USB driver patch

Refactored SerialInputOutputManager:

- Implemented multiple read buffers to improve USB reading efficiency and reduce latency.
- Used separate threads for reading and writing, enhancing concurrency and performance.
- Removed read timeouts, as they are not necessary for event-driven data reading.

These changes enhance the responsiveness, reliability, and robustness of USB communication.

Author: dkaukov

android-src/KV4PHT/app/src/main/java/com/vagell/kv4pht/radio/RadioAudioService.java

@@ -931,8 +931,8 @@ public void onRunError(Exception e) {
             }
         });
         usbIoManager.setWriteBufferSize(90000); // Must be large enough that ESP32 can take its time accepting our bytes without overrun.
-        usbIoManager.setReadTimeout(1000); // Must not be 0 (infinite) or it may block on read() until a write() occurs.
-        usbIoManager.start();
+        usbIoManager.setReadBufferSize(1024/4); // Must not be 0 (infinite) or it may block on read() until a write() occurs.
+        usbIoManager.setReadBufferCount(16*4);
         checkedFirmwareVersion = false;
 
         Log.d("DEBUG", "Connected to ESP32.");
@@ -1217,43 +1217,7 @@ public synchronized void sendBytesToESP32(byte[] newBytes) {
             Log.d("DEBUG", "Warning: Attempted to send bytes to ESP32 while in the process of flashing a new firmware.");
             return;
         }
-
-        int usbRetries = 0;
-        try {
-            // usbIoManager.writeAsync(newBytes); // On MCUs like the ESP32 S2 this causes USB failures with concurrent USB rx/tx.
-            int bytesWritten = 0;
-            int totalBytes = newBytes.length;
-            final int MAX_BYTES_PER_USB_WRITE = 128;
-            do {
-                try {
-                    byte[] arrayPart = Arrays.copyOfRange(newBytes, bytesWritten, Math.min(bytesWritten + MAX_BYTES_PER_USB_WRITE, totalBytes));
-                    serialPort.write(arrayPart, 200);
-                    bytesWritten += MAX_BYTES_PER_USB_WRITE;
-                    usbRetries = 0;
-                } catch (SerialTimeoutException ste) {
-                    // Do nothing, we'll try again momentarily. ESP32's serial buffer may be full.
-                    usbRetries++;
-                    Log.d("DEBUG", "usbRetries: " + usbRetries);
-                }
-            } while (bytesWritten < totalBytes && usbRetries < 10);
-            // Log.d("DEBUG", "Wrote data: " + Arrays.toString(newBytes));
-        } catch (Exception e) {
-            e.printStackTrace();
-            try {
-                serialPort.close();
-            } catch (Exception ex) {
-                // Ignore. We did our best to close it!
-            }
-            try {
-                Thread.sleep(1000);
-            } catch (InterruptedException ex) {
-                // Ignore. This should only happen if the app is paused in this brief moment between USB retries, not a serious issue.
-            }
-            findESP32Device(); // Attempt to reconnect after the brief pause above.
-        }
-        if (usbRetries == 10) {
-            Log.d("DEBUG", "sendBytesToESP32: Connected to ESP32 via USB serial, but could not send data after 10 retries.");
-        }
+        usbIoManager.writeAsync(newBytes);
     }
 
     public static UsbSerialPort getUsbSerialPort() {

android-src/KV4PHT/usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/DeviceTest.java

@@ -1206,7 +1206,6 @@ private int readSpeedInt(int writeSeconds, int readBufferSize, int readTimeout)
             writeAhead = 50;
 
         usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START));
-        usb.ioManager.setReadTimeout(readTimeout);
         if(readBufferSize > 0)
             usb.ioManager.setReadBufferSize(readBufferSize);
         usb.ioManager.start();
@@ -1383,9 +1382,6 @@ public void IoManager() throws Exception {
         usb.ioManager = new SerialInputOutputManager(usb.serialPort, usb);
         assertEquals(usb, usb.ioManager.getListener());
 
-        assertEquals(0, usb.ioManager.getReadTimeout());
-        usb.ioManager.setReadTimeout(10);
-        assertEquals(10, usb.ioManager.getReadTimeout());
         assertEquals(0, usb.ioManager.getWriteTimeout());
         usb.ioManager.setWriteTimeout(11);
         assertEquals(11, usb.ioManager.getWriteTimeout());
@@ -1399,7 +1395,6 @@ public void IoManager() throws Exception {
 
         usb.ioManager.setReadBufferSize(usb.ioManager.getReadBufferSize());
         usb.ioManager.setWriteBufferSize(usb.ioManager.getWriteBufferSize());
-        usb.ioManager.setReadTimeout(usb.ioManager.getReadTimeout());
         usb.ioManager.setWriteTimeout(usb.ioManager.getWriteTimeout());
         usb.close();
 
@@ -1416,19 +1411,14 @@ public void IoManager() throws Exception {
         } catch (IllegalStateException ignored) {
         }
         try {
-            usb.ioManager.run();
+            usb.ioManager.start();
             fail("already running error expected");
         } catch (IllegalStateException ignored) {
         }
         try {
             usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_LOWEST);
             fail("setThreadPriority IllegalStateException expected");
         } catch (IllegalStateException ignored) {}
-        try {
-            usb.ioManager.setReadTimeout(20);
-            fail("setReadTimeout IllegalStateException expected");
-        } catch (IllegalStateException ignored) {}
-        assertEquals(0, usb.ioManager.getReadTimeout());
         usb.ioManager.setWriteTimeout(21);
         assertEquals(21, usb.ioManager.getWriteTimeout());
         usb.ioManager.setReadBufferSize(22);
@@ -1484,7 +1474,6 @@ public void IoManager() throws Exception {
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_DEFAULT);
-        Executors.newSingleThreadExecutor().submit(usb.ioManager);
         usb.waitForIoManagerStarted();
         try {
             usb.ioManager.start();
@@ -1514,15 +1503,13 @@ public void writeAsync() throws Exception {
 
         // with timeout: write after timeout
         usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START));
-        usb.ioManager.setReadTimeout(100);
         usb.ioManager.start();
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.ioManager.writeAsync(buf);
         usb.ioManager.writeAsync(buf);
         data = telnet.read(2);
         assertEquals(2, data.length);
-        usb.ioManager.setReadTimeout(200);
     }
 
     @Test

android-src/KV4PHT/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java

@@ -33,7 +33,12 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
     protected final UsbDevice mDevice;
     protected final int mPortNumber;
 
-    // non-null when open()
+    @Override
+    public UsbDeviceConnection getConnection() {
+      return mConnection;
+    }
+
+  // non-null when open()
     protected UsbDeviceConnection mConnection = null;
     protected UsbEndpoint mReadEndpoint;
     protected UsbEndpoint mWriteEndpoint;

android-src/KV4PHT/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/UsbSerialPort.java

@@ -281,4 +281,6 @@ enum ControlLine { RTS, CTS,  DTR, DSR,  CD, RI }
      */
     boolean isOpen();
 
+    UsbDeviceConnection getConnection();
+
 }