Help to compare uint8_t with uint16_t hex value modus project

Using Arduino Programming Questions
1

I am working on a project that reads data from various modbus sensors using the modbusmaster library.

In one sensor i read 3 16 bit registers to get the time from the sensor with this.

    void node5_rtu_time(){
      uint8_t j, result;
      node.setSlaveId(Node_5);
      // slave: read (8) 16-bit registers starting at register 0 to RX buffer
      result = node.readHoldingRegisters(52, 3);
      if (result == 224 || result == 226){
        delay(100);
        result = node.readHoldingRegisters(52, 3);
      }      
      #ifdef MQTT_NODEFUNC_DEBUG
        Serial.print("Node_5 Result: ");
        Serial.print(result);
        Serial.print(" : ");
      #endif
      if (result == node.ku8MBSuccess)
      {     
        for (j = 0; j < 3; j++)
        {
          node5_time[j] = node.getResponseBuffer(j);    
          #ifdef MQTT_NODEFUNC_DEBUG
            Serial.print(node5_time[j], HEX);
            if (j < 2){
              Serial.print(", ");
            }  
          #endif
        }
        #ifdef MQTT_NODEFUNC_DEBUG     
          Serial.print(" -- ");
          Serial.print("EC: ");
          Serial.print(errorcnt);
          Serial.print(" ");        
          Serial.print("CY: ");
          Serial.println(cycle);
          // Serial.println();
        #endif
        RainClockYear = highByte(node5_time[0]);
        RainClockMonth = lowByte(node5_time[0]);
        RainClockDay = highByte(node5_time[1]);
        RainClockHour = lowByte(node5_time[1]);
        RainClockMin = highByte(node5_time[2]);
        RainClockSecond = lowByte(node5_time[2]);
        Serial.print("Rain Sensor Time: ");
        Serial.print(RainClockYear, HEX);
        Serial.print("-");
        Serial.print(RainClockMonth, HEX);
        Serial.print("-");
        Serial.print(RainClockDay, HEX);
        Serial.print(" ");
        Serial.print(RainClockHour, HEX);
        Serial.print(":");
        Serial.print(RainClockMin, HEX);
        Serial.print(":");
        Serial.println(RainClockSecond, HEX);        
        cycle++;
        // send50=true;   
      }         
      else {
        errorcnt++;
        cycle++;
        Serial.print("Node_5 ER: ");
        Serial.print(result);
        Serial.print(" ");      
        Serial.print("EC: ");
        Serial.println(errorcnt);
      }

    }

    
  #endif

The output of the routine is this, and correct if i use the HEX option in the print commands.

Node_5 Result: 0 : 2408, 1915, 5610 -- EC: 0 CY: 0
Rain Sensor Time: 24-8-19 15:56:10

You can see that the time is actually BCD coded into the bytes received and if i use high and low byte i can load the individual numbers into the rain sensor time printout.

All is good but now i have an issue with how to compare the time variables from the rain sensor with the time variables from my rtc on the esp32. I created two conditionals in my setup to do this comparison as follows as a test

  RtcDateTime now = Rtc.GetDateTime();//rtc


  if (!getLocalTime(&timeinfo)) {
    Serial.println("Failed to obtain time");
  }

  second = timeinfo.tm_sec;
  minute = timeinfo.tm_min;
  hour = timeinfo.tm_hour;
  day = timeinfo.tm_yday + 1;
  month = timeinfo.tm_mon + 1;
  year = timeinfo.tm_year + 1900;
  weekday = timeinfo.tm_wday +1;

  node5_rtu_time();

  if(hour != RainClockHour){
    Serial.println("Rtc and RainClockHour does not match");
    Serial.print(hour);
    Serial.print(" = ");
    Serial.println(RainClockHour);
    Serial.print(hour, HEX);
    Serial.print(" = ");
    Serial.println(RainClockHour, HEX);          
  }

  if(hour == RainClockHour){
    Serial.println("Rtc and RainClockHour matches");
    Serial.print(hour);
    Serial.print(" = ");
    Serial.println(RainClockHour);
    Serial.print(hour, HEX);
    Serial.print(" = ");
    Serial.println(RainClockHour, HEX);          
  }

The comparison fails since the rtc hour variable contains 15, but the RainClockHour contains 21. The RainClockHour does contain 15 if i print it as HEX. Here is the output from the code above

Node_5 Result: 0 : 2408, 1915, 5610 -- EC: 0 CY: 0
Rain Sensor Time: 24-8-19 15:56:10
Rtc and RainClockHour does not match
15 = 21
F = 15

Since this one particular sensor likes to embed many variables in this way i do need a way to compare things, i am lost at how to compare the hour variable with the HEX equivalent of the RainClockHour variable and not its decimal value. I am also going to need to load rtc variables back into the 3, 16 bit bytes to send a command to update the time on the sensor if they don't match.

2

I think you need to extract the BCD and convert it to decimal.

Maybe this helps:

uint8_t func(uint16_t value, uint8_t pos)
{
  return (value >> 4*pos) & 0x0f;
}

void setup() {
  Serial.begin(115200);

  uint16_t y = 0x2408;

  uint8_t year2 = func(y, 3) * 10 + func(y, 2);
  Serial.println(year2);
}
3

Choose one representation that allows for easy comparison and convert all values into that format before comparing.