Assembling Brat biped with servos

Lynxmotion Legged Robots
1

Hello,

I’ve assembled the mechanics of the Biped Brat. Can you confirm if it is required centering in mid position the servos “before” assembling them?

Can you also point me out to an “how to” tutorial of doing this operation using FlowBotic Studio?

Thanks
Regards
Riccardo

2

Hi Riccardo,

Here are answers to your questions:

Yes, the servomotors should be centered (position = 1500 µs) before the horns are attached to the brackets.

There are two main ways:

  1. Open FBS and load up the Sequencer project. With it, connect to your powered SSC-32/SSC-32U that is on your Biped Brat and activate all required channels. Then, press the CENTER ALL button at the top to center all the servomotors. Make sure to keep yours fingers/face/etc. clear of the robot for this steps, as it will move suddenly.
  2. Use Lynxterm (mentioned in our previous reply to you) to do pretty much the same thing as option #1. If some of the servomotors are not perfectly aligned (might be 1-2 degrees off or even a bit more), you can use the SSC-32’s calibration feature to rectify this.

First, center all servomotors with the horn disconnected from the brackets.
Then, connect the horn to the brackets.
Re-center again and look at each joint to see if they are centered properly.
Open-up Lynxterm and connect to your SSC-32. Follow the steps in the image below to calibrate:

Lynxterm - Calibration.png
Lynxterm - Calibration.png1185×475 24.6 KB

Sincerely,

3

Hi Sebastien,

Thanks for your reply.

I pretty much completed construction of the Brat. Following is a link to a photo on my google drive showing the Brat
drive.google.com/file/d/0B3ATzl … sp=sharing

My final goal will be to install a sensor, send data to an Http Api and receive back some commands.

I have a Genuino 101 board. Do you have a tutorial or some instruction on how to connect with the SSC32u? I tried to connect the TX on the Genuino with the RX on the SSC32u (ground pin included) but it doesn’t seems to work and there is a blinking red light on the SSC32u.

I’m not sure if I can send command through the Genuino to the SSC32u using Flowbotics Studio or do I need to use the Arduino ide?

If I connect the XBee that I received with the kit to the SSC32u and the BlueTooth module to the laptop, can I control the Brat sending commands directly?

Thanks
Regards
Riccardo

4

Hi Riccardo,

That’s quite a few questions you have there! Lets go through each of the one by one:

That looks great! You should probably make some videos of it moving, too! :slight_smile:

This would be awesome! Are you going to have the HTTP service running on your Arduino 101 or separate (and connected by Bluetooth or some other wireless technology)?

You can see the connections required on page 21 of the SSC-32U manual. As you mentioned, TX/RX/GND connections are required. It should be mentioned that while the Genuino 101 is able to tolerate 5 V DC inputs, it works at 3.3 V DC and therefore its output may not work for the SSC-32U, which expects 5 V DC signals for digital highs. You can use something like the RB-Spa-879 to convert between the SSC-32U’s 5 V signals and the Arduino 101’s 3.3 V signals.

If you wish to use the Genuino for other things, than yes, the Arduino IDE would be required. You can also use it as a passthrough. The example for SoftwareSerial does just that, actually! You can find it in the Arduino IDE under File -> Examples -> SoftwareSerial -> SoftwareSerial Example. Of course, you will need to change the baud rate and pins to match your setup. The SSC-32U uses 9600 baud rate by default, but you can change it using the Baud button or programmatically. Check page 34-35 for details.

Yes, you can. This is one of the main ways to connect the SSC-32U to a computer or FlowBotics Studio.

Also, if you wish to know how to send commands to the SSC-32U using your Arduino board, you can check the manual on pages 24-26 for details on the basic commands.

Sincerely,

5

The Http Api will be hosted on a remote machine. Locally I probably need a client library that can make http requests and pool an Atom feed for commands at a specified interval.

I like the idea to start developing the remote http server, connecting to it from my laptop with a little process that then interact with the Brat using the Xbee without wasting any more time with the electronicss. But unfortunately I don’t think that the Xbee that I received in the kit (Droids SAS XBee - DTE Serial Board (DB9)) is compatible with the SSC32u that you sent me as a replace of the old SSC32…

I can probably buy a different Xbee like the Digi 1mW XBee Transceiver Module (Wire Antennae). I can probably also bui a voltage converter and try to use the Genuino. But it looks an overcomplicated solution and also there is no space left to put the second board on the Brat.
Maybe I can buy a BotBoarduino board and do all the job with one board. With the BotBoarduino can I use Flow Botics Studio to implement a client program (send events, polling for commands) and control the servos all in one?

6

Hi,

Here are answers to your questions and comments (inline):

That sounds like a good idea. You should be able to find many different examples online of doing client-type connections from Arduino using the board you have.

Yes, that can certainly make it work. You can possibly focus on creating a simple interface layer to the electronics and keep all the complex logic outside the embedded electronics and into your web server/controller.

Yes, this board would unfortunately not be compatible directly. That being said, you can simply place an XBee board directly on the SSC-32U instead, since it has its own socket near the USB port.

It may be simpler to indeed just stick to using a Bee-socket compatible board on the SSC-32U directly.

Well, you could do that with FlowBotics Studio whether you use the SSC-32U (with a XBee compatible board on it) or the BotBoarduino. The only really difference will be how much processing you do on the Brat directly and in the FBS app you’ll be making.

The fun (and difficult!) part of this and most robotics projects is that there is always half a dozen ways of doing something well!

Good luck with your project.

Sincerely,

7

Hi Sebastien,

I would like to buy an XBee compatible board and try to control the Brat sending serial commands.
Can you please confirm which board is compatible with the SSC32U?

I found this one on the website but it’s not available at the moment and I’m not sure if I can connect it directly on the SSC32U
robotshop.com/uk/droids-sas- … board.html

Thanks
Regards
Riccardo

8

Hi Riccardo,

The RB-Dro-01 is a XBee carrier board that allows a computer to have access by USB to the XBee module. Similarly, the SSC-32U has a XBee socket that can be used to connect a wireless module.
The typical setup is a RB-Lyn-851 (which is a RB-Lyn-850/SSC-32U with a RB-Dfr-95 XBee Bluetooth 2.0 module).
You would then pair to that module (pairing code is most likely 1234 or 0000) using Bluetooth from your computer. Most modern computers have Bluetooth integrated. If it is now your case, you can use a USB dongle to connect, such as RB-Dfr-309.

Sincerely,