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Instrument Control (GPIB, Serial, VISA, IVI)

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FT230X USB Serial device is not detected as COM Port in PXI RT 8183

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We have connected USB Serial devices to the two USB Ports available in the PXI RT 8183 Controller. It is getting detected as USB0 Raw and not as Serial COM Port. What is the way to detect this device as COM Port to interface the device in LabVIEW using NI-VISA.


Chassy : PXI 1036

Controller : PXI RT 8183

OS : NI Realtime Pharlap ETS 13.1

LabVIEW Software - LabVIEW 2014

PXI Software : LabVIEW RT 14.0, NI-Serial RT 14.0.0



Please let me know incase of more information.



Hameed Ibrahim

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Message 1 of 7
Accepted by hameedkdnl

There is no way! The Phar Lap ETS system only comes with USB drivers for Mass Storage devices and USB TMC devices (which use technically a very similar protocol specification to the USB Mass Storage Class, but with an IEEE488.2 protocol implementation on top of the bulk data channel.


There are no USB COMM class drivers for the NI Phar Lap ETS system and to make matters worse, although it doesn't change anything in reality for you, are the FTDI chips not supporting the USB COMM class specification but use their own proprietary USB protocol.

Rolf Kalbermatter
Averna BV
Message 2 of 7

Thanks  for the clarifications.

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Can we use USB to RS232 converter to connect the USB device to the NI PXI 8430?


Will this work?

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Message 4 of 7

That very much depends on the device but most likely not. Your device would need to support USB host capability so that the USB adapter can be connected to it. USB may look like both sides are the same but it isn’t. The host side enumerates the device(s) connected to it, determines their device class, VID and PID, and optionel serial number from the generic device profile request and then makes that device class available to the system. Your device is simply a USB FTDI proprietary device class and waits for the host to chat to it and connect it with a driver that can talk USB FTDI slang. Your USB RS-232 adapter does the same, USB FTDi or standard USB COMM slang doesn’t matter, and they both will sit there and wait until hell freezes over but never start to talk together. 

If you really are desperate for this device to work with this controller, your cheapest.solution in terms of hardware cost would be probably to use a Raspberry Pi or similar to connect your device to. It may take a little Linux command shell tinkering to get the FTDI device recognized on boot up. Then you need to connect the FTDi uart with the real uart on the Raspi through a software loopback connection and then connect the real uart to the PXI. But note that the Raspi uart on the extension header is 3.3V TTL level while your PXI RS-232 is +-12v level, so you would need also a level shifter between those two!

Rolf Kalbermatter
Averna BV
Message 5 of 7

How to check the TTL Voltage level of NI serial card. We are using PXI 8430/8. Is all available NI PXI Serial cards are +/- 12V TTL?

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Message 6 of 7

If it says RS-232 you have to assume that it is using proper RS-232 (or V24) signalling levels, which means yes it uses +-12V nominally (but accepts +-3V to +-15V on the receiving side as the standard requires). It means that your 3.3V TTL on the Raspberry Pi (or Arduino or whatever) input would simply be destroyed if directly connected together. Also the space or idle value on RS-232 side is actually +3 to 15V while it is 0V on the TTL side, so the logic polarity is actually inversed between RS-232 and TTL.


Simple boards like this can be used to do the level translation properly. Trying to create your own circuitry would definitely cost more as you usually can't buy the parts in the same volumes yourself.

Rolf Kalbermatter
Averna BV
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