USB to Serial Port Adapter

[David-Baratheon]

Hi, my laptop doesn't have a serial port.

If I wish to connect to some NI hardware using RS-232, RS-485, CANBUS etc, will I get any problems using a USB to serial adapter?

When I was programming PIC microcontrollers, we were told not to use the adapters to program the PIC. I found this a little confusing as the signal coming from the adapter should be identical to what would come from a serial port. I am not sure what the reason is.

Are there any known issues using a USB to serial adapter with NI hardware (specifically the sbRIO-9651 Reference Carrier that I am using and also just in general) or should I be fine to use it?

[Spex]

You shouldn't expect to have any issues between the SOM and a USB RS232 adapter.  The SOM refernece carrier includes a fully compliant RS232 transceiver, so it functions at RS232 line levels, not just the 0-5V TTL that some low cost USB adapters use.

I have seen low cost USB RS232 adapters that don't fully comply with RS232 specifications, and that may be why some other folks recommended not interfacing between PIC and a USB adapter.  The NI USB-232 is the adapter I always use (I work at NI). It is on the expensive side for USB RS232 adapters, but I know that NI has built a port that handles the corners cases of RS232 correctly.

Cheers,

[SnowMule · Accepted solution]

I've got a box of NI USB-232's that no longer function.  Not sure if it's a ground loop or something with the signals through it, but ... yeah, they don't last real long in my experience.  (This was years ago, i've sent a bunch back, don't know if improvements have been made since then.)

IOGear GUC-232A and SILabs CP2102/MAX3232's work well for me; never had a problem with those.  Anything FTDI is solid, beware of counterfeit chips with that manufacturer.

SILabs has an HID-UART chip available (CP2110) that works well on machines that have restricted driver-installing permissions. 

[David-Baratheon]

Thanks, I think I'll get a FTDI  US232R-100  ADAPTOR CABLE, USB TO RS232, 100CM from farnell and see how I get on with it