LPC4357 USB HID OUT endpoint problem

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by GTA on Tue Jul 30 14:36:27 MST 2013
Hello All,

I am using an LPC4357 Embedded Artists dev board and LPCOpen to create a USB HID device with one interrupt IN and one OUT endpoint (endpoints 1 and 2). The HID device enumerates OK and I am able to correctly send info device->host via the IN endpoint. However, despite configuring the OUT endpoint it does not seem to register any data being sent to it from the host.

I saw this in HIDClassDevice.h for USB_ClassInfo_HID_Device_t:

@note Due to technical limitations, the HID device class driver does not utilize a separate OUT
*        endpoint for host->device communications. Instead, the host->device data (if any) is sent to
*        the device via the control endpoint.

Before going into full detail on low level USB controller debugging, what are those "technical limitations"? Is there something fundamental preventing me from implementing a HID interrupt OUT endpoint? Or is it just that support for it is not yet implemented in the HID class stack (or not considered important enough)?