Re: PIC code etc.

At 08:04 28/02/2001 +0000, you wrote:

>What are you using to write code for the 16F877?

I use a commercial "C" compiler - see:

http://www.fored.co.uk/

The development system I am using is a beast called "Icebreaker" (see
http://www.magenta2000.co.uk/) - does in-circuit breakpointing etc. The
drawback is that it uses proprietary code in the PIC & only gives access to
the lower 4K of memory. Would be no problem to use a different dev board
though - FED supply one of their own.

>I have a friend using
>two in a dive computer. What do you do for the floating point?

I don't use floating point. For stepper drive use, integer/fixed point
calculations are much more useful - even essential - you don't want the
inherent rounding errors associated with floating point calculations to
creep up on you as accumulated errors in your calculation of the
current/desired position. With integer/fixed point calculations you can
always keep to within +- 1/2 step of the desired position if you do the
calcs right. However, that side of the project is early days yet...I'm
fighting with the user interface right now - provided by a 2 by 16
character LCD display plus a 16-key keypad. As always with this kind of
project, the "guts" of the software is less than 10% of the total needed to
interface the machine to a human operator in a sensible way. My prototype
will drive a stepper a known number of steps, ramping up & down between min
& max speeds; the next trick is to get the number of steps & the speeds
into the machine by some means other than using debug!

The driver stage is L297/L298; seems pretty easy to interface the PIC to
these devices. I haven't bothered to opto-isolate between the PIC and the
L297, and haven't seen that cause any problems as yet.

So far, I'm only attempting to drive one stepper; however, I don't see any
reason why the 16F877 shouldn't be able to handle a couple of motors, maybe
more, but I've not measured its maximum stepping rate yet. Certainly no
shortage of I/O lines on the PIC, and I am not making the most efficient
use of them right now.

Regards,
Tony