----
  ---------------------------*/
  float wh = pzem.energy(ip);
  #ifdef TEST
    whtest+=10.0;
    wh=whtest;
  #endif
  if(wh >= 0.0){ DEBUG_PRINT(wh);DEBUG_PRINT("Wh; "); }
  else wh = 0.0;
  DEBUG_PRINTLN();
  
#ifdef SEND_ONLY_IF_CHANGED 
  if ( (kwh_counter==0) ||(abs(wh-oldwh) > 187) ) { // 100 wh
#else    
  if ( wh > 0.0 ) { 
#endif    
      double kwh = (double)wh/(double)1000.0;
      send(kWhMsg.set(kwh, 3));  // Send kwh value to gw 
      oldwh=wh;
      #ifdef SEND_ONLY_IF_CHANGED 
      kwh_counter=0;
      #endif      
  }
#ifdef SEND_ONLY_IF_CHANGED 
  DEBUG_PRINT("kwh_counter=");
  kwh_counter++;
  DEBUG_PRINT(kwh_counter);DEBUG_PRINT(" ");
  if (kwh_counter == KWH_COUNTER_MAX ) kwh_counter = 0;
  DEBUG_PRINTLN();
#endif    

/* +++++++++++++++++++++++++++++++++++++++++++
   ++++    Battery check section     +++++++++
   +++++++++++++++++++++++++++++++++++++++++++*/
  if ( battery_check == MAX_BATTERY_CHECK) {
    analogRead(BATTERY_SENSE_PIN); // needed for accuracy
    int sensorValue = analogRead(BATTERY_SENSE_PIN);
    DEBUG_PRINT("A0 Value = ");DEBUG_PRINTLN(sensorValue);
    float batteryV  = sensorValue * VFACTOR;
    // 100% 4.0v 0% 3.3v
    int batteryPcnt = ( batteryV - 3.3) / (4.0 - 3.3) * 100;
    batteryPcnt = (batteryPcnt > 100) ? 100 : batteryPcnt;
    batteryPcnt = (batteryPcnt < 0) ? 0 : batteryPcnt;
    DEBUG_PRINT("Battery Voltage: ");DEBUG_PRINT(batteryV);DEBUG_PRINTLN(" V");
    DEBUG_PRINT("Battery Percent: ");DEBUG_PRINT(batteryPcnt);DEBUG_PRINTLN(" %");
    //if (oldBatteryPcnt != batteryPcnt) {
     sendBatteryLevel(batteryPcnt);
     oldBatteryPcnt = batteryPcnt;
    //}
    battery_check=0;
  } else {
     battery_check++;
     DEBUG_PRINT("Check = ");
     DEBUG_PRINTLN(battery_check);
    }
/* +++++++++++++++++++++++++++++++++++++++++++
   ++++    230 Voltage   section     +++++++++
   +++++++++++++++++++++++++++++++++++++++++++*/  
#ifdef SEND_ONLY_IF_CHANGED 
  float diffv= abs(v-lastv);
  if ( ((v_counter == 0) || ( diffv > 3.50))  ) {
    DEBUG_PRINT("v diff: ");DEBUG_PRINT(diffv);DEBUG_PRINTLN("V ");
    if ( diffv > 3.50 ) v_counter = 0;
    else v_counter++;
    DEBUG_PRINT("v_counter : ");DEBUG_PRINTLN(v_counter);
#endif
    send(msgVoltage.set(v, 1));
    lastv = v;
#ifdef SEND_ONLY_IF_CHANGED 
  } else {
    v_counter++;
    if (v_counter >= V_COUNTER_MAX ) v_counter = 0;
    DEBUG_PRINT("v_counter : ");DEBUG_PRINTLN(v_counter);
  }
#endif
  sleep(SEND_FREQUENCY);
  delay(500); // ???
}

@jaykumar Yes,
i built it a couple of years ago, but it's operative for about three months.
I used :
arduino mini pro 3.3v/8Mhz powered by a 3.7v 14500 Li-Ion battery
NRF24L01
PZEM-004T (modified to work at 3.3v)

It's a simple watt/energy meter that sends data to the controller(domoticz) every 40 secs, the PZEM-004T does most of the work.

@Reza
sorry, I made a mistake. You have to check AOUT.

@Reza
you can't convert 16 bits unsigned integers greater than 32767 into 16 bits signed integers because they're treated as negative numbers according to 2's complement math.
You must check with a multimeter VCC(for supply voltage sanity) and DOUT( for ppm reading) on the sensor board.

I see two lines to be modified:

if (b == 0) { 
    uint16_t valMQ = MQGetGasPercentage(MQRead(MQ_SENSOR_ANALOG_PIN) / Ro, GAS_CO);


if (c == 0) {
  uint16_t valMQ = MQGetGasPercentage(MQRead(MQ_SENSOR_ANALOG_PIN) / Ro, GAS_CO);

@Reza
You are sending a 16 bits signed integer, so the maximum value is 32767.

send(msg.set((int16_t)ceil(valMQ)));

Try to send GAS_SMOKE instead of GAS_CO.
Pay attention to the power supply, the sensor need 5v 200mA ( i misured 130ma).

It should be enough to read ppm from the sensor.

yes, R2 is 1k. Change RL_VALUE from 5 to 1.

I suggest you use the MQ-2 sensor library https://github.com/xerlay11/MQ-2-sensor-library and obviously change log and RL_VALUE.
Regards

1 look at the last line of the sketch:

  return (pow(10, ( ((log(rs_ro_ratio) - pcurve[1]) / pcurve[2]) + pcurve[0])));
}``

change to:

  return (pow(10, ( ((log10(rs_ro_ratio) - pcurve[1]) / pcurve[2]) + pcurve[0])));
}``

2 RL_VALUE in your MQ2 board should be 1 (kohm), R2 in the schematic.

@Reza
there are two problems with MQ-2 sensors :
1 the sketch, at the bottom, uses log instead of log10
2 are you sure that RL_VALUE is 5 (kOhm) in your MQ-2 board? In my is 1, the one labeled 102 in the pic.

Regards