Jump to content

Making USB-8451 work with PXI running LabVIEW RT / Phar Lap ETS

Recommended Posts


I have a problem here. Hope I can get some help for a solution.

The task at-hand is to use an NI USB-8451 to communicate with a device over I2C. This would have been trivial if it wasn’t for the fact that the USB-8451 is connected to a PXI controller running LabVIEW Real-Time OS (Phar Lap ETS) and not a Windows PC.

I haven’t chosen the hardware combination personally and the person who did just assumed they would work together. And I did too… I mean, it's NI's eco system! Just download the NI-845x Driver Software from NI’s webpage, install it on my PC and then install whatever software needed on the controller through MAX. Easy right?

But no. It wasn't that easy.

So I wonder:

(1) Has anyone had any success controlling the NI USB-8451 from anything but a Windows PC? And if so… how?? The PXI system finds the USB-8451 and lists is as a USB VISA raw device but the supplied vi’s/drivers cannot be executed on the controller.

(2) Since what I want to do is actually very little (just writing a couple of bytes once to the I2C device) I have started to toying with the idea of recording the USB traffic from the Windows laptop somehow via Wireshark and then replaying it on the PXI system… has anyone had any success doing something like that?

(3) And finally. If it is impossible to get the USB-8451 to work with my PXI system, is there some other I2C hardware that is known to do? I’m getting the impression that NI only has this USB device apart from implementing the I2C protocol on a dedicated FPGA and that seems a little too much.

Sorry for the long post. Getting a little desperate here. Deadline approaching.

I'm running LabVIEW 2019 SP1 by the way and the controller is a PXIe-8821 if that makes any difference.


Link to post
Share on other sites

At this point, I would probably go a slightly different route.  You could get an Arduino or Raspberry and program them to do the I2C communications for you.  In the RT system, you can just communicate the data through a serial port.  Another option I have been tempted to go with is to use a SC18IM700IPW, which is a I2C-UART chip.  Again, you just have to use a serial port to talk to it.  But this would be more hardware design than the other option.

  • Like 1
Link to post
Share on other sites

Adding to crossrulz suggestion.  If you do want simple I2C or SPI, using an Arduino is a great solution in LabVIEW.  NI has their LINX toolkit, which downloads a known set of firmware to the Arduino, and then in LabVIEW you have the LINX palette which basically tells the microcontroller to execute some set of steps.  These commands are just serial commands, and when plugged into USB should appear as a normal VISA device in LabVIEW.  I don't have a pharlap system to test with but with other remote devices I've used they just get enumerated when they are plugged in.

I personally have not used pharlap much and am unaware of the difficulties getting that hardware working on it.

  • Like 2
Link to post
Share on other sites

Thanks for quick answers.

I was afraid changing hardware would be the answer. Doing that isn't that easy either as the hardware configuration is quite fixed at the moment.

My current "temporary" solution is to use a Windows PC connected directly to the USB device running a looped LabVIEW *.vi which constantly writes i2c to the device every second or so. This works.

I will look into other neater solutions as soon as I get the time. I promise to post an update here if I figure out anything useful.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.