Post by thread:Servo Code Not Working

part 0 755 bytes content-type:application/x-unknown-content-type-asm_auto_file;I'v been modifying Peter Baine's servo controller code so I could control a single servo on a pic16c84 running at 4 MHz. (I wanted it to be as simple as possible) But for some reason, it doesn't work. All the servo does is that it points in a certain direction and stays there. Even if I change the delay for the pulse duration the servo won't move a bit. Could someone take a little look at the program and see if something's missing? Attached to this message is the small program. Thank you very much, Jean-Francois Joly Content-Type: application/x-unknown-content-type-asm_auto_file; name="srvctrl2.asm" Content-Disposition: inline; filename="srvctrl2.asm" Attachment converted: wonderland:srvctrl2.asm (????/----) (0000E6F0)

Hi Jean, I have had a quick look at your modified version of my code. You seem to have misunderstood the timing requirements of the servos. Each servo you want to control must have a pulse of between 1 and 2 ms with a duty cycle of 18 to 20 ms. your duty cycle timer must take account of the duration of the control pulse. I.E. after the counter for the pulse has expired you must also add the rest of the 2ms wait before entering the duty cycle timer. If you like I will Modify the code and post it back to you. Cheers Peter Baines..... ==================================== Remember .... Every Silver Lining Has It's Cloud ==================================== ---------- : From: Jean-Francois Joly <spam_OUTjolyalTakeThisOuTCAPITALNET.COM> : To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU : Subject: Servo Code Not Working : Date: Sunday, December 21, 1997 7:05 PM : : Hello everyone, : : I'v been modifying Peter Baine's servo controller code so I could : control a single servo on a pic16c84 running at 4 MHz. (I wanted it to : be as simple as possible) But for some reason, it doesn't work. All the : servo does is that it points in a certain direction and stays there. : Even if I change the delay for the pulse duration the servo won't move a : bit. : : Could someone take a little look at the program and see if something's : missing? Attached to this message is the small program. : : Thank you very much, : Jean-Francois Joly : :

part 0 891 bytes content-type:application/octet-stream; name="srvctrl2.asm"Peter .......... ==================================== Remember .... Every Silver Lining Has It's Cloud ==================================== : : I'v been modifying Peter Baine's servo controller code so I could : control a single servo on a pic16c84 running at 4 MHz. (I wanted it to : be as simple as possible) But for some reason, it doesn't work. All the : servo does is that it points in a certain direction and stays there. : Even if I change the delay for the pulse duration the servo won't move a : bit. : : Could someone take a little look at the program and see if something's : missing? Attached to this message is the small program. : Content-Type: application/octet-stream; name="srvctrl2.asm" Content-Description: srvctrl2.asm () Content-Disposition: attachment; filename="srvctrl2.asm" Attachment converted: wonderland:srvctrl2.asm (????/----) (0000E753)

Someone wrote: > Each servo you want to control must have a pulse of between 1 and 2 ms with a duty > cycle of 18 to 20 ms. Your duty cycle timer must take account of the duration of > the control pulse. I.E. after the counter for the pulse has expired you must also add > the rest of the 2ms wait before entering the duty cycle timer. In my experience the repetition frequency is of little importance when testing servos. I have used, for some years, a program that pulses a pin on the Centronics port of a PC for such tests. This repeats at the "timer-tick" interrupt rate, which is 18.6 ticks/sec, or a 54 mSec period. This is a perfectly adequate arrangement. You can speed up the timer-tick if you want to. The idea is to write a small TSR, to which the timer-tick interrupt is redirected 18.6 times per second. The TSR generates the 1-2 msec pulse. It gets its pulse-width data from a Basic or other program which runs in the normal way; this program takes its input from the keyboard, and passes it to the TSR. In fact, instead of connecting a servo to the Centronics port, why not connect the transmitter output stage to it, and use the PC as the transmitter? Then you can program it in Basic. It's a bit bulky to carry around of course, especially as you also need a Honda motor-generator to power it all with. John Blackburn.

Hi, I have uploaded code on my website that controls 7 servos and is written for the 16c84. It can be improved but it does work as stands. If you are interested. Just go into Robotic Projects http://webhome.idirect.com/~bine Bye for Now Eric At 08:23 AM 12/22/97 -0000, you wrote: >Hi Jean, > I have had a quick look at your modified version of my code. You seem to {Quote hidden}>have misunderstood the timing requirements of the servos. Each servo you >want to control must have a pulse of between 1 and 2 ms with a duty cycle >of 18 to 20 ms. your duty cycle timer must take account of the duration of >the control pulse. I.E. after the counter for the pulse has expired you >must also add the rest of the 2ms wait before entering the duty cycle >timer. If you like I will Modify the code and post it back to you. > >Cheers Peter Baines..... > >==================================== >Remember .... Every Silver Lining >Has It's Cloud >==================================== > >---------- >: From: Jean-Francois Joly <jolyalKILLspamCAPITALNET.COM> >: To: .....PICLISTKILLspam.....MITVMA.MIT.EDU >: Subject: Servo Code Not Working >: Date: Sunday, December 21, 1997 7:05 PM >: >: Hello everyone, >: >: I'v been modifying Peter Baine's servo controller code so I could >: control a single servo on a pic16c84 running at 4 MHz. (I wanted it to >: be as simple as possible) But for some reason, it doesn't work. All the >: servo does is that it points in a certain direction and stays there. >: Even if I change the delay for the pulse duration the servo won't move a >: bit. >: >: Could someone take a little look at the program and see if something's >: missing? Attached to this message is the small program. >: >: Thank you very much, >: Jean-Francois Joly >: >: >