Part Number: TUSB4041I
I have implemented the TUSB4041I on my PCB with 3 permanently connected devices which are externally powered. The Hub has an EEPROM connected for configuration. It receives an external reset pulse after power-up.
The first 2 devices (ports 2 and 3) connect reliably to Windows 10 via the hub but the 3rd device (an ATSAM3X8E-AU on port 4) does not. It always shows "Unknown USB Device (Device Descriptor Request Failed)" in device manager. This device is connected with reversed polarity USB pairs which has been accounted for in the EEPROM programming.
I have taken an oscilloscope screen grab that appears to show successful USB High Speed chirps and high-speed termination being applied but the device will still not appear correctly under windows.
I can share the eeprom listing and schematic via private message.
Is your third device functioning as a Host or device? Is USB OTG enabled on your third device?
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In reply to Malik Barton57:
The microcontroller is functioning as a device.
I have since got it to to appear as a USB device by forcing it into bootloader mode via the serial programming interface.
It is quite unreliable and appears to conflict with a LAN7850 USB2.0 ethernet bridge on the same pcb but separate connection back to seperate USB2.0 port on the host pc. By conflict I mean sometimes both devices appear under device manager and sometimes they give "Unknown USB Device (Device Descriptor Request Failed)". Once the microcontroller stops appearing, it needs to be forced into bootloader mode to start appearing again. It then works for a couple of power cycles then has problems again.The ethernet bridge seems to be found on the USB more often when the microcontroller is not appearing. I have not yet pinned down the sequence of events to make it work/not work. It is difficult to separate USB hub problems from the usb device problems in this case.
I have previously implemented both the LAN7850 and SAM3X8E seperately on other pcbs without problems. The introduction of the permanently connected hub on this project seems to have brought up the issue.
I'm wondering if it is to do with the sequence of taking the ICs out of reset ie usb hub first then devices or devices then usb hub and any time delays between them. I am also thinking of the USB 5V detection that all these devices (SAM8X3E, FT232H, FT4232H, LAN7850) have and whether it is pulled high permanently or driven from the hub, or in the case of the LAN7850 supplied from the host.
Do you have any recommendations around sequencing devices out of reset or USB 5V detection for permanently connected USB hubs/peripherals?
In reply to user4928306:
I would recommend that you bring the USB Hub out of reset before the peripherals. If you have complete control of each device separately, try having each devices connect one at a time by controlling USB 5V detection or Vbus. A USB data connection should not be initiated by a peripheral until this signal is seen. Having the USB peripherals always see USB 5V detection or Vbus may cause some state machine issue internal to the peripherals themselves.
I recommend using USBTree or USBview software to aid in debugging your system. They will allow for you to see the USB descriptors once enumerated or see any addition errors on the USB bus. Can you probe DP and DM once you have entered the failure mode and devices, at device connection (Vbus goes high for permanently connected devices)?
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