Hi John,

Thanks for the tip.

If I understand you correctly, if I make a loop and read from a status port
n times before writing the next step I should get an interval of n
microseconds.

Neat.

I am not planning to use the port to drive the coils directly. Thanks for
the warning.
Pramod

----- Original Message -----
From: "John De Villiers" <bbj@PLZ.CO.ZA>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, December 28, 2000 4:15 PM
Subject: Re: [EE]:writing data to IBM PC parallel port to drive stepper


> dont use delay - its too slow
>
> I think the trick was to do a port read ( one of the status bits or
> something equially arbitary ). Those take 1 microsecond
>
> The fastest i was able to go was about 50 us before the stepper started
> skipping beats. It also depends if youre half stepping or full stepping. I
> also suggest you use a tranny of some sort as the pc par port can let out
> its smoke if you draw too much from it. I used normal TIP31's as i had a
> whole box full of them.
>
> I found full stepping, but with 2 coils energized ( half step position,
but
> full step increments ) gave me the best torque.
>
> John
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Pramod Kotwal
> Sent: 28 December 2000 10:55
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]:writing data to IBM PC parallel port to drive stepper
>
>
> This is about using an IBM PC parallel port to drive a bipolar stepper
> motor. So I hope it not too far off topic here.
>
> I would like to use C to to send the appropriate signal to the data port
> bits on the parallel port. P.H. Anderson gives a very nice and clear
> explanation of how to do it .
>
> The problem I have is in defining the delay between two subsequent
commands
> to write the bit to the port. This time interval will define how fast the
> motor will turn.
>
> The command to wrie data to the port is
> outportb(port address, data).
>
> The interval between writing data is controlled by the
> delay(time) command.
> This command seems to read time in milliseconds.
>
> If this correct, the shortest delay I can specify is 1 millisecond between
> steps. This would mean that on stepper motor with 200 steps per revolution
I
> can, at best get 5 rpm.
>
> This does not make sense to me. Where am I going wrong ?
>
> I will appreciate help.
> Pramod Kotwal
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads
>

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads