HC-SR04 Ultrasonic Distance Meter | Flutter With Arduino

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Components Used

Components	AliExpress	Amazon	Banggood
Arduino Nano (in this project I have used nano 33 but old nano will also work)
Bread Board
Jumper Wires
HC-SR04 Ultrasonic Module

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Circuit

Connect the Arduino and HC-SR04 module as per the above circuit diagram, you can use any digital pins of Arduino for the echo and trigger pin but make sure it’s the same as both in the circuit and the code.

Arduino	HC- SR04
5V	Vcc
Digital pin 2	Trig  ( Trigger Pulse Input  )
Digital pin 3	Echo(  Echo Pulse Output )
GND	GND

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Arduino Code

Upload the below code to the Arduino nano, the code is very basic it just read the data from the HC-SR04 ultrasonic module and convert it to centimeter and print it to the serial.

const int trig = 2, echo = 3;
long duration, Distanceincm;
void setup() {
  Serial.begin(115200);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
}

void loop() {
  digitalWrite(trig, HIGH);
  delay(15);
  digitalWrite(trig, LOW);
  duration = pulseIn(echo, HIGH);
  Distanceincm = duration / 58; 
  Serial.println(Distanceincm);
  delay(500);
}

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Flutter App

The code and instructions for the flutter app are given below.

Packages Used

usb_serial 0.3.0	https://pub.dev/packages/usb_serial
syncfusion_flutter_gauges 19.2.51	https://pub.dev/packages/syncfusion_flutter_gauges

Add the above packages to the pubspec.yaml file as shown below. Note that the usb_serial 0.3.0 package will only support android, no support for iPhone.

dependencies:
  flutter:
    sdk: flutter
  syncfusion_flutter_gauges: ^19.2.51
  usb_serial: ^0.3.0

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Dart Code

import 'dart:async';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:usb_serial/transaction.dart';
import 'package:usb_serial/usb_serial.dart';
import 'package:syncfusion_flutter_gauges/gauges.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  UsbPort? _port;
  String _status = "Idle";
  List<Widget> _ports = [];
  List<Widget> _serialData = [];
  double myValue = 0;

  StreamSubscription<String>? _subscription;
  Transaction<String>? _transaction;
  UsbDevice? _device;

  Future<bool> _connectTo(device) async {
    _serialData.clear();

    if (_subscription != null) {
      _subscription!.cancel();
      _subscription = null;
    }

    if (_transaction != null) {
      _transaction!.dispose();
      _transaction = null;
    }

    if (_port != null) {
      _port!.close();
      _port = null;
    }

    if (device == null) {
      _device = null;
      setState(() {
        _status = "Disconnected";
      });
      return true;
    }

    _port = await device.create();
    if (await (_port!.open()) != true) {
      setState(() {
        _status = "Failed to open port";
      });
      return false;
    }
    _device = device;

    await _port!.setDTR(true);
    await _port!.setRTS(true);
    await _port!.setPortParameters(
        115200, UsbPort.DATABITS_8, UsbPort.STOPBITS_1, UsbPort.PARITY_NONE);

    _transaction = Transaction.stringTerminated(
        _port!.inputStream as Stream<Uint8List>, Uint8List.fromList([13, 10]));

    _subscription = _transaction!.stream.listen((String line) {
      setState(() {
        _serialData.clear();
        _serialData.add(Text(
          line + "CM",
          style: TextStyle(
              fontSize: 20, color: Colors.green, fontWeight: FontWeight.bold),
        ));

        myValue = double.parse(line);
      });
    });

    setState(() {
      _status = "Connected";
    });
    return true;
  }

  void _getPorts() async {
    _ports = [];
    List<UsbDevice> devices = await UsbSerial.listDevices();
    if (!devices.contains(_device)) {
      _connectTo(null);
    }
    print(devices);

    devices.forEach((device) {
      _ports.add(ListTile(
          leading: Icon(Icons.usb),
          title: Text(device.productName!),
          subtitle: Text(device.manufacturerName!),
          trailing: ElevatedButton(
            child: Text(_device == device ? "Disconnect" : "Connect"),
            onPressed: () {
              _connectTo(_device == device ? null : device).then((res) {
                _getPorts();
              });
            },
          )));
    });

    setState(() {
      print(_ports);
    });
  }

  @override
  void initState() {
    super.initState();
    UsbSerial.usbEventStream!.listen((UsbEvent event) {
      _getPorts();
    });
    _getPorts();
  }

  @override
  void dispose() {
    super.dispose();
    _connectTo(null);
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('HC SR04 Distance'),
        ),
        body: Center(
          child: Column(
            children: <Widget>[
              SfRadialGauge(
                axes: <RadialAxis>[
                  RadialAxis(
                    axisLineStyle: AxisLineStyle(color: Colors.blue),
                    minimum: 0,
                    maximum: 200,
                    pointers: <GaugePointer>[
                      NeedlePointer(value: myValue),
                    ],
                  ),
                ],
              ),
              ..._serialData,
              ..._ports,
              Text('Status: $_status\n'),
              Card(
                child: Text(
                  'https://diyusthad.com',
                  style: TextStyle(color: Colors.yellow.shade700),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

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