68HC11 Based Robot Help

[theinfamousbob]

I've built a small tank-tread robot with a 68HC11E2 chip, and am having some problems reading sensors. My motor outputs work fine, but the 'bot will only read one sensor, on the LSB line. I know both sensors work, because I can switch and it reads the other sensor on the LSB. When the 68HC11 boots in single-chip mode (like it's set to do right now), Port C (which I'm trying to use) defaults to all inputs. I'm just not sure why I can't read anything other than the LSB. My code is reading the entire byte, not just a bit. I'm using sbasic to write the code, which right now is set to trigger the left motor for the left sensor and the right motor for the right sensor. Any ideas/experiences?

-Infamous

 

[bananasiong]

I used 68HC11E9 to do my project last time, but in assembly language. Port C can be either input or output, you have to configure that port. How do you write the code for getting input from port C? Is the input pin floating?

 

[theinfamousbob]

The other (unused) inputs might be floating, I'll try modifying the DDRC to only accept on two bits...

The sensors have pull downs on them, so I know that's not the problem. I don't think the pins are really floating either, because the LSB always works, and the code isn't using binary; it's using plain 'ol integers.

 

[bananasiong]

how do you check the input?
for example, load port c to accumulator a, then it is ANDed with $01 (which is 00000001 in binary, so checking the LSB), then BEQ (Branch back if EQual to zero), otherwise, continue the following code.

Is it like that you check the input?

 

[theinfamousbob]

I'm writing in SBASIC (Google it, first hit is the download). It uses peek and poke, just like any other basic variant. I'm peeking at $1003 and pulling a byte from the port. I know there's a 16-bit peek as well; I'll try that today and see if it helps.

(There's just not enough time to learn assembly before the competition... )

 

[theinfamousbob]

Update...

Got it fixed. Didn't realize the sensors I built were active off...found that out pretty quickly (not...). I built the sensor boards without looking at the fact that it had a pull-up and not a pull-down.

Thanks for the help though!

 

[theinfamousbob]

The robot's finished...I've been up about 23 1/2 hours straight. School, then robot building, then work 'til midnight, then building until now. It works though. It's designed to move through a "journey course," with a hill in the middle. The link's here:

www.nationalroboticschallenge.org

Here's the Journey course:

**broken link removed**

I have to be there inside of 5 hours...oh joy!