The application needs to include xud.h.

Create a table of endpoint types for both IN and OUT endpoints. These must each include one for endpoint 0.

#define XUD_EP_COUNT_OUT  1
#define XUD_EP_COUNT_IN   2

/* Endpoint type tables */
XUD_EpType epTypeTableOut[XUD_EP_COUNT_OUT] = {
    XUD_EPTYPE_CTL | XUD_STATUS_ENABLE
};
XUD_EpType epTypeTableIn[XUD_EP_COUNT_IN] = {
    XUD_EPTYPE_CTL | XUD_STATUS_ENABLE, XUD_EPTYPE_BUL
};

The endpoint types are:

• XUD_EPTYPE_ISO: Isochronous endpoint
• XUD_EPTYPE_INT: Interrupt endpoint
• XUD_EPTYPE_BUL: Bulk endpoint
• XUD_EPTYPE_CTL: Control endpoint
• XUD_EPTYPE_DIS: Disabled endpoint

And XUD_STATUS_ENABLE is ORed in to the endpoints that wish to be informed of USB bus resets (see Status reporting).

Within the main() function it is necessary to allocate the channels to connect the endpoints and then create the top-level par containing the XUD_Manager, endpoint 0 and any application specific endpoints.

int main()
{
    chan c_ep_out[XUD_EP_COUNT_OUT], c_ep_in[XUD_EP_COUNT_IN];
    par {
        XUD_Manager(c_ep_out, XUD_EP_COUNT_OUT,
                    c_ep_in, XUD_EP_COUNT_IN,
                    null, epTypeTableOut, epTypeTableIn,
                    null, null, null, XUD_SPEED_HS, null);
        Endpoint0(c_ep_out[0], c_ep_in[0]);

        // Application specific endpoints
        ...
    }
    return 0;
}

The XUD_Manager connects to one end of every channel while the other end is passed to an endpoint (either endpoint 0 or an application specific endpoint). Application specific endpoints are connected using channel ends so the IN and OUT channel arrays need to be extended for each endpoint.

Endpoint 0 uses index 0 of both the endpoint type table and the channel array. The address of other endpoints must also correspond to their index in the endpoint table and the channel array.

An application specific endpoint can send data using XUD_SetBuffer() and receive data using XUD_GetBuffer().

It is necessary to create an implementation for endpoint 0 which takes two channels, one for IN and one for OUT. It can take an optional channel for test (see the Test Modes section of XMOS USB Device (XUD) Library).

void Endpoint0(chanend chan_ep0_out, chanend chan_ep0_in, chanend ?c_usb_test)
{

Every endpoint must be initialized using the XUD_InitEp() function. For endpoint 0 this is looks like:

XUD_ep ep0_out = XUD_InitEp(chan_ep0_out);
XUD_ep ep0_in  = XUD_InitEp(chan_ep0_in);

Typically the minimal code for endpoint 0 loops making call to USB_GetSetupPacket(), parses the USB_SetupPacket_t for any class/applicaton specific requests. Then makes a call to USB_StandardRequests(). And finally, calls XUD_ResetEndpoint() if there have been a bus-reset. For example:

while(1)
{
    /* Returns XUD_RES_OKAY on success, XUD_RES_RST for USB reset */
    XUD_Result_t result = USB_GetSetupPacket(ep0_out, ep0_in, sp);

    if(result == XUD_RES_OKAY)
    {
        switch(sp.bmRequestType.Type)
        {
            case BM_REQTYPE_TYPE_CLASS:
                switch(sp.bmRequestType.Receipient)
                {
                    case BM_REQTYPE_RECIP_INTER:
                        // Optional class specific requests.
                        break;

                    ...
                }

                break;

            ...
        }

        result = USB_StandardRequests(ep0_out, ep0_in,
                devDesc, devDescLen, ...);
    }

    if(result ==  XUD_RES_RST)
        usbBusSpeed = XUD_ResetEndpoint(ep0_out, ep0_in);
}

The code above could also over-ride any of the requests handled in USB_StandardRequests() for custom functionality.

Note, class specific code should be inserted before USB_StandardRequests() is called since if USB_StandardRequests() cannot handle a request it marks the Endpoint stalled to indicate to the host that the request is not supported by the device.

USB_StandardRequests() takes char array parameters for device descriptors for both high and full-speed. Note, if null is passed as the full-speed descriptor the high-speed descriptor is used in full-speed mode and vice versa.

Note that on reset the XUD_ResetEndpoint() function returns the negotiated USB speed (i.e. full or high speed).

USB device descriptors must be provided for each USB device. They are used to identify the USB device’s vendor ID, product ID and detail all the attributes of the advice as specified in the USB 2.0 standard. It is beyond the scope of this document to give details of writing a descriptor, please see the relavant USB Specification Documents.

For more details see the worked HID Class example (Basic example HS device: USB HID device).