How to read and write data to COM/Serial ports in Android?

Introduction

This article guides you through the process of reading and writing data to COM/Serial ports in Android applications. Serial communication is essential for interfacing with various devices, such as microcontrollers, sensors, and GPS modules.

Understanding Serial Communication

Serial communication transmits data bit-by-bit over a single wire, typically using protocols like RS-232 or UART. Android provides APIs to interact with these ports.

Types of Serial Ports

• RS-232: A common standard for serial communication, often used with older devices.
• UART (Universal Asynchronous Receiver/Transmitter): A more modern and flexible standard commonly found in embedded systems.

Prerequisites

• Android Studio: The official integrated development environment (IDE) for Android development.
• USB-to-Serial Adapter: Necessary for connecting a serial device to your Android phone or emulator.
• Device Drivers: Ensure proper drivers are installed on your system for the USB-to-serial adapter.

Steps to Read and Write Data

1. Obtain Permissions

In your AndroidManifest.xml file, declare the READ_EXTERNAL_STORAGE permission for accessing external storage, where you might store configuration files.

2. Import Necessary Libraries

import android.os.Bundle;
import android.util.Log;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import android.app.Activity;
import android.content.Context;
import android.hardware.usb.UsbDevice;
import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbManager;
import android.widget.Toast;
import com.hoho.android.usbserial.driver.UsbSerialDriver;
import com.hoho.android.usbserial.driver.UsbSerialPort;
import com.hoho.android.usbserial.driver.UsbSerialProber;
import com.hoho.android.usbserial.util.SerialInputOutputManager;

3. Find the Serial Port

Utilize the UsbSerialProber to search for available serial ports.

public void findSerialPort() {
UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
UsbDevice device = null;
for (UsbDevice usbDevice : usbManager.getDeviceList().values()) {
if (usbDevice.getDeviceName().contains("your_device_name")) { // Replace "your_device_name"
device = usbDevice;
break;
}
}
UsbSerialDriver driver = UsbSerialProber.probe(device);
if (driver != null) {
UsbSerialPort port = driver.getPorts().get(0); // Choose the port you want to use
// Proceed to open and configure the port
} else {
// Device not found or not supported
}
}

4. Open and Configure the Port

UsbSerialPort port; // Your selected port
try {
// Request permission from the user if needed
UsbDeviceConnection connection = usbManager.openDevice(device);
port.open(connection);
port.setParameters(115200, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE);
// Set the baud rate, data bits, stop bits, and parity
} catch (IOException e) {
// Handle any errors
Log.e("SERIAL_PORT", "Error opening and configuring port: " + e.getMessage());
}

5. Read Data from the Port

Utilize a separate thread for reading data from the serial port, as blocking operations can freeze your UI thread.

private final SerialInputOutputManager.Listener listener = new SerialInputOutputManager.Listener() {
@Override
public void onRunError(Exception e) {
Log.d(TAG, "Runner stopped.");
}

@Override
public void onNewData(byte[] data) {
String receivedData = new String(data);
// Process the received data
}
};

private final SerialInputOutputManager serialIoManager = new SerialInputOutputManager(port, listener);
new Thread(serialIoManager, "SerialInputOutputManager").start();

6. Write Data to the Port

Write data to the serial port using the write() method. Ensure the data is formatted correctly based on your device’s communication protocol.

try {
byte[] data = "Hello World!".getBytes();
port.write(data, 1000); // Write data to the port
} catch (IOException e) {
Log.e("SERIAL_PORT", "Error writing data to port: " + e.getMessage());
}

7. Close the Port

After you finish using the serial port, close it to release resources.

try {
port.close();
} catch (IOException e) {
Log.e("SERIAL_PORT", "Error closing port: " + e.getMessage());
}

Conclusion

By following these steps and understanding the basic concepts, you can effectively read and write data to COM/Serial ports in Android applications. This enables communication with various devices and unlocks a wide range of possibilities for your app’s functionality.