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Author Topic: Controlling servos -> Axon  (Read 5015 times)

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Offline CanabotsTopic starter

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Controlling servos -> Axon
« on: May 07, 2009, 06:41:49 PM »
Hey Guys.

I'm trying to make my servo turn for a specified amount of time, then turn in the opposite direction for the same amount of time. I am using the Axon.

Here is my code sofar:

Code: [Select]
void scan(void)
{
int i=0;
int j=5000;
long int wheel_left=500;

for(i=0;i<j*500;i++)
{
wheel_left=850;
}

for(i=j*500;i>j*499;i--)
{
wheel_left=500;
}

wheel_left(wheel_left);
delay_ms(20);
}

For some reason, the servo will move in pulses until it reaches a certain point, then it just stays there...

Any input or ideas as to what might be wrong with my code?
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Offline Admin

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Re: Controlling servos -> Axon
« Reply #1 on: May 07, 2009, 06:46:42 PM »
Quote
Any input or ideas as to what might be wrong with my code?

first, this is impossible:
int j=5000;

int only goes to 255 . . . make it a long int . . .

same for i

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #2 on: May 07, 2009, 07:04:46 PM »
So I changed it. I removed the variable "j" since I didn't end up needing it and changed "i" to a long int.

Here's the code:
Code: [Select]
void scan(void)
{
long int i=0;

long int wheel_left=500;

for(i=0;i<65535;i++)
{
wheel_left=850;
}

for(i=65535;i>65535;i--)
{
wheel_left=500;
}

wheel_left(wheel_left);
delay_ms(20);
}

But it does the same as before...
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Offline Admin

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Re: Controlling servos -> Axon
« Reply #3 on: May 08, 2009, 12:25:23 AM »
Code: [Select]
for(i=65535;i>65535;i--)
should be

Code: [Select]
for(i=65535;i>0;i--)

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #4 on: May 08, 2009, 04:34:24 AM »
Code: [Select]
for(i=65535;i>65535;i--)
should be

Code: [Select]
for(i=65535;i>0;i--)

I think that makes it worst  :-[ Now, the servo doesn't move or do anything at all, as if no commands are being sent.

Thanks for all your help sofar Admin
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Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #5 on: May 08, 2009, 05:20:07 AM »
Instead of using the variable wheel_left, I decided to try commanding the servos with "servo(PORTx,Pin,position)"

This made it work...like the first post.
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Offline Admin

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Re: Controlling servos -> Axon
« Reply #6 on: May 08, 2009, 07:19:03 AM »
Throw in some rprintf statements and see what it's doing with hyperterminal.

Also, check your voltages.

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #7 on: May 08, 2009, 07:44:35 AM »
I'm fairly certain it's not voltage, since when I use the Roborealm software for controlling servos, they respond with no problems. I'll check anyway.

I will add a couple rprintf statements, though don't expect to hear from me until next week, as I am busy this weekend.

Thanks! :)
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Offline chelmi

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Re: Controlling servos -> Axon
« Reply #8 on: May 08, 2009, 09:13:40 AM »
I think the problem is that you update the servo position at the end of the scanning loops. You must update it inside the loop.
Can you post the code you are running now ? I'm a bit lost with your modification :)

BTW:

Quote
Any input or ideas as to what might be wrong with my code?

first, this is impossible:
int j=5000;

int only goes to 255 . . . make it a long int . . .

same for i
int a 16 bits, so it's between -32768 and 32767.
char are 8 bits, long int are 32 bits and long long int are 64bits. Assuming you are using AVR GCC / Win AVR (and probably other compilers but I'm not sure).

Chelmi

Offline Webbot

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Re: Controlling servos -> Axon
« Reply #9 on: May 08, 2009, 01:07:02 PM »
Try changing both your variables from 'long' to 'unsigned long'
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Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #10 on: May 09, 2009, 01:07:29 PM »
I think the problem is that you update the servo position at the end of the scanning loops. You must update it inside the loop.
Can you post the code you are running now ? I'm a bit lost with your modification :)

I think you may be on to something. I modified the code to update servo positions at the end of each FOR loop, though no way of determining if it's the problem until I can test it later. Though I think that may be it. :)

This is my change in the servo code:

instead of doing this:
Code: [Select]
wheel_left(850);I would use this:
Code: [Select]
servo(PORTE,6,850);
It is currently irrelevant since I'm using the wheel_left commands again :P
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Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #11 on: May 11, 2009, 02:07:29 PM »
Ok, so I changed and tested my code, but it still does the same thing. For some reason my rprintf statement isn't working either...
Code: [Select]
rprintf("Servo_Position=%d%d\r\n", wheel_left);
All It shows is "System Warming up" and "Initialization Complete" which is odd since I only modded it a bit from what I was using in a previous test...

