A few simple programming questions;
 

Well, First we have a few problems so I'll label them. I'll upload the code at the end, so far its all in the user_routines.c

1. I'm not sure anymore if I am programming the buttons correctly, I don't know much about C so its a good problem I'm messing up somewhere. Here is one part I am trying the buttons will do the "else" part but will not do the if part of it. I'm sure I am doing something wrong here so help is nice.
if(p3_sw_top == 1)
{
pwm09 = 127;
pwm10 = 127;
}
else
{
pwm09 = 254;
pwm10 = 254;
}
and
if(p3_sw_trig == 1)
{
pwm09 = 0;
pwm10 = 0;
}
else (p3_sw_trig == 0);
{
pwm09 = 254;
pwm10 = 254;
}

2. We are using spikes this year, and I am not sure how to program them, I'm sure I have to program it somehow but I am at a lost of how to.

3. I am getting a syntax error at line 467 in our user_routines.c...The code ends at 466, before that really cause the last few lines are the from the /**/ stuff. I hope I put the code on here correctly. If not I'll edit it after I post.

4. I'm still looking but can someone tell me where to get a white paper about limit switches, this isn't something I am worrying to much about now, though. I'll just have to play with it later. Which will me create a few threads in the future most likely.

Thats all, I know its a lot, but I'm the only programmer on the team and I know nothing about C. So I would really appreciate any help you guys can give me. Also sorry the code is kinda sloppy, I have been commenting things in and out adding so much stuff it makes my brain hurts. I'll also give a cookie to all who help :D
Thanks
Josh

Re: A few simple programming questions;
 

Sorry I'm not being as big of a help as I should be, but I'm in the middle of homework and just answering the questions where the solution is on the top of my head.

You don't need (p3_sw_trig == 0) after the else, it's already implied. Also, (this may be wrong because I haven't written code like this in 2 years) I think you only need one = when referring to the value of the button, not ==.

The PWM cable from the Spike goes into one of the Relay outputs on the robot controller. Then you just map which buttons you want to control which relays and you're good. Not sure if you know how to or not, but send me a PM if you want to know how to have one button control the in/out of a piston and such (like if you want a solenoid to act like a festo).

Re: A few simple programming questions;
 

The portion highlighted in red is a syntax error. There are two ways to correct the error. Since the value of the variable can only be 0 or 1 you can just delete the portion in red. Or you can change the syntax to:

Re: A few simple programming questions;
 

Changing to a single = would be legal but have a totally different meaning and in this case be wrong. A single = would cause an assignment to occur instead of doing a comparison.

Re: A few simple programming questions;
 

This might be your intention, but with this code, the pwm's will only be at 127 when the button is held down, when the button is not held down, they will be at 254.


With spikes, you would basically program them using two variables. If your spike was hooked up to relay1, then your two variables would be:
relay1_fwd and relay1_rev. If you wanted to fire the spike in one direction, you would set:

The other direction would be:

And neutral would be:
If you were to have the condition after the else, despite the fact that it's not needed, since the button can only be at 1 or 0, and if it isn't at 1, then a value of 0 is implied, the statement would have to be an

You also should not have a semi-colon right after an if or else statement.

This is not true. The '==' operator is the equality operator in C, '=' is the assignment operator, which would set the variable equal to what you are comparing it with, and the condition would always be true.

Regarding the syntax error, from a brief glance at the code, it looks like you might be missing a brace or two. Try adding them one by one to the end of your code, and see if that helps.

Hope this helps,

Re: A few simple programming questions;
 

in the printf statement put in the end ...%d\r",

You can also change the stuff in the quotes to print what every you want.

Re: A few simple programming questions;
 

is that a line of code or only a comment in your post?

Im almost certain there is no IF AND ELSE statement ?

Re: A few simple programming questions;
 

You are correct. A search shows that syntax was not used in his code.

Re: A few simple programming questions;
 

I see you have an unmatched bracket here that will give you the syntax error. My main suggestion would be to change how you are commenting out lines and blocks of code.
Switch over to the // form rather than use the /* */ form.
Your blocks are ending in random places.

Re: A few simple programming questions;
 

Technically, it's not implied. The code within the segment following the else executes no matter what if the first IF and all IF ELSEs after it fail.

Another correction: == is an operator that returns a one or a zero based on whether the LHS (left hand side) is equal to the RHS. the = operator sets the LHS (which has to be a valid LHS, aka a variable) equal to the RHS. It returns the set value. C will let you get away with this:

if (x = 5)
stuff();

It assumes, "Oh, I know what he wants to do. He wants me to set x to five and then check to see if x or not." AKA, this will not cause a compile time error, whereas in Java it will.

Note that the == returns a 1 or a 0, not any boolean value, for those used to Java or other such. The other comparisons (>, < , <=, >=, etc) work the same way.

Neat but terrible shorthand (don't do this):

x += x < 100;

Which does? I throw it out there.

Paul Dennis

Re: A few simple programming questions;
 

You're absolutely right, Mark. The problem is that the code is poorly written. IE, the original code that they gave us. Whoever writes the code apparently hasn't come to the realization that C++ style comments (//like this) are available in C now. It used to be that /*this*/ was all there was. However, it's bad coding practice to write one liners like this:
Because if you want to block comment that line and a bunch of other like it, you will not be able to easily because the */ at the end will also end yours! The easiest way I have found around this without bothering to change the code (i.e. change /**/ to //) is to use this:

Alright, that's all for now folks. I think cruella wants to make a coat out of my posts.

Paul Dennis

Re: A few simple programming questions;
 

Ooh, clever. Dangerous, but clever. It increments x unless it's already 100 or greater.
It's true, C does give you enough rope to shoot yourself in the foot.

Re: A few simple programming questions;
 

I agree, it should be no IF, AND, or BUT statements. :)

Re: A few simple programming questions;
 

Yes it does. I came up with this one myself... a very interesting mix of metaphors there. I would use the ++ but it's all semantic.

But there is absolutely no reason to do this. It doesn't save you any time, and it doesn't save you an space in memory. However, there is, and I kid you not, a contest to obfuscate code. This is a fairly simple example of that.

Paul Dennis

Re: A few simple programming questions;
 

I've seen bugs introduced when people use pre or post ++ at the wrong time.

I agree with you on making code readable. Years ago I encountered a line of code written by a guy -- it was doing some sort of math but had around 10 different operators in one line including bit and math operators and was impossible to understand. And this was in production software that a team of people had to maintain.

Even something as simple as always using parentheses to establish precendence instead of relying on operator precendence makes code much more understandable.