Java provides powerful capabilities for embedded systems development, from IoT devices to real-time systems. This guide covers everything you need to know about embedded Java development.
Key areas covered:
public class EmbeddedApplication {
public static void main(String[] args) {
// Initialize system properties
System.setProperty("microedition.configuration",
"CLDC-1.1");
System.setProperty("microedition.profiles",
"IMP-NG");
// Initialize device
try {
DeviceManager.initialize();
startApplication();
} catch (Exception e) {
System.err.println("Initialization failed: " +
e.getMessage());
}
}
private static void startApplication() {
// Application initialization
Display display = Display.getDisplay(null);
MainForm form = new MainForm();
display.setCurrent(form);
}
}public class GPIOController {
private final GpioController gpio;
private final GpioPinDigitalOutput led;
public GPIOController() {
gpio = GpioFactory.getInstance();
led = gpio.provisionDigitalOutputPin(
RaspiPin.GPIO_01,
"LED",
PinState.LOW);
}
public void toggleLED() {
led.toggle();
}
public void setLEDState(boolean state) {
led.setState(state);
}
public void cleanup() {
gpio.shutdown();
}
}public class RealTimeTask extends RealtimeThread {
private final PeriodicParameters period;
private final PriorityParameters priority;
private volatile boolean running = true;
public RealTimeTask(long periodMs, int priority) {
this.period = new PeriodicParameters(
new RelativeTime(periodMs, 0));
this.priority = new PriorityParameters(priority);
setSchedulingParameters(this.priority);
setReleaseParameters(this.period);
}
@Override
public void run() {
while (running) {
// Perform real-time task
processData();
// Wait for next period
waitForNextPeriod();
}
}
private void processData() {
try {
// Critical real-time processing
MemoryArea.getMemoryArea(this)
.executeInArea(() -> {
// Process data in real-time
});
} catch (Exception e) {
System.err.println("Real-time processing error: " +
e.getMessage());
}
}
public void stopTask() {
running = false;
}
}public class SensorManager {
private final Map sensors =
new ConcurrentHashMap<>();
private final ScheduledExecutorService scheduler =
Executors.newScheduledThreadPool(1);
public void registerSensor(String id, Sensor sensor) {
sensors.put(id, sensor);
scheduleSensorReading(id, sensor);
}
private void scheduleSensorReading(String id,
Sensor sensor) {
scheduler.scheduleAtFixedRate(() -> {
try {
SensorReading reading = sensor.read();
processReading(id, reading);
} catch (Exception e) {
log.error("Error reading sensor {}: {}",
id, e.getMessage());
}
}, 0, sensor.getReadInterval(),
TimeUnit.MILLISECONDS);
}
private void processReading(String id,
SensorReading reading) {
// Process and store sensor data
DataProcessor.process(id, reading);
// Check thresholds
if (reading.getValue() > reading.getThreshold()) {
triggerAlert(id, reading);
}
}
private void triggerAlert(String id,
SensorReading reading) {
AlertManager.sendAlert(new Alert(
id,
reading.getValue(),
reading.getTimestamp(),
AlertLevel.HIGH
));
}
} public class MQTTClient {
private final MqttClient client;
private final String topic;
public MQTTClient(String broker, String clientId,
String topic) throws MqttException {
this.client = new MqttClient(broker, clientId);
this.topic = topic;
MqttConnectOptions options = new MqttConnectOptions();
options.setCleanSession(true);
options.setAutomaticReconnect(true);
client.connect(options);
client.setCallback(new MqttCallback() {
@Override
public void messageArrived(String topic,
MqttMessage message) {
processMessage(topic, message);
}
@Override
public void connectionLost(Throwable cause) {
log.error("Connection lost", cause);
}
@Override
public void deliveryComplete(
IMqttDeliveryToken token) {
log.info("Message delivered");
}
});
client.subscribe(topic);
}
public void publishMessage(String message)
throws MqttException {
MqttMessage mqttMessage =
new MqttMessage(message.getBytes());
client.publish(topic, mqttMessage);
}
private void processMessage(String topic,
MqttMessage message) {
// Process received message
String payload = new String(message.getPayload());
MessageProcessor.process(topic, payload);
}
}public class MemoryOptimizer {
private static final int BUFFER_SIZE = 1024;
private final ByteBuffer directBuffer;
public MemoryOptimizer() {
// Use direct ByteBuffer for better performance
directBuffer = ByteBuffer.allocateDirect(
BUFFER_SIZE);
}
public void processData(byte[] data) {
// Reuse buffer
directBuffer.clear();
directBuffer.put(data);
directBuffer.flip();
// Process data
while (directBuffer.hasRemaining()) {
// Process buffer contents
}
}
public void optimizeMemory() {
// Suggest garbage collection
System.gc();
// Wait for finalizers
System.runFinalization();
// Clear soft references
CacheManager.clearCache();
}
}Java provides powerful capabilities for embedded systems development. By following the patterns and practices outlined in this guide, you can effectively develop robust embedded applications.
Remember to focus on optimization, resource management, and proper testing for reliable embedded systems.