Errors when using multiple USB-8473 devices

[Marcus_Anderson]

I am trying to put together an application that uses five USB-8473 devices simultaneously on one PC. I can't seem to get more than two of them running without getting error -1074388956 (object handle invalid). Any two of them will run together, but when I go from two devices to three, I get the error every time. I have gone through and made sure that the object handles I am providing to ncReadNetMult are the same ones generated by ncOpen. Is there some limit to the number of these devices that can be run at the same time on one PC?

It is not a USB issue (though they are all on the same powered hub) because I am only writing 4 frames/sec on each device and get the same issue without any modules attached.

I need to run five at a time so I can talk to five modules with the same address at the same time.

[Kareem_W.]

Marcus,

Can you please clarify your comments regarding the USB hub? Specifically why you believe the hub is not part of the issue? I looked into the spec for the USB 8473 and these devices are rated at 250mA and 5VDC per module. Can you please check the rating of your hub? If you are trying to run 5 modules simultaneously, you will need the hub to output 1250mA to power all 5 modules. One of the common current output ratings is 500mA per hub - thus your ability to run only 2 modules.

One way to eliminate the hub as the root cause is to try to connect multiple modules directly to your computer. I checked on my system and found that each of my 7 USB ports is rated at 500mA each. To check on your computer simply go to the Device Manager and expand USB Controllers. This will let you know how many internal "hubs" are on your system. When you right click on a hub, select "Properties", and click the "Power" tab, you will see the current rating of the ports assigned to that internal hub. If you have 3 (or more) available ports that meet the power requirements, then you should be able to test with three (or more) modules to see if the issue is present without the external powered hub.

To me it sounds as though your hardware requires more current than the hub can supply.

[Marcus_Anderson]

Thanks for the reply. I figured it out - and feel dumb now :). It was a timing issue. I was trying to read from the CAN device before the configuration completed. I was OK with one or two because the configuration of the CAN devices was fairly quick. When I went beyond three CAN devices, the combined configuration took just long enough that I was attempting my first read before the configuration completed.