ATtiny45 firmware

  usbconfig.h
  -----------
    #define  USB_CFG_VENDOR_ID       0x42, 0x42
    #define  USB_CFG_DEVICE_ID       0x02, 0x00

  main.c 
  ------
  /* USB report descriptor */
    PROGMEM char usbHidReportDescriptor[USB_CFG_HID_REPORT_DESCRIPTOR_LENGTH] = { 
      0x05, 0x01,        // USAGE_PAGE (Generic Desktop = 01)
    	0x09, 0x05,        // USAGE (Game Pad = 05)
    	0xa1, 0x01,        // COLLECTION (Application)
    	0x09, 0x01,        //   USAGE (Pointer)
    	0xa1, 0x00,        //   COLLECTION (Physical)
    	0x09, 0x30,        //     USAGE (X)
    	0x09, 0x31,        //     USAGE (Y)
    	0x15, 0x00,        //   LOGICAL_MINIMUM (0)
    	0x26, 0xff, 0x00,  //   LOGICAL_MAXIMUM (255)
    	0x75, 0x08,        //   REPORT_SIZE (8bits)
    	0x95, 0x04,        //   REPORT_COUNT (2)
    	0x81, 0x02,        //   INPUT (Data,Var,Abs)
    	0xc0,              // END_COLLECTION
    
    static void buildReport(void)
    {
    	reportBuffer[0] = adcval1>>8;
    	reportBuffer[1] = adcval1;
    	reportBuffer[2] = adcval2>>8;
    	reportBuffer[3] = adcval2;    
    	reportBuffer[4] = 0x01;
    }

    usbDeviceConnect();
    adcInit();
    usbInit();
    sei();
	  setIsRecording(1);
    for(;;){    /* main event loop */
        wdt_reset();
        usbPoll();
        if(usbInterruptIsReady() ){ /* we can send a report */
            buildReport();
            usbSetInterrupt(reportBuffer, sizeof(reportBuffer));
        }
        adcPoll();
    }

Application Interfacing with USB

1. Register the application with Windows when the form is created. This enables the application to be notified of USB events eg. device insertion or removal.
   

       protected override void OnHandleCreated(EventArgs e)
       {
         base.OnHandleCreated(e);
         usb.RegisterHandle(base.Handle);
       }
   

2. When a USB device is inserted or removed, the WndProc method is invoked by Windows which then parses the device change messages. More events are triggered as a result of the parsing.

       protected override void WndProc(ref Message m)
       {
         usb.ParseMessages(ref m);
         base.WndProc(ref m);
       }
       
       private void usb_OnDeviceArrived(object sender, EventArgs e)
       {
         this.toolStripStatusLabel1.Text = "Found a Device";
       }
   
   

3. When the Start button is clicked, the PC identifies the attached USB device when it scans through a list of USB device descriptors during a process called enumeration.

       private void btn_ok_Click(object sender, EventArgs e)
       {
         usb.ProductId = int.Parse(this.tb_product.Text, HexNumber);
         usb.VendorId = int.Parse(this.tb_vendor.Text, HexNumber);
         usb.CheckDevicePresent();
       }
       
       public void CheckDevicePresent()
       {
           try
           {
               specified_device = SpecifiedDevice.FindSpecifiedDevice(this.vendor_id, this.product_id);
               // look for the device on the USB bus
               if (specified_device != null)	// did we find it?
               {
                   if (OnSpecifiedDeviceArrived != null)
                   {
                       this.OnSpecifiedDeviceArrived(this, new EventArgs());
                       specified_device.DataReceived += new DataReceivedEventHandler(OnDataReceived);
                       specified_device.DataSend += new DataSendEventHandler(OnDataSend);
                   }
               }
               else
               {
                   if (OnSpecifiedDeviceRemoved != null && history)
                   {
                       this.OnSpecifiedDeviceRemoved(this, new EventArgs());
   
   

4. After the USB device is enumerated, the application obtains data from it when an event is dispatched by the USB library on receiving data from the HID driver.

       private void usb_OnDataReceived(object sender, DataReceivedEventArgs args)
       {
         float num = ((args.data[1] * 0x100) + args.data[2]) * 0.92f;
         float num2 = ((args.data[3] * 0x100) + args.data[4]) * 0.92f;
         graphics.DrawLine(Pens.Black, this.ti + 1, 0, this.ti + 1, this.pictureBox1.Height);
       }