Dynamixel bus monitor
Dynamixel bus monitor
by Fritzoid
Sat Apr 17, 2010 3:16 pm
Debugging problems in Bioloid hardware and software can be a challenge. Often you need to see the packets and their responses from the dynamixels. Some of you savvy roboteers my have used RoboPlus terminal in manage mode to send commands and view their responses. A few of you might even know about the bootloader's MON command which does about the same thing. The problem with both of these functions is that they take a long time to format and transmit the messages back to the PC. They also can't help you in Play mode.
What you really want is some kind of all-purpose sniffer for the dynamixel bus. Here's what I came up with.
Take your USB2Dynamixel (in TTL mode) and wire it to an available connector on the robot. The last servo on an arm or the unused connector on the top of the CM-510 are convienient places to attach it. Now start up a serial port monitor. I use the HHD Free Serial Port Monitor (no link). After the monitor is attached and configured to the correct serial port you need to start up RoboPlus terminal. This will probably come up connected to the wrong port so disconnect if you are already connected. Then reconfigure the connection to use the USB2Dynamixel port number at 1Mb (1000000 bps).
You can run another terminal session on the regular port number at 56Kb or you can use any of the other RoboPlus software at the same time. Alternatively you can just press the buttons on the controller to initiate a test. In any event, all the traffic on the dynamixel bus will be displayed on the terminal session. Of course it will be largely readable in RoboPlus, that's why I use the port monitor. This displays the data in hexadecimal without any formatting, just what I needed.
The result is a real-time dynamixel bus monitor using just the stuff lying on my desk.
When your done, remember to end the terminal session BEFORE you end the port monitor.
What you really want is some kind of all-purpose sniffer for the dynamixel bus. Here's what I came up with.
Take your USB2Dynamixel (in TTL mode) and wire it to an available connector on the robot. The last servo on an arm or the unused connector on the top of the CM-510 are convienient places to attach it. Now start up a serial port monitor. I use the HHD Free Serial Port Monitor (no link). After the monitor is attached and configured to the correct serial port you need to start up RoboPlus terminal. This will probably come up connected to the wrong port so disconnect if you are already connected. Then reconfigure the connection to use the USB2Dynamixel port number at 1Mb (1000000 bps).
You can run another terminal session on the regular port number at 56Kb or you can use any of the other RoboPlus software at the same time. Alternatively you can just press the buttons on the controller to initiate a test. In any event, all the traffic on the dynamixel bus will be displayed on the terminal session. Of course it will be largely readable in RoboPlus, that's why I use the port monitor. This displays the data in hexadecimal without any formatting, just what I needed.
The result is a real-time dynamixel bus monitor using just the stuff lying on my desk.
When your done, remember to end the terminal session BEFORE you end the port monitor.
by MikeG
Sat Apr 17, 2010 10:41 pm
Yeah, I'm not following either.
Serial port monitors are great for logging I/O and figuring out what is being passed. You can only monitor the software/hardware connected to a particular port.
I built a simple open source C# project that helps build instruction packets. You kinda have to have an idea what you're doing though.
http://www.agaverobotics.com/services/d ... fault.aspx
Serial port monitors are great for logging I/O and figuring out what is being passed. You can only monitor the software/hardware connected to a particular port.
I built a simple open source C# project that helps build instruction packets. You kinda have to have an idea what you're doing though.
http://www.agaverobotics.com/services/d ... fault.aspx
by Fritzoid
Mon Apr 19, 2010 11:11 am
OK here's the big picture. Your using two terminal sessions on two different USB ports. One using the normal path to the robot. USB to dongle (not USB2Dynamixel) to serial cable to link plug on CM-510. This one runs at 56Kb. The other terminal session takes another path straight to the dynamixel bus. USB to USB2Dynamixel to any attached dynamixel device. This sessiojn runs at 1Mb. If you stick a port monitor on this session you can see and log the actual dynamixel traffic in hexadecimal and at full speed.
by Fritzoid
Mon Apr 19, 2010 6:47 pm
Yes that's it, however there's a certain synergy between the terminal program and the port monitor that you may not be appreciating. The port monitor can't choose the speed or direct the data. The RoboPlus terminal program can't display in hexadecimal or log the data. But together they work beautifully.