Servo Control

whitelancer

To whoever can help me,

I am an engineer doing reserach on micro robots that resemble nature. I am using a Javelin Stamp to control five servo motors that need to move to a specific position at a certain time. The Stamp needs to communicate with a servo control and give it six byte commands to move the motors. I was wondering what command would best be suited for the project. Thank you for anyone that can provide help.

Sincerely,
Jon

Peter Verkaik

You need to provide more info.
Which servo controller?
Apparently you have this info, otherwise how do you know
that the servo commands are six bytes?

If you don't have decided on a servo controller,
there is this one:
http://www.parallax.com/detail.asp?product_id=910-28023

There is already a javelin class for this servo controller.

regards peter

whitelancer

Thanks for getting back so quick...

I am using a Pololu Micro Serial Servo Controller seen at the website posted below. Connected are five Pico Servo Motors from the same company. Let me know if you need any more info.

Sincerely,

http://www.pololu.com/products/pololu/0207/

Peter Verkaik

I skipped through the manual
http://www.pololu.com/products/pololu/0207/ssc03a_guide.pdf

and this is quite straightforward and well documented regarding the protocols.
For an example how to setup a class for this controller,
take a look at the psc class (parallax servo controller).

regards peter

Parasar

Thank you for the files. They have been a great help in providing a starting point for the programming.

Sincerely,

Jon

Parasar

To anyone that can help,

I have attached programs that I am trying to use to test my Pololu servo controller. They are based on the example programs and I am hoping for help with the details. Thank you.

Sincerely,

whitelancer

Yes I am also working on something very similar and I am curious how you send out data to a the servo controller.

Thanks!

Peter Verkaik

I put the pololu_msc.java in package stamp.peripheral.servo.pololu
(create folder lib/stamp/peripheral/servo/pololu)

Now both files compile

regards peter

whitelancer

Thanks for the help,

I am using the starter kit and trying to send out the data to the servo controller via pin 0, however the controller is not registring that anyting is being recieved. I have checked the connections and believe that it is somthing with the test program. I was hoping someone could check the program that is posted above or if if it is something with my connections.

Thanks!

Peter Verkaik

I simplified your test program.
Now it merely reads the used servo numbers and the green led should flash to identify the servo numbers.
(default servo numbers is 0-7 and the led flashes 1 time, see manual)
The reading is repeated every 3 seconds.

regards peter

whitelancer

Thanks for the help...

I am now trying to check to see if I am reciveing or even sending data correctly. I was hoping that this program would do the trick; however, I am running into some problems. Please let me know if you can help. Thanks again.

Sincerely,

Peter Verkaik

The manual states the baudrates must be 2000-40000 so your 1200 is pointless.
I suggest to stick to 9600, at this baudrate the javelin throughput (about 10kbits/s) equals
the baudrate, meaning the uart buffer is emptied at the same rate as you can fill it.

Did my test program make the led flash as it is supposed to do according to the manual page 8?

If not, try Uart.invert instead of Uart.dontInvert and see if that works.

regards peter

whitelancer

Thanks for the help,

The test program is not making the led flash. I played around with the connections, the baud rate, and anything else I could think of. Do you think that it is a hardware problem with the servo controller?

Sincerely

Peter Verkaik

You must have the following connections:
javelin transmit pin to servo board logic level serial input
javelin gnd to servo board gnd AND power gnd (all gnd's must be tied together)

Do not power the servo board from the javelin vdd pin.

Do you have it setup that way?

regards peter

whitelancer

I am using the Javelin Starter Kit with board and I'm a little confused on what you mean by tying all the gnds together. Thanks for walking me through this.

Sincerely

Peter Verkaik

Normally the servo's are powered by their own power supply.
Connect that power supply to the servo board pins labelled
VIN and GND (left lower corner on picture at page 2 of manual)

Power the javelin using another power supply. Connect that power
supply as instructed in the javelin manual.

Now connect 2 wires from javelin board to servo board.
One wire goes from transmit pin (pin0 in javelin test code)
to the servo board pin labelled Logic level serial input.
The second wire goes from GND at the javelin board to
GND at the servo board.

Then try the test program again. Change the Uart.dontInvert setting if
it does not work.

Edit: just noted there is a seperate servo power connection on the servo board.
So you may power the servo board at VIN connection using the same power supply
as used by the javelin.

regards peter

whitelancer

Yep,

I needed to connect the gnds to each other and the code was dontInvert. Thank you so much. I really appreciate the time and effort that you spent. Nowhere else is anyone able to provide the support found here. Thank you again.

Sincerely,
Jon

Peter Verkaik

Now that you have the connections right,
you can test your original program.

regards peter