Missing ACK on USB OUT Transactions

[JacobBerggreen]

My team is having some issues with missing ACKs on USB OUT transactions.

Some info on our system:

* The MCU is LPC5528

* SDK version is 26.03.00.

* For call to USB_DeviceInit, we supply kUSB_ControllerLpcIp3511Fs0 as the first parameter (controllerId) so we're using USB full speed.

It's hard to say much about patterns. What we can state is:

* When we send a lot of messages over USB, once in a while an OUT transaction is missing the ACK. We've caught this with an Ellisys USB analyser. We can see the missing OUT, then 3 retries from the PC and then a USB reset.

* It happens rarely. We set up a script repeating the same simple USB message (target just returns some data, no heavy computing etc.). Sometimes it takes a few iterations, other times thousands of iterations, before the error happens.

We'd like to know if this is a known issue or perhaps there are some tricks to debugging it.