Connecting Battery, Servos and Xbee to AxonII. Are the connections Right ?

[bilals]

Hi,

Some of you might know that i am building a hexapod as i seeked help several times. Its now just a matter of hours before i receive the Axon II microcontroller and the Xbee Starter Kit. As i am new to robotics i know little about it. This is why i want you guys to check if the follwing connections are right.

First of all i'd like to know if this is right:

1) I have 18 servo motors (Like the one in the picture below). Is it correct if i connect them to the pins (G5-B7 & H7-L0) in the Axon II.  Sample servo connected is shown below on pin B4.
2) The battery connection shown below.
3) Shown also is an Xbee Explorer Regulated. Can i the connect it to any of the pins (L1-L7). Below, its connected to pin L1 for power and to UART (U0) for T&R.

Note: The blue dots in the picture are used to show the end points of each line.




One thing i'd like to ask about also is:

I found this information in the Axon II datasheet:

Hardware PWM
Hardware PWM is perfect for creating a perfect high frequency squarewave without any cost to the processor. Servos using hardware PWM can only be used on 16 bit pins, while regular DC motors can be used on any PWM pin.
8-bit timer pins: G5 (T0), H6/B4 (T2)
16-bit timer pins: B5/B6/B7 (T1), E3/E4/E5 (T3), H3/H4/H5 (T4), L3/L4/L5 (T5).

Do my servos use PWM ? If yes, then does this mean that i can only connect them to the 16-bit timer pins (Only 12 of them) ? What are the timer pins used for? Do I need them for the hexapod project ?

[GWER57]

1. Yes

2. looks good

3. It looks like you made one wrong connection. Din is supposed connects to tx and Dout is supposed to connect to rx. I know it sounds wrong but it is all relative. Din means that the board is recieving the data and that means the axon must send the data (tx). Just look at admin's uart tutorial as it has good illustrations and explinations.

4. yes but they are very particular. look at the pwm tutorial.

Good luck with your project, looks exciting !

[GWER57]

3. Also, the breakout board has to be connected to 5v regulated (blue in the diagram) and ground. and not to the unregulated battery (red).

[bilals]

Thanks GWER57,i got it regarding the DIN and DOUT.

3. Also, the breakout board has to be connected to 5v regulated (blue in the diagram) and ground. and not to the unregulated battery (red).

But whats the breakout board ? Is it the Xbee Explorer Regulated ? I should connect it (GND and 5v from Xbee Regulator) to A0 for example ?

[waltr]

But whats the breakout board ? Is it the Xbee Explorer Regulated ? I should connect it (GND and 5v from Xbee Regulator) to A0 for example ?

Yes.
I'll second everyone's suggests.

[KurtEck]

3. Also, the breakout board has to be connected to 5v regulated (blue in the diagram) and ground. and not to the unregulated battery (red).

This is the way I do it as well. 

But I did ask Sparkfun if I could also pass it 6v (I meant to ask from 6v Battery) and they said it should be fine.  The reason I asked this was if sometime I put in a higher power

XBee Pro, I was not sure if the power requirement might but a strain on the 5v regulator.

Kurt

[madsci1016]

3. Also, the breakout board has to be connected to 5v regulated (blue in the diagram) and ground. and not to the unregulated battery (red).

Not true, You can connect it to unregulated, the Xbee regulated board can take up to 16V.

[Admin]

bilals, did you get this adapter to work?

According to this thread it won't . . .
http://www.societyofrobots.com/robotforum/index.php?topic=9790.0

[bilals]

Unlike the thread you've posted, my problem was being unable to receive data.
I was able to transmit data (through Axon-Xbee to the other Xbee on the robot) but not to receive.

[madsci1016]

Unlike the thread you've posted, my problem was being unable to receive data.
I was able to transmit data (through Axon-Xbee to the other Xbee on the robot) but not to receive.

That's actually the exact problem he linked too. It turns out the MIN high transmit voltage the Xbee will send to the Axon is only 2.7V, but the MIN high voltage Receive value for the Axon is 3V.  So the Axon can't receive the 1's of the data if the voltage is below 3V, which is what the Xbee can put out.

[Soeren]

Hi,

In that case, a buffer made of an NPN and a PNP (plus a few resistors) should help.

[madsci1016]

Hi,

In that case, a buffer made of an NPN and a PNP (plus a few resistors) should help.

I suggested the same on the other thread.

[KurtEck]

I also had problems with the Sparkfun adapter with the Axon2.  The funny thing is that I think it has worked OK on a Seeeduino Mega board which has the same chip... On my Axon2 robot I used an adapter from Selmaware, which had it's own voltage regulator and Buffer IC to do the voltage shifting.  They since then have discontinued selling Xbee adapter boards.  I wonder though if the one for Parallax (http://www.parallax.com/Store/Accessories/CommunicationRF/tabid/161/ProductID/664/List/0/Default.aspx?SortField=ProductName,ProductName) would do the trick.

Kurt

[KurtEck]

Quick update,

For the fun of it I did purchase two of the cheap boards from Parallax (link in previous post). I also purchased two new Xbee 1s...  Today I wired one of these up.  Note this is a DIY project as you do have to solder the connectors on... So today I tried one of these on my Axon2 based Lynxmotion Brat and it appears to work . 

If you don't want the hassle of soldering you could probably try one of these instead: http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/32401/List/0/SortField/4/ProductID/691/Default.aspx

Kurt

[Admin]

I'm reporting that the Parallax XBee SIP Adapter works on my project with the Axon.