[vcf-midatlantic] Why isn't my program working?

[Douglas Crawford]

On 2/1/2017 7:50 PM, Dan Roganti via vcf-midatlantic wrote:
> another update,
> this is regarding the original code found in the Teacher's manual
> which is how we started and arrived at this problem
> that was the pdf file in the "Lego Lines" Zip file, which also contained
> the disk image.
>
> We mentioned that Basic code was likely just demo code to fiddle some bits
> on the port address to spin a motor, blink a lamp, or sense a contact
> switch. As the Lego folks instead pushed their Lego Logo software, with
> it's flashy graphics to impress the kids in their education market. So,
> they apparently didn't use this Basic code in a live example, eg. integrate
> all of this code with their subroutines and the Main code into a
> functioning robot..
>
> The variable DB, which is used in each of their subroutines for the Read
> Port and Write Port operations, was getting corrupted in our version of the
> code. And this created that stuttering symptom. When any of these
> subroutines are used in separate programs, they work perfectly fine.
Oh Dang. Evan talked about the read of the port but we didn't see the code.
Shame on us for not asking to see the read port usage.
Seeing DB reused probably would have raised a red flag.

>
> And as we observed, our code also works perfectly fine when spinning just
> one motor. The only time the robot goes bezerk is when trying to spin
> multiple motors. Which is needed since the robot requires both motors for
> locomotion.
>
> So, I had to use separate variable for the Read Port and Write Port
> operations for that port address to the robot interface. So I just used DR
> for the Read Port, and DW for the Write port. And then the associated code
> in each Read and Write subroutine which used that variable was made to
> match as well.
>
> And so I sent Evan the latest disk image and everything works fine now with
> his robot. No more stuttering motors
> this is the screenshot from the program, its only 40col, a kind of
> telemetry display
> http://www.rogtronics.net/files/hobby/comp/apple/Robot-Lego/images/ROBOT0.671.jpg
> I was going to update the 80col version with this bug fix too, this is more
> of a flow chart display
> http://www.rogtronics.net/files/hobby/comp/apple/Robot-Lego/images/ROBOT0.68.jpg
>
> but since Evan's recent foray in learning Binary [hehe]
> he will continue using the new code we made with the hard-coded values
> recently
> Another attempt to use the Applesoft Basic compiler is another goal, to
> speed up eveything
> just have to find the disk images
>
> #$#%@^#$
> Dan