@Override
    public void close() throws IOException {
        if (mConnection == null) {
            throw new IOException("Already closed");
        }
        UsbRequest usbRequest = mUsbRequest;
        mUsbRequest = null;
        try {
            usbRequest.cancel();
        } catch(Exception ignored) {}
        try {
            closeInt();
        } catch(Exception ignored) {}
        try {
            mConnection.close();
        } catch(Exception ignored) {}
        mConnection = null;
    }
Sets the size of the internal buffer used to exchange data with the USB
stack for write operations.  Most users should not need to change this.

@param bufferSize the size in bytes, <= 0 resets original size
usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java