Transferring Data Usb

How to transfer data with high speed through USB?

Seems like you are trying to do some quite sophisticated thing.
First I would like to say that USB is not some kind of port which you can read data "byte after byte" like in case of serial or parallel ports.

I would recommend you to start with reading about USB 2.0 and EHCI documentation (it take some time). Additionally you need to know what kind of USB is your board - is it host or device USB type? In case of usb device type - probably you need to write your own driver for this board and connect it to some USB host (PC for example). Then you need to create some communication protocol over USB. Luckily on the PC side you would use the libusb library for this. I mean you need to write program which uses libusb library for communication with your board.

Quite a lot of work to do.

Transferring data USB

I was trying to send data over the wrong baud rate.

Here's the code that works. Posting it for everyone who is using FTDI devices and needs help.

private Runnable mLoop = new Runnable() {

        @Override
        public void run() {
            UsbDevice dev = sDevice;
            if (dev == null)
                return;
            UsbManager usbm = (UsbManager) getSystemService(USB_SERVICE);
            UsbDeviceConnection conn = usbm.openDevice(dev);
            l("Interface Count: " + dev.getInterfaceCount());
            l("Using "
                    + String.format("%04X:%04X", sDevice.getVendorId(),
                            sDevice.getProductId()));

            if (!conn.claimInterface(dev.getInterface(0), true))
                return;

            conn.controlTransfer(0x40, 0, 0, 0, null, 0, 0);// reset
                                                            // mConnection.controlTransfer(0×40,
                                                            // 0, 1, 0, null, 0,
                                                            // 0);//clear Rx
            conn.controlTransfer(0x40, 0, 2, 0, null, 0, 0);// clear Tx
            conn.controlTransfer(0x40, 0x02, 0x0000, 0, null, 0, 0);// flow
                                                                    // control
                                                                    // none
            conn.controlTransfer(0x40, 0x03, 0x0034, 0, null, 0, 0);// baudrate
                                                                    // 57600
            conn.controlTransfer(0x40, 0x04, 0x0008, 0, null, 0, 0);// data bit
                                                                    // 8, parity
                                                                    // none,
                                                                    // stop bit
                                                                    // 1, tx off

            UsbEndpoint epIN = null;
            UsbEndpoint epOUT = null;

            byte counter = 0;

            UsbInterface usbIf = dev.getInterface(0);
            for (int i = 0; i < usbIf.getEndpointCount(); i++) {
                l("EP: "
                        + String.format("0x%02X", usbIf.getEndpoint(i)
                                .getAddress()));
                if (usbIf.getEndpoint(i).getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
                    l("Bulk Endpoint");
                    if (usbIf.getEndpoint(i).getDirection() == UsbConstants.USB_DIR_IN)
                        epIN = usbIf.getEndpoint(i);
                    else
                        epOUT = usbIf.getEndpoint(i);
                } else {
                    l("Not Bulk");
                }
            }

            for (;;) {// this is the main loop for transferring
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                String get = "$fDump G" + "\n";
                l("Sending: " + get);

                byte[] by = get.getBytes();

                // This is where it sends
                l("out " + conn.bulkTransfer(epOUT, by, by.length, 500));

                // This is where it is meant to receive
                byte[] buffer = new byte[4096];

                StringBuilder str = new StringBuilder();

                if (conn.bulkTransfer(epIN, buffer, 4096, 500) >= 0) {
                    for (int i = 2; i < 4096; i++) {
                        if (buffer[i] != 0) {
                            str.append((char) buffer[i]);
                        } else {
                            l(str);
                            break;
                        }
                    }

                }
                // this shows the complete string
                l(str);

                if (mStop) {
                    mStopped = true;
                    return;
                }
                l("sent " + counter);
                counter++;
                counter = (byte) (counter % 16);
            }
        }
    };

Android to android data transfer using usb

After reading further I was able to identify the problem. I had to force accessory mode in device from host, by sending special controlTransfer messages.

I found it here

https://github.com/peyo-hd/TcpDisplay/blob/master/sink/src/com/android/accessorydisplay/sink/SinkActivity.java

sendString(conn, UsbAccessoryConstants.ACCESSORY_STRING_MANUFACTURER, MANUFACTURER);
sendString(conn, UsbAccessoryConstants.ACCESSORY_STRING_MODEL, MODEL);
sendString(conn, UsbAccessoryConstants.ACCESSORY_STRING_DESCRIPTION, DESCRIPTION);
sendString(conn, UsbAccessoryConstants.ACCESSORY_STRING_VERSION, VERSION);
sendString(conn, UsbAccessoryConstants.ACCESSORY_STRING_URI, URI);
sendString(conn, UsbAccessoryConstants.ACCESSORY_STRING_SERIAL, SERIAL);

// The device should re-enumerate as an accessory.
conn.controlTransfer(UsbConstants.USB_DIR_OUT | UsbConstants.USB_TYPE_VENDOR,
    UsbAccessoryConstants.ACCESSORY_START, 0, 0, null, 0, 10000);

Transferring data to USB Device using controlTransfer

First of all, you should check the spec regarding USB Device like Universal Serial Bus Device Class Definition for Audio Devices.

In the spec you can easily find 'Control Request Layout' like below capture.

And the below link is a web page for you about USB.
http://www.beyondlogic.org/usbnutshell/usb6.shtml#SetupPacket

Can we transfer android data to desktop app via simple USB cable?

I success to transfer android data to desktop java app via simple USB cable with jMTP library.

You can see how in my anwser here

Hope it help.

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