Serial Communication between Arduino & pi

[Jerwinprabu]

Hello all,

I've been trying for more than a week to communicate from raspberry pi (QT C++) to Arduino (Arduino IDE c++) through a serial port but i keep failing.

I did some searching on google, read the example... and still i didn't succeeded. Ok so the basic thing is that i need to communicate continuously the serial port sent command from Raspberry pi to Arduino. I tried to keep the code as simple as possible.

Initially I'm sending "J" char from raspberry pi (QT C++) to Arduino (Arduino IDE c++) and waiting on that J, to make the LED blink on Arduino. But it doesn't work.. Even I didn't get any sample for interfacing & communicating & sending data raspberry pi (QT C++) to Arduino (Arduino IDE c++). I don't know what is the problem exactly. Kindly help me to solve the issue.

In monitor, 9600 baudrate

I have attached program what I have tried on both side.

main.cpp

#include <iostream>
#include <QIODevice>

#include <QtSerialPort/QSerialPort>
#include <QtSerialPort/QSerialPortInfo>
#include <QString>

using namespace std;

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Dialog w;
    w.show();

    QSerialPort serialPort;
    serialPort.setBaudRate(QSerialPort::Baud9600);

    QSerialPortInfo info("ttyUSB0");
        qDebug() << "Name        : "     << info.portName();
        qDebug() << "Description : "     << info.description();
        qDebug() << "Busy:"              << info.isBusy();

        QSerialPort serial;
        serial.setPortName("ttyUSB0");

        serial.open(QIODevice::ReadWrite);
        serial.setBaudRate(QSerialPort::Baud9600);
        serial.setDataBits(QSerialPort::Data8);
        serial.setParity(QSerialPort::NoParity);
        serial.setStopBits(QSerialPort::OneStop);
        serial.setFlowControl(QSerialPort::NoFlowControl);

        serial.open(QSerialPort::ReadWrite);
        cout<<"Readable    :"<<serial.isReadable()<<endl;
        cout<<"Writable    :"<<serial.isWritable()<<endl<<endl;

        if (serial.isOpen() && serial.isWritable())
        {
            qDebug() << "Is open : " << serial.isOpen() << endl;
            qDebug() << "Is writable : " << serial.isWritable() << endl;

            qDebug() << "Ready..." << endl;
            serial.write("J");

            QByteArray ba("J\n");

            serial.write(ba);
            {
                QByteArray ba("J");
                serial.write(ba);
                serial.flush();
                qDebug() << "data has been send" << endl;
                serial.close();
            }
            if (serial.bytesToWrite() > 0)
            {
                serial.flush();
                if(serial.waitForBytesWritten(1000))
                {
                    qDebug() << "data has been send" << endl;
                }
            }
            if(serial.flush())
                {
                    qDebug() << "ok" << endl;
                }
                qDebug() <<"value sent "<< endl;
                serial.close();
        }
        else
        {
            qDebug() << "An error occured" << endl;
        }
    return a.exec();
}

Arduino code:

int led = 13, avlb = 0;

void setup() 
{ 
Serial.begin(9600); 
pinMode(led, OUTPUT); 
Serial.println("started");
}

void loop() 
{ 

 if (Serial.available() > 0)
{
    Serial.println("available");
    Serial.println(Serial.available());  
    delay(2000); 
    digitalWrite(led, HIGH);  
    delay(5000);           

  if(Serial.read() == 'J')
 {
   Serial.println("read");
   Serial.println(Serial.read());
   delay(2000);
   digitalWrite(led, LOW);   
   delay(1000);  
 }  
}

else
 {
   Serial.println("not available");
   delay(1000);
 }
}

Output Displayed:

Raspberry qt creator ide o/p:

Name        :  "ttyUSB0"
Description :  "FT232R USB UART"
Busy: false

Readable    :1
Writable    :1

Is open :  true 

Is writable :  true 

Ready... 

data has been send 

bool QSerialPort::flush(): device not open
value sent

Arduino Ide Output displayed:

started

not available
not available
not available
not available
not available
not available
not available
not available
not available

[SGaist]

Hi,

I'd recommend starting by using the terminal example to test the connection and communication.

Then, in your code, you are closing the port on several occasions, why ?

[Celal]

@Jerwinprabu said in Communication between Raspberry pi (QT C++) and Arduino (Arduino IDE):

int led = 13, avlb = 0;

void setup()
{
Serial.begin(9600);
pinMode(led, OUTPUT);
Serial.println("started");
}

void loop()
{

if (Serial.available() > 0)
{
Serial.println("available");
Serial.println(Serial.available());
delay(2000);
digitalWrite(led, HIGH);
delay(5000);

if(Serial.read() == 'J')
{
Serial.println("read");
Serial.println(Serial.read());
delay(2000);
digitalWrite(led, LOW);
delay(1000);
}
}

else
{
Serial.println("not available");
delay(1000);
}
}

I do not know, what are you trying to do but your code does send data. You need the check ASCII code for letter 'J' which is 74.

[Jerwinprabu]

@SGaist Thanks for your reply. I will remove that. For checking I have created.