On the fly half step/microstepping with L6208?

[lutzliebers]

Posted on April 06, 2004 at 15:48

On the fly half step/microstepping with L6208?

[lutzliebers]

Posted on May 17, 2011 at 10:17

Hi, I am designing a two axis telescope drive based on steppers

and L6208. The edge conditions of this application are:

- fast positionning in rectascension (hour axis) and declination

- smooth sideral tracking (with an angular speed half as fast as

the hour pointer of a clock). Typical tracking speed is 20 to

50 half steps / second (so there should be sufficiant CPU time

left for controlling such an operation)

The idea is to provide a fast ''star-hopping/go-to'' in half steps,

while doing the sideral tracking of the hour axis in micro-stepping

mode.

After having referenced an absolute sky/home position, in the course

of a sky watching session multiple switching between those basic

modes of operation should be possible without heavy loosing/falsifying

steps/position.

The micro-controller I favourize is a 16 bit Fujitsu MB90F543 just

for the reason of being familiar with. It contains programmable

pulse outputs with might be used for PWM purposes thus replacing

two additional D/A converters for defining the rectified, 90 degree

phase shifted sine wave shapes at both V-ref inputs.

Question: is there any application existing that contains programmable

mode switching between half step/microstep driving? What aspects

like internal phasing of the L6208 have to be respected?

Many thanks in advance for your appreciated reply, Lutz

[lutzliebers]

Posted on May 17, 2011 at 10:17

Hi Tanio,

thanks a lot for kindly offering me your mentioned paper.

I sent two requests to you via this ST email service but

maybe they got stuck. Nevertheless I ´m interested to

get this doc.

Please send it directly to me:

mailto:[e-mail]

Many thanks in advance, Lutz

[gaetano]

Posted on May 17, 2011 at 10:17

Hi Lutz,

I'm sorry but no apply ready to help you with your job.

Neverthless, I own a paper that explains in great details how to manage the microstepper driving mode using the L6208 driver (included the generation of sin profiles according with the phasing of the driver) and a general purpose micro (similar what you already know).

Probably giving a look to this document, it would't be so difficult to get what you want with a little brainstorming.

After all the half drive can be seen as a microstepping with less micro-steps...

Please, give me your e-mail so I can contact you privately.

Regards,

Gaetano