Admin, what type of code did you use for those ERP and movement demos where only the arms would move and such? I just wanna see a sample so I can tell maybe what I'm doing wrong.
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Re: Controlling servos -> Axon
« Reply #12 on: May 11, 2009, 02:13:42 PM »
Quote
All It shows is "System Warming up" and "Initialization Complete" which is odd since I only modded it a bit from what I was using in a previous test...
Sounds like a low battery problem . . .

Quote
Admin, what type of code did you use for those ERP and movement demos where only the arms would move and such? I just wanna see a sample so I can tell maybe what I'm doing wrong.
I used the SoR Biped Engine with the latest released Axon code.

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #13 on: May 11, 2009, 03:48:59 PM »
Just measured voltage again, looks like the level is dangerously close to the minimum at 5.6V. I'm going to swap them out and get back to you.
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Re: Controlling servos -> Axon
« Reply #14 on: May 11, 2009, 05:45:26 PM »
Yea, with any microcontroller, if you say to yourself 'what the heck it was just working, nothing much changed, and now suddenly its acting all strange?!', that typically means low battery. :P

Took me years to figure that out . . .

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #15 on: May 11, 2009, 07:29:55 PM »
Ok, changed the batteries.

And for some reason it doesn't work...

I think I'm going to first try starting a completely new project, completely fresh, and ad my code to control.c This way, if it's an issue with the other code, then my problem's fixed.

Otherwise, I'll keep debugging the old one.
« Last Edit: May 11, 2009, 08:07:28 PM by Canabots »
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Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #16 on: May 13, 2009, 05:34:32 AM »
Alright! Started  a new project for this some older code in AVR Studio and it is now back to working like it used to ;D which means that Hyperterminal works again!

At first, it looks like my servo controlling code would always stop at the 800 value. So I changed my code a little. Now instead of one subroutine named "scan"I have 2 named "scan1" and "scan2". Upon doing this, I think I discovered the problem. I have to declare "wheel_left(wheel_left)" inside the FOR loops, which fixes it at only one value.

As for why it moves in pulses, I don't know. Though when observing the Hyperterminal, after about a second (I think), it stops, and says "System Starting Up" and then "Initialize". Then it displays values again. When I try the default Photovore code, the transfer is continuous, so I know it's something wrong with my code. Any ideas?

So now I guess I just have to figure out how to make it not stop at the first FOR loop. Does anyone know how?

Here is my code with the 2 subroutines.
Code: [Select]
void scan2(void)
{

long unsigned int i=0;

long unsigned int wheel_left=500;

for(i=0;i<500;i++)
{
wheel_left=350;
wheel_left(wheel_left);
delay_ms(10);
rprintf("Wheel_Value=%d%d\r\n",wheel_left);
}


}

void scan1(void)
{

long unsigned int i=0;

long unsigned int wheel_left=500;

for(i=0;i<500;i++)
{
wheel_left=900;
wheel_left(wheel_left);
delay_ms(10);
rprintf("Wheel_Value=%d%d\r\n",wheel_left);
}


}

Also, here is what void control(void) looks like

Code: [Select]
void control(void)
{
scan2();
scan1();

}
« Last Edit: May 13, 2009, 06:05:13 AM by Canabots »
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Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #17 on: May 13, 2009, 02:26:53 PM »
So to make sure I could really control a servo using the Axon, I just did the following test.

Code: [Select]
PORT_ON(PORTA,7);
delay_ms(2);
PORT_OFF(PORTA,7);
delay_ms(20);

This did make the servo turn all the way.

But there is still the annoying pulse thing! It moves the servo in pulses, with the exact same timing as the System start up and initialization in Hyperterm.
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Offline Admin

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Re: Controlling servos -> Axon
« Reply #18 on: May 13, 2009, 03:31:01 PM »
Quote
   for(i=0;i<500;i++)
      {
      wheel_left=350;
      wheel_left(wheel_left);
      delay_ms(10);
      rprintf("Wheel_Value=%d%d\r\n",wheel_left);
      }

I see in your code that you are allowing only 10ms between servo pulses. Some servos will spass out if you do that, so increase that delay to 20ms. What servo are you using?

