FDC3260 Serial Communications Not Working

We have just taken delivery of an FDC3260 for a robot control application. We can successfully control the motor drives via the RC Interface and also via USB with the Roborun Utility. However for our application we had intended to use the RS232 interface and we don't seem to be able to make it work.

Is there anything weird and wonderful required to make the RS232 interface work? Normally we use MDC2460 controllers and they just work out of the box with RS232.

In order to test it independently we have made a simple 3 wire (RX, TX, GND) harness to connect to the D-type connector. Using an oscilloscope we can see the data passing along the wire in to the RX pin on the D-type. However the echo on the TX pin on the D-type is not as expected. We are a just seeing a weak ~0.3V wave at about the right time.

Any help that any one can offer would be greatly appreciated :-)

It should work exactly the same way.

Can you confirm your wiring? It sounds like TX and RX may be switched and something got turned around when you moved from the 15-Pin port to the 25-Pin port, but there is almost no way of knowing.

If you could post more about what you are trying to communicate values from and how you have it wired, it would be very helpful to me in my trouble shooting. Right now, I don't have much to go on other than you made it work with another controller that has a different IO port on it.

Thanks for getting back to me. Apologies for the delay in replying we are offsite doing customer trials with our robot and our internet coverage is patchy.

If it should work in exactly the same way then I think we most likely have a failed serial port. Can we return the unit to Roboteq for diagnosis / repair?

I'm certain that the problem is not crossed RX and TX wires on the RS232. We have tried both orientations anyway and neither worked.

Happy to share circuit diagrams with you via email if that helps.

Yes, the wiring diagram and the configuration profile of the controller would be very helpful if you could post them.

You should also check the result of the ~RSBR command. The interface might need to be inverted.

Okay will send my drawings and profile to This email address is being protected from spambots. You need JavaScript enabled to view it.