Roboard rs485 with linux and Dynamixel

[wendyandrea]

Hi, first time i post on this forum, we are trying (my team and i) to connect 26 dynamixel rx-28 servos with the rs485 in "c" with a RoBoard 100 in Linux,

all the documentations of the SDK of the Dynamixel, refers to the USB2Dynamixel, but we want to use the RS485 of the roboard, wen i compile the USB2Dynamixel SDK example, there is an error telling me that was unable to find the USB2Dynamixel and there is not explanation about the RS485 for the RoBoIO.

please help me!

[i-Bot]

The SDK for Dynamixel was designed to use the USB2Dynamixel. And like most USB2Dynamixel software uses the FTDI specific drivers ( ftdi_sio for linux, FT2xx for Windows) instead of a virtual COM port. The FTDI drivers demand an FTDI device like the USB2Dynamixel, hence your error. The RS485 port on the Roboard 100 is not driven by an FTDI device.

I don't know much about Roboards, but I guess some solutions are:
1) Use an external USB2Dynamixel on a USB port
2) Use a Roboard 110, which has an FTDI device. You would need to use COM6 and add an external MAX3443 driver controlled by TXEN.
3) Find, modify or write a new driver library which controls the Roboard 100 RS485 port and does the dynamixel protocol. This will only work up to 115K.

[wendyandrea]

thanks, we'll try the driver, i guess we could just send package of data like a serial buss with some driver like libserial right??.

[matt.stevenson]

Yes, you can just send packets through ttyS1 to control a Dynamixel chain connected to the RS485

There is an old thread on this here: http://robosavvy.com/forum/viewtopic.ph ... highlight=

In that thread Shervin Emami posted a link to his site. He wrote a C++ library for windows, which may be helpful http://www.shervinemami.co.cc/dynamixels.html

I wrote a library in Java to control a Dynamixel chain which I am using on the RoBoard. It uses the RXTX library which in turn uses libserial or something similar. I'd be happy to send you a copy of it.

[wendyandrea]

yes please! that would be helpfull, also i have been using libserial to send package with results, the problem is that at some time, there is an error that close the program, the error is:

Terminat called after thowing an instance of std:runtime_error
what(): interrumped system call
Aborted(core dumped)

i guess is something related with the bandwidth, i'm using the default of dynamixel, but i'm not sure.