How to define the polling interval and max packet size

uzslm · ‎02-13-2025

SDK for LPC5516 and the example of "dev_hid_generic_lite_bm" :

I believe the polling interval and max packet size were defined in usb_device_descriptor.c:

uint8_t g_UsbDeviceConfigurationDescriptor[] = {

..........................................................................................................................

/* The address of the endpoint on the USB device

described by this descriptor. */

USB_ENDPOINT_INTERRUPT, /* This field describes the endpoint's attributes */

USB_SHORT_GET_LOW(FS_HID_GENERIC_INTERRUPT_IN_PACKET_SIZE),

USB_SHORT_GET_HIGH(FS_HID_GENERIC_INTERRUPT_IN_PACKET_SIZE),

/* Maximum packet size this endpoint is capable of

sending or receiving when this configuration is

selected. */

FS_HID_GENERIC_INTERRUPT_IN_INTERVAL, /* Interval for polling endpoint for data transfers. */

USB_DESCRIPTOR_LENGTH_ENDPOINT, /* Size of this descriptor in bytes */

USB_DESCRIPTOR_TYPE_ENDPOINT, /* ENDPOINT Descriptor Type */

USB_HID_GENERIC_ENDPOINT_OUT | (USB_OUT << USB_DESCRIPTOR_ENDPOINT_ADDRESS_DIRECTION_SHIFT),

/* The address of the endpoint on the USB device

described by this descriptor. */

USB_ENDPOINT_INTERRUPT, /* This field describes the endpoint's attributes */

USB_SHORT_GET_LOW(FS_HID_GENERIC_INTERRUPT_OUT_PACKET_SIZE),

USB_SHORT_GET_HIGH(FS_HID_GENERIC_INTERRUPT_OUT_PACKET_SIZE),

/* Maximum packet size this endpoint is capable of

sending or receiving when this configuration is

selected. */

FS_HID_GENERIC_INTERRUPT_OUT_INTERVAL, /* Interval for polling endpoint for data transfers. */

};

but in hid_generic.c:

case kUSB_DeviceEventSetConfiguration:

..........................................................................................................................

if (USB_SPEED_HIGH == g_UsbDeviceHidGeneric.speed)

{

epInitStruct.maxPacketSize = HS_HID_GENERIC_INTERRUPT_IN_PACKET_SIZE;

epInitStruct.interval = HS_HID_GENERIC_INTERRUPT_IN_INTERVAL;

}

else

{

epInitStruct.maxPacketSize = FS_HID_GENERIC_INTERRUPT_IN_PACKET_SIZE;

epInitStruct.interval = FS_HID_GENERIC_INTERRUPT_IN_INTERVAL;

}

USB_DeviceInitEndpoint(handle, &epInitStruct, &epCallback);

epCallback.callbackFn = USB_DeviceHidGenericInterruptOut;

epCallback.callbackParam = handle;

epInitStruct.zlt = 0U;

epInitStruct.transferType = USB_ENDPOINT_INTERRUPT;

epInitStruct.endpointAddress =

USB_HID_GENERIC_ENDPOINT_OUT | (USB_OUT << USB_DESCRIPTOR_ENDPOINT_ADDRESS_DIRECTION_SHIFT);

if (USB_SPEED_HIGH == g_UsbDeviceHidGeneric.speed)

{

epInitStruct.maxPacketSize = HS_HID_GENERIC_INTERRUPT_OUT_PACKET_SIZE;

epInitStruct.interval = HS_HID_GENERIC_INTERRUPT_OUT_INTERVAL;

}

else

{

epInitStruct.maxPacketSize = FS_HID_GENERIC_INTERRUPT_OUT_PACKET_SIZE;

epInitStruct.interval = FS_HID_GENERIC_INTERRUPT_OUT_INTERVAL;

}

..........................................................................................................................

I have been confused by two code blocks above;

As my previous project from other MCU, they have been defined and fixed in related descriptors entity;

Please kindly advise,mainly i want to define a high speed interrupt in and out endpoint with the best polling interval as 125us.

Thank you very much!

Kind Regards,

uzslm

Alice_Yang · ‎02-18-2025

Hello @uzslm

Please tell us Is there any issue after your configuration with g_UsbDeviceConfigurationDescriptor []?

Thank you.

BR

Alice