I have been playing around with trying to use an Arduino Due to try to control some Robotis AX-12 servos. I am currently trying it by using an AX-12 CDS55xx Driver board by DFRobot (http://www.dfrobot.com/index.php?route=product/product&filter_name=dynamixel&product_id=579#.UUisLsrCs3g)
I am not sure if their board will try to drive the RX line at 5v or not, but I am going through a TTL Level converter chip on my Shield.
The problem I am running into is I don't believe the USARTs on the Due can run the Dynamixels at their full buss speed of 1000000.
That is, if I understand the baud rates on the Due, when I ask for a baud rate of 1000000, the actually generated baud rate is: 84000000/(n*16). Best fit n=5, so actual baud rate is: 1050000 so off by about 5%,
which is not close enough. I believe the spec for the servos is it can handle a delta of up to 3%
I believe if I wish to continue down this route, I could potentially reprogram the servos to run at a baud rate of 666666, as you can set the baud rate to 2000000/(n+1). On the Due, the closest to this would be I believe on the due to the nearest baud rate would be at 656,250 or ((656250-666666)/666666)*100=-1.56% which may work...
Suggestions? Also my quick look over the the Due code base, my impression is I may have to fiddle with the Baud rate I pass in as I think it only truncates a division of the baud into the CPU speed. It does not do any rounding...
Thanks
Kurt