OpenServo.com Forum Index OpenServo.com
Discussion of the OpenServo project
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Starting with openservo

 
Post new topic   Reply to topic    OpenServo.com Forum Index -> Hardware
View previous topic :: View next topic  
Author Message
mog123



Joined: 07 Jun 2009
Posts: 12
Location: Poland

PostPosted: Sun Jun 07, 2009 5:38 pm    Post subject: Starting with openservo Reply with quote

Hi, I am a newbie with digital servos, I only operated on analog ones. I'd like to start with openservo, because it's much much cheaper than getting commercial digital servo's. I have some programming skills with AVR (eg.24 channel servo controller). Ok, enough of the introductions.
My questions is:
What do I need to get started with openservo? Do/Why do I need a "servo programmer"? I don't know how TWI or I2C works, should I need to learn it beforehand? Which version of the open servo is "available" to make at home? I saw that v3 has a 4 layer pcb, which is out of the question.
For all your replies,
thank you ver much.
Back to top
View user's profile Send private message
jharvey
co-admin


Joined: 15 Mar 2009
Posts: 361
Location: Maine USA

PostPosted: Mon Jun 08, 2009 10:05 am    Post subject: Reply with quote

I'm also quite new to this. Here's my take on it.

You need a programmer if you assemble it. This is because there isn't a boot loaded installed from the factory. After you upload your first firmware, you can program it with out a special programmer.

If you purchase your open servo board, it's my understanding that robotfuzz will upload that first firmware. This allows you to take it and run with it.

You'll need to modify a servo removing the guts, and replacing them with the OSV3 guts. Shouldn't be that hard, couple wires to solder, and a little nibbling may be required to get the connector to come out.

If you want to go the DIY approach, which is my goal, I've got a pile of extra boards. I only need like 10 or so, and I ordered something like 160. This got the cost down to a couple bucks each. I'm willing to sell those if your interested.

I2C is TWI. Basically I2C is Philips name, and TWI is generic. It's a data bus that allows you to kind of daisy change several devices off one bus with one acting as master. I understand a reasonable limit is 16 servos per I2C bus, however you might want to plan for less devices per bus.

More about I2C here.

http://en.wikipedia.org/wiki/IēC
Back to top
View user's profile Send private message Visit poster's website
mog123



Joined: 07 Jun 2009
Posts: 12
Location: Poland

PostPosted: Mon Jun 08, 2009 1:54 pm    Post subject: Reply with quote

Well I do have a STK500v2 standard programmer (USBasp). Is it enough or do I need some kind of USB/I2C adapter?
I'd like to make my own boards if that's possible (with atmega8's).

So basically it's like this:

1. do your pcb
2. program the controller with an AVR programmer(like stk500?)
3. solder the controller onto the board.
4. Replace the PID on the servo with the openservo
5. Write your servocontroller using openservo commands

Is that all?
Back to top
View user's profile Send private message
jharvey
co-admin


Joined: 15 Mar 2009
Posts: 361
Location: Maine USA

PostPosted: Mon Jun 08, 2009 8:37 pm    Post subject: Reply with quote

I think a lot of that sounds about right. I'd guess your board can program the chip.

I'm curios, does anyone know if the dragon can program it? Or perhaps there is a better programmer these days?

http://www.atmel.com/dyn/Products/tools_card.asp?tool_id=3891
Back to top
View user's profile Send private message Visit poster's website
mog123



Joined: 07 Jun 2009
Posts: 12
Location: Poland

PostPosted: Tue Jun 09, 2009 8:18 am    Post subject: Reply with quote

The dragon is just a module for the programmer, you need to check what kind of programmer do you have.
Back to top
View user's profile Send private message
jharvey
co-admin


Joined: 15 Mar 2009
Posts: 361
Location: Maine USA

PostPosted: Tue Jun 09, 2009 9:38 am    Post subject: Reply with quote

The Dragon is a USB powered device that can directly do ISP, HVSP, JTAG and a couple other programming methods. Or at least that's according to this link.

http://support.atmel.no/knowledgebase/avrstudiohelp/mergedProjects/AVRDragon/AVRDragon.htm

Some things I believe it can't do are ICE, and a couple debug techniques. I think it also doesn't lend its self all that well to batch programming. It's really a one device at a time kind of programmer. However it's low cost, about $50usd.

I believe OSV3 is programmed via HVSP, so this should upload the initial firmware just fine. I'll of course have to make an adapter cable, but that's not a big deal.
Back to top
View user's profile Send private message Visit poster's website
ginge
Site Admin


Joined: 14 Jan 2006
Posts: 1030
Location: Manchester, UK

PostPosted: Tue Jun 09, 2009 9:26 pm    Post subject: Reply with quote

OpenServo v2 and above are all programmed using the low voltage programming method. This is done through SPI and can even be flashed using a PC parallel port.

There are more links on these subjects than I can post here, but this one will give you a good idea on where to start asking questions

http://www.openservo.com/StepByStep

Cheers
_________________
http://www.headfuzz.co.uk/
http://www.robotfuzz.co.uk/
Back to top
View user's profile Send private message Send e-mail Visit poster's website Yahoo Messenger MSN Messenger
BasicFox



Joined: 15 Mar 2009
Posts: 59
Location: Belgium

PostPosted: Fri Jun 12, 2009 11:58 am    Post subject: Reply with quote

The parallel programmer didn't work for me... don't know why exactly but i've made the ponyprog serial programmer and that does the job (also a lot faster i think).
The voltage regulator can be sampled and make sure u put a working transistor in it :p spend a lot of time searching why it didn't worked the first time till i measured out my transistor...

PonyProg:
http://www.lancos.com/prog.html
Schematic:
http://www.lancos.com/e2p/siprog_base.png

Also u have to enter the fuses with checkboxes, a 0 stands for checked and a 1 stands for unchecked
Back to top
View user's profile Send private message Visit poster's website MSN Messenger
FireBALL



Joined: 24 Jul 2009
Posts: 28

PostPosted: Sat Aug 29, 2009 2:46 pm    Post subject: Reply with quote

this one works for me with avrdude

Code:
http://www.sparkfun.com/commerce/product_info.php?products_id=9231
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    OpenServo.com Forum Index -> Hardware All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group