USB Device Issue on Cyclone V / HPS

Hello,

Please find below a description of the USB issue we are experiencing with our Cyclone V / HPS board.

To test our USB interface, we integrated the TinyUSB library into our existing firmware and enabled FreeRTOS support.

Since the Cyclone V is not natively supported, I implemented the missing functions using Altera's hwlib, which we already use in our project (source file attached).

The USB is used only in Device mode. I tested the following four configurations:

• Full-Speed with Slave mode
• Full-Speed with Simple DMA
• High-Speed with Slave mode
• High-Speed with Simple DMA

The behavior is identical in all four cases:

• Connecting our board to a Windows or Linux host is correctly detected.
• The SETUP transaction is successfully received, and the host receives the device descriptor in response.
• When the IN transfer complete interrupt is triggered, the USB controller is configured to receive a zero-length packet on OUT0. However, the USB protocol analyzer shows that the device continuously responds with NAK to this packet.
• The host retries for approximately 5 seconds, but the device keeps responding with NAK.

The register values immediately after configuring the reception of the OUT0 packet are:

• Gotgctl = 0xd00c0
• Gintsts = 0x4000020 (PTxFEmp, NPTxFEmp)
• Gdfifocfg = 0x1f802000
• Dctl = 0
• Dcfg = 0x8100001
• Dsts = 0x18702
• Doepctl0 = 0x80008000
• Doepint0 = 0
• Doeptsiz0 = 0x80000
• Grxfsiz = 0x50

After a few milliseconds, I observe that DOEPINT0.NAKINTRPT = 1, which seems to confirm that the device is sending NAKs. However, I do not understand why the OUT packet is not being accepted, since the receive FIFO is not full and both DCTL.GOUTNAKSTS = 0 and DOEPCTL0.NAKSTS = 0.