Arduino with Sw420 and RS485 problem

Projects Programming
1

Hi, I'm a beginner in Arduino and the like. I'm trying to connect an Arduino Uno (Slave) which has a SW420 sensor to an Arduino Mega (Master) which has a 16x2 I2C LCD and uses RS485 module as a communication protocol. When trying to run the program, the "GET" command from the master is successfully received by the slave and the slave has successfully sent sensor data. But, on the master, the value received from the slave is always 0 as shown in the screenshot of my serial monitor. Is there someone who can help me solve this problem?

Thank you for your attention.

MASTER CODE

#include <SoftwareSerial.h>
#define enTxPin 4   // HIGH: TX and LOW: RX 
SoftwareSerial mySerial(11, 12); // RX, TX
int value1;
void setup() {
  Serial.begin(9600);
  Serial.println("Starting System");

  mySerial.begin(9600);

  pinMode(enTxPin, OUTPUT);
  digitalWrite(enTxPin, HIGH);       // default TX
}

void loop() {
  mySerial.print("GET%");
  digitalWrite(enTxPin, LOW);       // change pin to RX
  unsigned long timeLimit = millis();
  Serial.println("waiting data");
  while (millis() - timeLimit < 3000) {
    if (mySerial.available()) {
      String dataIN = "";
      Serial.println ("data diterima");
      dataIN = mySerial.read();
      int value1 = dataIN.toInt();
      Serial.println(value1);
      digitalWrite(enTxPin, HIGH);       // default TX
      break;
    }
  }
  Serial.println("waiting loop");
  Serial.println();
  delay(3000);
}

SLAVE CODE

#include <SoftwareSerial.h>
#define enTxPin 4   // HIGH: TX and LOW: RX 
SoftwareSerial mySerial(2, 3); // RX, TX
int vr=9;
int measurement;
String strMeasurement;

void setup() {
  Serial.begin(9600);
  Serial.println("Starting System");

  mySerial.begin(9600);
  pinMode (vr, INPUT);
  pinMode(enTxPin, OUTPUT);
  digitalWrite(enTxPin, LOW);       // default RX
}

void loop() {
  int measurement = vibration();
  Serial.print ("Vr:");
  Serial.print (measurement);
  if (mySerial.available()) {
    String dataIN = "";
    dataIN = mySerial.readStringUntil('%');
    Serial.println(dataIN);
    if (dataIN.substring(0,3) == "GET"){
      digitalWrite(enTxPin, HIGH);       // change pin to HIGH for TX
      String strMeasurement = String (measurement)+ '%';
      mySerial.print(strMeasurement);
      digitalWrite(enTxPin, LOW);       // default RX
      Serial.println("kirim data ke master : " + strMeasurement);
    }
  }

  delay(10);
}

long vibration(){
  long measurement=pulseIn (vr, HIGH);
  delay(1000);
  return measurement;
}

(Right : Master, Left : Slave)

Screenshot (44)
Screenshot (44)1366×768 88.4 KB

2

so continuing from your other thread on the SAME TOPIC, it seems that you need to confirm your sensor is working correctly or not.

did you check that part of your circuit?
this youtube a simple test setup for this sensor:

hope that helps...

3

Yes, the sensor can work well, in the picture above the sensor value is successfully received by the slave node. But when sending to master, the value sent becomes 0;

[image]

4

hmmm... Ok

Maybe they try something simple on the Master side...
something like this maybe:
(Compiles, NOT tested!)

#include <SoftwareSerial.h>
#define enTxPin 4   // HIGH: TX and LOW: RX 
SoftwareSerial mySerial(11, 12); // RX, TX
int value1;
void setup() {
  Serial.begin(9600);
  Serial.println("Starting System");

  mySerial.begin(9600);

  pinMode(enTxPin, OUTPUT);
  digitalWrite(enTxPin, HIGH);       // Ready to Transmit
}

void loop() {
  digitalWrite(enTxPin, HIGH);       //Set to Transmit Mode
  delay(1);                        //small arbitrary delay
  mySerial.print("GET%");              //Tramsit Request
  digitalWrite(enTxPin, LOW);       // Set to Receive Mode
  Serial.println("waiting data");
  delay(3000);
  if (mySerial.available()) {
    Serial.println ("data diterima");
    char dataIN = mySerial.read();
    while (mySerial.available()) {
      Serial.println(dataIN);
    }
  }
}

Hope that helps...

5

first of all if you have 4 hardware UART's available you should not use swSerial really, but this is not your issue.

mySerial.print("GET%");
  digitalWrite(enTxPin, LOW);       // change pin to RX

swSerial is non-blocking' and if you are using RS485 bi-directional, you should make sure that the sending of the message has completed before you disable TX on the RS485

mySerial.print("GET%");
mySerial.flush();
delay(10);   // wait another whole byte to be sure
  digitalWrite(enTxPin, LOW);       // change pin to RX

on the slave end.

if (mySerial.available()) {
    String dataIN = "";

like this you maky not be reading the whole message to begin with. At 9600bps, a byte takes about 1 ms to transmit, but this is a different matter. The Serial reception method does not look very reliable to me, but that doesn't mean you may not be able to get it working at all. Still adding a small delay here as well will improve things.

if (mySerial.available()) {
    delay(100);  // you will wait for 3000ms for a response so we have some time to fill the buffer.
    String dataIN = "";

Main thing to make sure is that the transmission of any data is complete before you switch the RS485 unit to RX and that you don't start responding until the reception of any dat has been completed. You don't want both units in TX mode at the same time, they may (and will) break.
so

if (dataIN.substring(0,3) == "GET"){
      while (mySerial.available()) {
           char c = mySerial.read();
           delay(10);
        }
      digitalWrite(enTxPin, HIGH);       // change pin to HIGH for TX

And rather than having the master defaulting as TX. Keep it in RX mode until you decide to transmit a request.

6

still not working, master doesn't stop while looping. Hmm I guess I'll try a few more ways until it works.

7

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