Hi,
I am looking for some help about the possibility to control Lynxmotion Smart Servo HT1 using an OpenCM485 EXP coupled with an OpnCM9.04 board (Arduino-based board).
I built a robot having an OpenCM 9.04 board as the microcontroller, coupled with an OpenCM485 EXP expansion board acting as power hub and communication board to drive a set of Dynamixel AX-12a and XL-320 servos.
I need to replace some of the servos with something having more torque, and I was exploring the possibility to use the Lynxmotion LSS HT1.
At the moment I would be able to replace only part of the servo and not the entire set (also because the XL-320 have a different size and I cannot replace them anyway).
However, I have several doubts about the wiring/communication.
The Lynxmotion LSS servo uses TTL full duplex asynchronous serial with 4-pins molex connectors (pinout: Rx | Vcc | GND | Tx).
The OpenCM 485 EXP has several 4-pins molex connectors for RS-485 (pinout GND | VDD | DATA+ | DATA-) plus some other 3-pins connectors for TTL (pinout GND | VDD | DATA).
I am definitely not an expert of the matter so I am not able to understand if there is a way to drive the LSS servos with this board.
Obviously a simple connection cable with the proper pin wiring should not be the case and I imagine that some kind of RS-485 to TTL converter (to use the 4-pins connections) is required.
Can someone help me understand if there is a suitable adapter board that can be used to this purpose?
Alternatively, is there an Arduino shield suitable for driving both Lyxnmotion LSS and Dynamixel AX-12a/XL-320?
The OpenCM 485 EXP has several 4-pins molex connectors for RS-485
As you can see, the four pin connector is RS485, which is not compatible with the LSS’s communication method. The three pin headers on the OpenCM board are evidently also not compatible.
Can someone help me understand if there is a suitable adapter board that can be used to this purpose?
It won’t be easy to use the same communication bus to control both Dynamixel and LSS servos as they are quite different from each other. You’d likely need two serial ports: one to control Dynamixel, and the other for LSS. Not sure if the OpenCM 9.04 board has two serial lines - you’d need to check.
Alternatively, is there an Arduino shield suitable for driving both Lyxnmotion LSS and Dynamixel AX-12a/XL-320?
The LSS Adapter is shield-compatible, however you’d need to see which pins are used for communication, and then see if there’s a Dynamixel shield which can stack on top of that. However, this won’t be straightforward since power also needs to be considered.
We have not had many users want to use the LSS with Dynamixel, especially since both the protocol and mounting are very different.
Care to share what the project is and how many servos it has at the moment?
You’d likely need two serial ports: one to control Dynamixel, and the other for LSS. Not sure if the OpenCM 9.04 board has two serial lines - you’d need to check.
Unfortunately not, at least not in the way they would be needed in this case (the board has 3 serial lines, however 2 of them are dedicated to driving the Dynamixels via the 485 EXP and the 3rd one I am using to connect the board to my computer that I use for sending commands via serial).
The LSS Adapter is shield-compatible, however you’d need to see which pins are used for communication, and then see if there’s a Dynamixel shield which can stack on top of that. However, this won’t be straightforward since power also needs to be considered.
This could be an option, I could use some wires to create a dedicated connection. Powering the board would probably require a separate power source. I need to make up my mind on this as right now the 485 EXP board acts bot as a communication board and as a power hub for the servos and the other board.
Care to share what the project is and how many servos it has at the moment?
A biped robot made of 22 servos, 10 of which are for the legs.
The problem actually lies in there, the AX-12a servos work well for the upper body but unfortunately the overall weight is higher than expected (the robot is custom made with 3D printed parts). In the end, the lower limbs stand a static pose but when I try to make some kind of leg movement the needed torque is more that what the servos can provide. I was therefore looking for some stronger servos to replace the leg motors, however keeping the upper part.
I’ll probably will end in redesigning the whole upper body to something lighter, or change the full set of servos.