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #19 on: May 13, 2009, 04:08:33 PM »
Yes, I've noticed that and changed the ms pulse to 20. I was just trying out different pulse values and forgot to change it back :P

As for the servos, they are HS-311 servos
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Re: Controlling servos -> Axon
« Reply #20 on: May 13, 2009, 06:01:00 PM »
I'm kinda stuck on this . . .

Get out an oscilloscope and take measurements of the PWM.

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #21 on: May 13, 2009, 06:14:36 PM »
I don't have an oscilloscope...unless you mean the Axon :P But I don't know how to run my program at the same time as the O-scope program...

I decided to try using a system very similar to that you used on your old ERP robot with the $50 board. Sofar it's gotten rid of the wierd  movement of the servos in pulses, though all the servos do now are twitch  :D  Still working on it.

Code in my .h file (for the servo motions)
Code: [Select]
long int i=0;
long int j=0;

void servo1(signed int position)
{

PORT_ON(PORTA,7);
delay_ms(position);
PORT_OFF(PORTA,7);

}
void servo2(signed int position)
{
PORT_ON(PORTE,6);
delay_ms(position);
PORT_OFF(PORTE,6);
}

void scan(void)
{
for(j=0;j<500;j++)
{
for(i=500;i>0;i++)
{
servo1(2);
servo2(1);
delay_ms(20);
}
}
for(j=0;j<500;j++)
{
for(i=500;i>0;i++)
{
servo1(1);
servo2(2);
delay_ms(20);
}
}
}


In control.c
Code: [Select]
void control(void)
{

while(1)
{
scan();
}
}

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Offline Admin

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Re: Controlling servos -> Axon
« Reply #22 on: May 13, 2009, 06:38:58 PM »
An idea . . . rprintf any and all variables (especially the ones that change) in your FOR loop.

Also, maybe you mentioned this before but, what is your battery voltage and type?

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #23 on: May 13, 2009, 06:42:32 PM »
My batteries are Alkaline batteries.

I just popped them in and their voltage is at 6V.

So rprintf i and j and all that?

Thanks
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Re: Controlling servos -> Axon
« Reply #24 on: May 13, 2009, 07:44:51 PM »
My batteries are Alkaline batteries.
Dude thats your problem (well plus your earlier code mistakes)! Alkaline just can't supply enough current.

Go by some NiMH or NiCad batteries and move on, lol. :P
« Last Edit: May 13, 2009, 07:46:07 PM by Admin »

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #25 on: May 13, 2009, 07:48:19 PM »
If it can't supply enough current, why do the servos work fine with the servo controller? Unless it uses less power because of the pc connection...


Also, what type of current rating should I looks for? I suppose I'd plan to use this for around 10 servos atleast (I plan on making a Quadruped robot).
« Last Edit: May 13, 2009, 08:11:34 PM by Canabots »
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Re: Controlling servos -> Axon
« Reply #26 on: May 13, 2009, 08:22:24 PM »
If it can't supply enough current, why do the servos work fine with the servo controller?
hmmmm good point lol . . .

Quote
Also, what type of current rating should I looks for? I suppose I'd plan to use this for around 10 servos atleast (I plan on making a Quadruped robot).
allow for 0.5A per HS-311 servo, then just look up the max current rating of the servo

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #27 on: May 13, 2009, 08:27:04 PM »
If it can't supply enough current, why do the servos work fine with the servo controller?
hmmmm good point lol . . .

So does this mean that the battery is the problem? Or still just some stupid error in the code that everyone has missed? Lol I'm becoming totally confused :D

Thanks
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Re: Controlling servos -> Axon
« Reply #28 on: May 13, 2009, 08:28:48 PM »
Can you explain exactly what you servos are doing wrong in more detail? (assuming it's changed from the first post)

Offline CanabotsTopic starter

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Re: Controlling servos -> Axon
« Reply #29 on: May 14, 2009, 09:47:54 AM »
Ok
Can you explain exactly what you servos are doing wrong in more detail? (assuming it's changed from the first post)

With the latest code I posted the servos will "twitch" continuously. There are no breaks while twitching. The motion is going side-to-side, always at the same rythm. It also seems like the motor changes direction each twitch.

I'm going to try some testing without the FOR loops to see if they are the problem.
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