(The Questions are at the end )
I am using the XEM6310 to transfer data from the PC to the FPGA and then towards I/O pins as well as data from I/O pins towards the FPGA, towards the PC.
(Windows 7 PC)
Using BT pipes in both direction. The SDRAM is used as (4 separate) FiFo's
Speed varies between 5 Mbytes/second up to 80 Mbytes/second.
Sometimes it is needed to place the xem6310 in an electrically shielded box with a usb3.0 feed through connector through the box wall.
When using a setup with two high quality usb3 cables (1 meter and 20 cm) sometimes USB communication errors occur. After a few minutes or a few hours.
(I do use the latest Opal-kelly xem6310 drivers, libraties etc. )
When this occurs the XEM6310 does NOT react to USB anymore. The FPGA still seems to run.
A USB analyzer indicates unexpected transactions before communcation stops. It looks like the FX3 is getting 'confused' and stops responding.
Disconnecting and connecting the cable results in an enumaration request that is not seen by the FX3. Disconnecting the power is the only option.
(I also tested with only the XEM6310 attached, no other devices)
In older FX3 Cypress forums, the FX3 USB was sensitive to noise generated on the FX3-FPGA interface during data transfers and other noise sources.
I assume the cable-extension does result in higher susceptibility to noise for the (weaker?) USB3 signals.
1) Assuming the setup mentioned what things can be done to minimize 'digita; noise.
Longer block pipe-transfers, shorter block pipe-transfers,
short delays between block pipe-transfers ?
2) Force usb2.0 by software ?
For some uses it would be enough to force the device towards high-speed, instead of superspeed. One way to force this is to use an usb2.0 cable in between. Is there a way using the frontpanel API to force a device to use high-speed when using a usb3.0 cable ?
(I did notice that on one or two PC's when connecting the XEM6310 you sometimes (once or twice a month) get a powersurge message after which the XEM6310 presents itself at high speed)
I would be glad with any comments