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Author Topic: FT600 Drops Off Bus with Two Devices  (Read 1031 times)

timrprobocom

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FT600 Drops Off Bus with Two Devices
« on: February 10, 2022, 07:14:08 PM »

We are using an FT600 to stream incoming telemetry continuously at 100MB/sec on Ubuntu Linux 18.04.  We are required to support two such devices.   Telemetry is delivered as an 8k chunk every 81us.  We're running this on a beefy Xeon Silver server with 20 processors and 64GB RAM, with an Intel C620 host controller.  We're also trying a separate Renesas host controller.

If we run one device, we seem to be able to run without problems.  We've had sessions up to 4 hours.  If we run two devices on two separate host controllers, we've also had sessions up to 4 hours without a problem.  But if we have both devices on the same host controller, after some amount of time (sometimes 30 minutes, sometimes several hours), one of the two devices stops talking.  Occasionally, if I FT_Close the device and reopen, communications will resume, but most often, after I close the device, all further opens gets FT_DEVICE_NOT_FOUND, despite the fact that the device still exists in "lsusb".  I have to unplug and replug to resume streaming.  Our FPGA is still operational, but the FT600 is signalling that the FIFO is full  The other device continues to operate correctly.

It's not clear what we can do to chase this down.  In order to drop off the bus like that, it seems like it has to be a USB protocol problem.  Do you have reports of problems running multiple FT600 with high loads?
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FTDI Community

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Re: FT600 Drops Off Bus with Two Devices
« Reply #1 on: February 11, 2022, 02:28:50 PM »

Hi,

we haven't had any reports about multiple FT600s. But recently a customer reported this issue with one FT600 which breaks down when a second process has started in the system.

does the problem occur when something else has started in your system or is it completely random?

this application note might be of help to you: https://ftdichip.com/wp-content/uploads/2020/07/AN_386-FTDI-FT600-Maximize-Performance.pdf

Best Regards

FTDI Community
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timrprobocom

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Re: FT600 Drops Off Bus with Two Devices
« Reply #2 on: February 19, 2022, 06:45:27 AM »

I wanted to offer some followup on this.

We discovered a minor setup-and-hold violation in our FPGA.  Clearing that up seems to have eliminated this problem.  That seems like a good ending, but it is uncomfortable to us that such a problem could cause the FT600 to drop off the bus.  We will continue to do testing.

Thanks for the response.
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