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USB HS Module, Endpoint number confusion

Question asked by Michael Hermann on Nov 17, 2018
Latest reply on Nov 21, 2018 by Fang Li



I'm working with the K28F-Family which has an EHCI-compatible USB module (USBHS) and the USB Stack (2.0.1).

In general things work quite fine, I was able to implement my own composite devices successfully.

I am, however confused, when it comes to the number of endpoints the module supports. Te document I refer to is the Sub-Family Reference Manual Rev. 4 08/2017.


In 54.2.2 it states: 

Supports eight programmable, bidirectional USB endpoints, including endpoint 0. See endpoint configurations. The following table 54-1 lists EP1-7 with type IN or OUT.


I did implement a dual CDC+1 generic HID which requires 5 IN-EP and 3 OUT-EP and that seems to run just fine. So I believe that I can have up to 7 IN-EP and 7 OUT-EP in parallel (+ EP0, of course).


In 54.3.14 the DEN field indicates that the module has 8 EP, but does not state whether these are single direction or not.


But then in 54.3.26 there are only four EP (0-3) listed, separated by direction. This also makes for 8 EP, but obviously only EP0IN t- EP3IN and EP0OUT - EP3OUT are available. This pattern repeats in similar registers like 54.3.35.


Since my device actually works I believe the USBHS module does have EP4-EP7 IN/OUT as well and the manual may be wrong.


Or do I miss something and the information is actually consistent?