controlling servos for hexapods using avr (ATMEGA16/128)

Hexapod Robots

controlling servos for hexapods using avr (ATMEGA16/128)

Postby trisonics » Sun Aug 30, 2009 8:46 am

Hey guys ,
1)Can any give me links to some tutorials for controlling servos using avr ATMEGA series microcontrl.
2)Also how to do PWM using avr - does it invlove using RTClock IC ?
3)Last - i need some tutorials on inverse kinematics for 3DOF hexapod.
trisonics
 
Posts: 3
Joined: Thu Aug 20, 2009 5:35 pm

Re: controlling servos for hexapods using avr (ATMEGA16/128)

Postby Demmo » Tue Sep 01, 2009 2:00 pm

Hi and welcome to the forum :)

ad1) i'm not sure if there is any exact tutorial for controlling servos using AVRs because the general thing is how to control a servo position (PWM) and after that is how to do this with (any kind of) microcontroller... anyway, remember that Google is your friend ;) uhmm.. one of links returned by search engine:http://mil.ufl.edu/~achamber/servoPWMwCodeVision.html

The question is: What do you want to do? ATmega will be good for smaller amount of servos but if you want to control a 3DOF hexapod with 18 servos ATmega probably will be too weak... I think 16MIPS@16MHz can't handle IK and other calculations in proper time and refresh rate of servo positions will be poor.. but maybe I'm wrong ;)
You can use a servo controller like p.Brain and only send commands or use faster microcontroller...

ad2) AVRs don't need RTC for PWM generation. Most (if not all) microcontrollers use internal timers/counters to generate hardware PWM or you can do it but software but it's not recommended.

ad3) once again.. Google is your friend ;)
http://www.google.com -> type: great inverse kinematics -> search.. click ;) http://www.learnaboutrobots.com/inverseKinematics.htm Not clearly enough? http://www.google.com -> type... :lol:
:lol: ok, sorry.. i know it was a little bit cruel but it really seems you haven't even try to search for any info... :D
Demmo
btw. sorry for my english :P I should educate more ;) :lol:
Demmo
 
Posts: 36
Joined: Wed Jun 18, 2008 5:46 am
Location: Gliwice, Poland

Re: controlling servos for hexapods using avr (ATMEGA16/128)

Postby trisonics » Tue Sep 01, 2009 5:30 pm

So will lpc2xxx microcontrollers do the job which r 32bit mcus.

I have 2 choices here :
[url]
http://www.standardics.nxp.com/products ... 2.lpc2103/[/url]

and

http://www.standardics.nxp.com/products/lpc2000/lpc214x/

Both - series of mcus work at higher frequencies ; around 60-70Mhz.
trisonics
 
Posts: 3
Joined: Thu Aug 20, 2009 5:35 pm

Re: controlling servos for hexapods using avr (ATMEGA16/128)

Postby Demmo » Tue Sep 01, 2009 6:18 pm

much much better :) :D

lpc214x offers USB etc so price will be higher because of functionality unuseful in this kind of application... BUT.. max. memory (flash & sram) sizes are smaller in lpc210x so you have to ask someone (i.e. Matt :D ) about typical code size and sram usage... unfortunately i have no idea how much of them is needed :)
Demmo
btw. sorry for my english :P I should educate more ;) :lol:
Demmo
 
Posts: 36
Joined: Wed Jun 18, 2008 5:46 am
Location: Gliwice, Poland


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