USB-8451problem

[gunking]

I have been playing with 8451 and suddenly today it couldn't work properly even with the code which worked well yesterday.

the error messages is either "reference invalid" or " wrong address". with MAX in USB device, it shows the "working properly", but when I hit the VISA test panel, it never show next step. I am wondering if something is wrong in hardware...

Anybody could give me a hint? thanks

[jon_mcbee]

Make sure your task is referencing the correct Device ID number.  If you have multiple devices connected and unplug one there is no gaurantee that when you plug it back in the Device ID will stay the same.

[gunking]

it became that worked sometime and didn't work sometime...

[gunking]

when it refused to work, three error message showed up in sequency:

1. " the slave didn't acknowledge an address+direction byte transmitted by I2C master....

2, try to run second time, error : " timeout expired...."

3 try  to run third time, error " device reference is invalid..."

after that, try to run and got same error...Restart MAX and the device didn't show up in "device" even with it plugged in and light on

unplug the USB divice and plug in again, in MAX, it showed up. but sometime it worked and sometime it repeated above errors again...

what can be wrong? thanks a lot for your help 

[mr_]

gunking--

Which version of the NI-845x driver are you using?  The reason I am asking is because different versions of LabVIEW are compatabile with different versions of the NI-845x driver.  I have linked a National Instruments KnowledgeBase that indicates the driver compatability information.

KnowledgeBase 4P8FTABB: LabVIEW Compatibility With NI-845x Drivers

Also, do you get an error number when you are experiencing this issue?  A common error I have seen involving "device reference is invalid" is error -301706.  There is another KnowledgeBase that explains this error and indicates that you should create an alias for your NI USB-8451.

KnowledgeBase 3V9ECCQW: Why Do I Get Error -301706 When Trying to Connect to My USB-8451?

If you are interested in how to create an alias, I have linked another KnowledgeBase that will step you through the process.

KnowledgeBase 3VMGBS5N: How Do I Access My 8451 From LabVIEW?

Let me know how this works for you!

Cheers!

[gunking]

Hi, Thank you very much for your detail reply...

I am using 7.0, the driver is oldest one

now I figured out when the error happened.

I was trying to connect another micro-controller device and then there were tow I2C devices, EPROM and the micro-controller. The error showed up when I ran the VI reading EPROM. to fix it, It seems that I have to change the USB 8451 device name in MAX and reboot my PC. 

I noticed that the LED on 8451 is flashing when it is working. while it stays on when error happened.

Thanks again for your help...

[gunking]

but it is working now...just couldn't communicate with the micro, saying "slave didn't acknowledge the address+direction..."

[mr_]

gunking--

That's great to hear!  So everything is working properly now?

Cheers!

[gunking]

No yet.. it still couldn't talk with mirco, but it was able to talk with EPROM...trying to figure out

[gunking]

working now...dig into the micro code and figured out the correct address

t