Master and slave code for temperature sensor TMP36

Projects Programming
1

Hi I want to build the master and slaver arduino connected via UART port. In my master code I want it to be able to tell the temperature every time I drag the temperature bar and send out the message: normal, alert, and danger. After the message was sent out the slaver board will use it as the input to turn on individual LED: green, yellow, and red
I was able to get the mastercode to run perfectly fine. However, there was something wrong with my slaver code, it couldn't change anylight other than green. I tried to troubleshoot the issue, but I couldn't understand why, maybe there was sth wrong during the data transfer
This is my master code

char chArray[7];
int tmp36=A0;
int allowableTemp = 0;
double temp;
double tempC;
void setup()
{
Serial.begin(9600);
pinMode(tmp36, INPUT);
}
void loop()
{
allowableTemp = 30;
temp = analogRead(tmp36);
temp = temp / 1024; //* find percentage of input reading
temp = temp * 5; //* multiply by 5V to get voltage
temp = temp - 0.5; //* Subtract the offset
tempC = temp * 100; //* Convert to degree

if (tempC < allowableTemp) //temp below 30
{
strcpy(chArray,"normal"); // blink normal
}
else if (tempC >= allowableTemp && tempC < allowableTemp + 40) //temp between 30 and 70
{
strcpy(chArray,"alert"); //blink alert
}

else //temp above 70
{
strcpy(chArray,"danger");//blink danger
}
}

Slaver code
char roomtemp [7];
int LED1=4;
int LED2=3;
int LED3=2;
void setup ()
{
Serial.begin(9600);
pinMode(LED1, OUTPUT);
pinMode(LED2, OUTPUT);
pinMode(LED3, OUTPUT);
}
void loop ()
{
Serial.readBytes(roomtemp,7);
Serial.println(roomtemp);
if ("normal"){
digitalWrite(LED1,HIGH);
delay(1000);
digitalWrite(LED1,LOW);
delay(1000);
}
else if("alert!"){
digitalWrite(LED2,HIGH);
delay(1000);
digitalWrite(LED2,LOW);
delay(1000);
}
else
{
digitalWrite(LED3,HIGH);
delay(1000);
digitalWrite(LED3,LOW);
delay(1000);
}
}

2

That term is always true (it's a character pointer which is never 0). I guess you're looking for something like strncmp().

1 Like
3

Yes but I don't know how it works, can you tell me a bit more about that command ? can I use it with if condition?

4

1. Connect two Arduinos as per following diagram (Fig-1) using SUART Port (Software UART Port). Also, connect the LEDs as shown.

uartUnoUnoX
Figure-1:

2. Upload the following sketch (your one with slight modifications) in UNO-1.

#include<SoftwareSerial.h>
SoftwareSerial(5, 6);  //DPin-5 = SRX, DPin-6 = STX

char chArray[7];
int tmp36=A0;
int allowableTemp = 0;
double temp;
double tempC;

void setup()
{
    Serial.begin(9600);
    SUART.begin(9600);
    pinMode(tmp36, INPUT);
}

void loop()
{
    allowableTemp = 30;
    temp = analogRead(tmp36);
    temp = temp / 1024; //* find percentage of input reading
    temp = temp * 5; //* multiply by 5V to get voltage
    temp = temp - 0.5; //* Subtract the offset
    tempC = temp * 100; //* Convert to degree

   if (tempC < allowableTemp) //temp below 30
   {
       strcpy(chArray,"normal"); // blink normal
       SUART.println(chArray);       //send message to Slave (UNO-2)
   }
   else if (tempC >= allowableTemp && tempC < allowableTemp + 40) //temp between 30 and 70
   {
         strcpy(chArray,"alert"); //blink alert
         SUART.println(chArray);       //send message to Slave (UNO-2)
   }
   else //temp above 70
  {
      strcpy(chArray,"danger");//blink danger
      SUART.println(chArray);       //send message to Slave (UNO-2)
  }
}

3. Upload the following sketch (your one with slight modification) in Slave (UNO-2).

#include<SoftwareSerial.h>
SoftwareSerial(5, 6);  //DPin-5 = SRX, DPin-6 = STX
char roomtemp [10];
int LED1=4;
int LED2=3;
int LED3=2;
byte m;

void setup ()
{
    Serial.begin(9600);
    SUART.begin(9600);
    pinMode(LED1, OUTPUT);
    pinMode(LED2, OUTPUT);
}

void loop()
{
     while(SUART.available() >0)
     {
            m =  SUART.readBytesUntil('\n', roomtemp, 10);
     }
     roomtemp[m] = '\0';
     
     if(strcmp(roomtemp, "normal") == 0)
     {
                  digitalWrite(LED1, HIGH);
                  delay(1000);
                  digitalWrite(LED1, LOW);
                  delay(1000);
      }
            
      if(strcmp(roomtemp, "alert") == 0)
      {
                  digitalWrite(LED2, HIGH);
                  delay(1000);
                  digitalWrite(LED2, LOW);
                  delay(1000);
      }
            
      if(strcmp(roomtemp, "normal") == 0)
      {
                  digitalWrite(LED1, HIGH);
                  delay(1000);
                  digitalWrite(LED1, LOW);
                  delay(1000);
      } 
}
1 Like
5

@GolamMostafa
Hi, I couldn't find SUART port on my arduino, is it only appear on the software

6

You don't need to worry about it. It is automatically created when you include the following lines (at the places you see in the sketch) in the sketch:

#include<SoftwareSerial.h>
SoftwareSerial SUART(5, 6); //DPin-5 = SRX, DPin-6 = STX
SUART.begin(9660);

Have you tested the sketches of Post#4? Are they working?

1 Like
7

Yes, it works thank you so much

8

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