I have issues with USB on a custom board with mk20dx256vlk10 MCU. For some time we used mk20dx256vlk7 (72MHz) chip and everything was working fine.
Later we switched to 100MHz chip. All the modules work without any issues except the USB_LDD. The symptoms are the following:
1) Connect the device to host PC
2) Receive BusSpeedDetect event
3) Never receive DeviceSetupPacket event
4) Host notices connection but can't recognize device (i.e. empty device and vendor id, etc.)
5) Disconnect device from host PC
6) Receive BusSpeedDetect event
This was tested with 2 vkl7 boards and 3 vlk10 boards using different cables and PCs.
I also tested different clock configurations without any success on mk20dx256vlk10.
I checked the references and did not find any differences in USB sections.
Also I created an empty project based on mk20dn512vlk10 PE configuration with only USB_LDD module. The results was the same - USB working on vlk7 and not working on vlk10.
Is there some important configuration I missed? Are there any hardware differences in USB modules? Is this known issue?
P.S. I use CW 10.6.