Help with RS485 to a Micro SSC?

Support Servo controllers and servos
1

I’m pulling my hair out trying to figure this out. Hopefully someone can help!

I’m trying to hook up 3 items:

  1. Sparkfun USB to RS485 converter ( sparkfun.com/products/9822 )

then via a single twisted pair to:

  1. Sparkfun Transceiver Breakout - RS485 ( sparkfun.com/products/10124 )

then to a:

  1. Pololu Micro Serial Servo Controller ( pololu.com/product/207 ).

I’m a bit new to this but I’ve studied the spec sheets and schematics but can’t figure out what’s what on the Transceiver Breakout. Here’s my best guess. Can anyone help me sort this out?

2

With some help on another forum I was able to come up with this wiring arrangement. Does this look right?

3

Hello.

Your connections seem reasonable, but I am not familiar with the SparkFun Transceiver Breakout RS-485, so I cannot say for sure. If you have an oscilloscope, you could try looking at the output of the transceiver to see if it looks correct. Alternatively, you might try using a USB-to-Serial Adapter instead.

Additionally, please note that the Serial Servo Controller expects a 5V signal, so you might also consider using a logic level shifter if your signals are at 3.3V.

By the way, if you are just trying to control the servo controller from USB, you might consider the newer Maestro USB Servo Controllers, which are better in almost every way.

-Brandon

4

According to the specs for the RS485 Breakout Board, it should be “Interoperable with +5.0V logic”. So hopefully no logic level shifter should be necessary.

5

As I said in my previous post, I am not familiar with the SparkFun RS-485 Breakout Board, however I suspect “Interoperable with +5.0V logic” means that it can accept 5V signals. Whether a separate device will work with the 3.3V signals from the breakout board will depend on the particular device.

-Brandon