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Discussion - Drivers / Re: FT_Write returning FT_OK but BytesWritten is 0
« on: January 21, 2020, 10:13:15 pm »
Sorry, I ended up resolving this but never posted the final results.
It turned out to be a problem with the hub IC. It was built into the CPU SOC and it would randomly lower the output voltage of the D+/D- signals sometimes so that the FTDI couldn't discern the signal. We never got the vendor to admit why. We eventually got a work around in the bios by changing the hub from xHCI to EHCI Controller. The hub had USB 3.0 ports which we weren't using and I think they were confusing the 2.0 ports by trying to negotiate sometimes? Not sure. By using the EHCI controller it forced the USB 3.0 ports off and the problem went away.
It turned out to be a problem with the hub IC. It was built into the CPU SOC and it would randomly lower the output voltage of the D+/D- signals sometimes so that the FTDI couldn't discern the signal. We never got the vendor to admit why. We eventually got a work around in the bios by changing the hub from xHCI to EHCI Controller. The hub had USB 3.0 ports which we weren't using and I think they were confusing the 2.0 ports by trying to negotiate sometimes? Not sure. By using the EHCI controller it forced the USB 3.0 ports off and the problem went away.