Max size of HID report descriptor.

Question

Hi
Could I modify HID report descriptor length over 255 bytes? In Desktop1.2.2.293, the returned descriptor size is only decided by wLength LSB byte and ignores MSB byte. 
 Jeffery

Håkon Alseth · Accepted Answer

Hi Jeffery, 
 Each descriptor has it's own field called "bLength", which is per. HID spec, one byte.
This means that your specific descriptor is max. 255 byte. 
 However, descriptors are segmented. Meaning that you can have many descriptors which all-in-all exceeds 255 byte. One for mouse, one for keyboard, one for audio, etc. 
 If you look at usb_desc.c in nRFready desktop, array g_usb_hid_hids[], you will see that each descriptor has it's own bLength (the sizeof(hid_desc)). 
 I am not sure if this answers your question.
Please steer me in the right direction if I have not fully understood your question. 
 Another note: we have an application note, nAN-22, which is about USB transfers and HID usage:
 www.nordicsemi.com/.../10134192 
 Best regards
Håkon