To have much better control of the speed of your modified servo check-out this variable-speed mod: http://www.seattlerobotics.org/encoder/200009/S3003C.html That has a link to a simple circuit to check-out your servo mod using a 555 timer: http://www.uoguelph.ca/~antoon/gadgets/servo3.htm And to answer the question you actually asked :-> Some examples of servo control with 16F84 here: http://home.planet.nl/~robot/nn2000/nn20002.html#Z80 http://www.havingasoftware.nl/robots/servo/servo.htm Hope that helps. I haven't actually done any of this - have just collected a good set of notes preparing to do it. ----- Original Message ----- From: "Dale Botkin" To: Sent: Monday, December 24, 2001 7:12 AM Subject: Re: [PIC]: Servo code & robots > I've done both in C, but not assembly... if you'd like to see the servo > C code from my first attempt (warning:ugly, amateur C code!) you can see > it at https://www.botkin.org/dale. There is a .LST file that has the C > and ASM code in the same listing, if that helps. > > What I do is set up a regular interrupt using TMR0, usually around 1ms. > In the interrupt service routine I increment a counter. When the counter > hits the refresh interval of 20ms (or a little longer), I generate a pulse > with its period determined by the value of a variable. So all I have to > do is make that variable represent the position (or speed, in your case) > desired for the servo, and let the ISR do the work. > > I have long suspected that the servo will hit max speed with a pretty > small offset in an application like yours. I have done some poking around > inside Futaba and Airtronics servos with a 'scope, it's pretty > interesting. Been meaning to use a couple for a robot drive for a year or > so now, but I keep getting side--tracked on other projects. Maybe on '02. > > By the way, if anyone has not seen it yet, the /TAB BOOKS BUILD YOUR OWN > ROBOT KIT/ is available in the US at Barnes & Noble. Awesome deal!! > Designed by Myke Predko & Ben Wirz, two names that should be very familiar > to anyone on this list. It's a complete PIC controlled robot kit in a > box, with a socket for a Basic STAMP II and Parallax App Mods. Price is > $60 and B&N had 20% off when I got one for my 16 year old son. The web > site at http://www.tabrobotkit.com/ has complete source listings and > schematics, so it's a hack-friendly platform. My *only* wish is that the > wheels were big enough for carpet use. Anyway, #3 Son will be opening it > some time today or tomorrow, I'll have more info on it then. I just hope > someone took my blatant hints and got one for me too! > > Dale > -- > "Curiosity is the very basis of education and if you tell me that > curiosity killed the cat, I say only the cat died nobly." > - Arnold Edinborough > > > On Mon, 24 Dec 2001, Prince Anamalech wrote: > > > > > Hello fellow PICSter's > > > > I am new to the pic scene but have gained sufficient knowledge to get me through so far! > > i am currently building a robot using a PIC16F84 . I am using two hacked servos for the motors, and am hoping to use two > > ultrasonic transducers (40Khz) to detect obstacles. > > I have hacked the servo's using a transistor bridge (making it think it is always in the centre position). I am trying to > > test out the servos by writing some assembly code with mplab, but i am having no success. > > I have connected the servo's control wire to a pic pin. PINS A.0 and A.1. Left and Right respectively. > > i have tried manipulating some code on the piclist archive but with no success. > > COULD anyone please help me out with some assembly code PLEASE? > > also does anyone have any ideas or schem's/code to help me out with my ultrasonic's?? > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body