DTE vs DCE Selection using NI VISA

[pweil95]

I am working on a project that involves the use of the NI USB-232 cable, part number 778472-01, and have been having some slight troubles during setup. After installing the proper drivers and NI software such as MAX and VISA, I have been trying to figure out how to configure the wire mode as either DCE or DTE.

According to the various instructions I have found, this should be as simple as opening the hardware configuration utility, accessing a dropdown, and changing it there. However this drop down is not present, or at least anywhere that I can see. Using VISA, I can see the wire mode attribute, and can see that it is currently set as DTE, but can not seem to find a straightforward way of changing it.

My leading suspicion is that this cable does not support switching between the two, as on the datasheet (see attached, on page 9) it mentions that switching is only possible for 232/2 or 232/4 cables. I'm hoping I'm just missing something small in the software somewhere and that this cable actually has the functionality, but if not, then I will just modify my project plans slightly.

[JÞB · Accepted solution]

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@pweil95 wrote:

I am working on a project that involves the use of the NI USB-232 cable, part number 778472-01, and have been having some slight troubles during setup. After installing the proper drivers and NI software such as MAX and VISA, I have been trying to figure out how to configure the wire mode as either DCE or DTE.

According to the various instructions I have found, this should be as simple as opening the hardware configuration utility, accessing a dropdown, and changing it there. However this drop down is not present, or at least anywhere that I can see. Using VISA, I can see the wire mode attribute, and can see that it is currently set as DTE, but can not seem to find a straightforward way of changing it.

My leading suspicion is that this cable does not support switching between the two, as on the datasheet (see attached, on page 9) it mentions that switching is only possible for 232/2 or 232/4 cables. I'm hoping I'm just missing something small in the software somewhere and that this cable actually has the functionality, but if not, then I will just modify my project plans slightly.

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The difference between DTE and DCE is physical.   You can't reverse the copper with software.   Period, end of sentence.

You need a different cable assembly or a crossover adapter that matches the physical design of your endpoints.

[pweil95]

Thanks for your reply! I think that's where my confusion came from, since my intuition would be that its a physical connection, but when looking into the datasheet and other examples of NI VISA, it mentioned the ability to switch. Since it can't be switched, I will modify my plans for the cable instead, thanks for clearing it up!