Need help in basic coding!

V360

So, i have been reading through examples of line follower codes. There's something i don't get.

' QtiLineFollow.bs2
' Boe-Bot follows electrical tape with 3 QTI modules.
'{$STAMP BS2}
'{$PBASIC 2.5}
qti VAR Nib
DO
Right: HIGH 5: PAUSE 1: qti.BIT0 = IN3: INPUT 5
Center: HIGH 6: PAUSE 1: qti.BIT1 = IN3: INPUT 6
Left: HIGH 7: PAUSE 1: qti.BIT2 = IN3: INPUT 7
SELECT qti
CASE %010 ' Forward
PULSOUT 13, 850
PULSOUT 12, 650
CASE %011 ' Pivot right
PULSOUT 13, 850
PULSOUT 12, 750
CASE %001 ' Rotate right
PULSOUT 13, 850
PULSOUT 12, 850
CASE %110 ' Pivot Left
PULSOUT 13, 750
PULSOUT 12, 650
CASE %100 ' Rotate Left
PULSOUT 13, 650
PULSOUT 12, 650
ENDSELECT
PAUSE 20
LOOP

WHat does the bolded part means?
1. Why do i have to set the·3 input pins to high initially?
2. qti.BIT0 = IN3 :· Why do all of the 3 bits of variable qti = IN3?·
3. What does the INPUT 5,6,7 behind indicates?



thanks in advance

Mike Green

Pins 5,6, and 7 are the IR emitters of each of the sensors. They get turned on (supplied power) when needed with the HIGH statement and turned off when not needed using the INPUT statement. Since the QTI sensors have an "open collector" output setup, all of them can be connected together and attached to pin 3. Only the one with an active IR emitter should respond by making its output low (or zero). See the QTI documentation for details.

V360

Thanks Mike, now i have another problem, how should i change the coding if i were to include ramping in it?
Examples would be much appreciated.

Mike Green

I would first ask what you mean by ramping. Remember that there's no direct relationship between servo speed and the control pulse width other than the further the pulse width is from center, the faster the motor goes. It can be somewhat non-linear and will vary from servo to servo.

The easiest way to do ramping is to use a FOR loop and to do something like:

for i = 0 to 100 step 10
  pulsout <pin>, 750+i
  pause 20
next i
do
  pulsout <pin>,850
  pause 20
loop

In your case, you've got a more complicated situation. How would you do the same
thing in your case? Remember, each time through your loop, you want to have the
servos go a little faster until they reach the desired speed.

V360

Hmm Mike,
As my boebot jerks when it turns, so i have to use ramping to smoothen the turn. Well that's what i mean.
I pretty much understand your example, but i have no idea how to apply it in my program so that my boebot would turn smoothly.
Sorry to trouble you again, but can you give a detailed example of ramping when the boebot is turning?
Lets say when only the right and middle LEDs detect the black line,

CASE %011 ' Pivot right
PULSOUT 13, 850
PULSOUT 12, 750
How do i modify the code above to smoothen the turning?

Thanks in advance.

Mike Green

I don't think you can just modify a little piece of your program. You're going to have to change the way the whole program works.

Add two variables, oldQti as a nibble and goal as a byte. Initialize oldQti to 15 and goal to 0.

Before the SELECT, do something like:

IF qti <> oldQti THEN
   goal = 0 : oldQti = qti
ENDIF

Before the PAUSE, do something like:

IF goal < 100 THEN
   goal = goal + 10
ENDIF

Then, anywhere in your SELECT statement where you have 850, put 750+goal. Anywhere you have 650, put 750-goal.

What this does is to set a goal anytime the QTI value changes. If QTI doesn't change, the program moves closer to its goal every 20ms. Once the program reaches its goal, it stays there until QTI changes again. The goal is used to set the speed of the servos. It takes about 200ms for the goal to be reached.

V360

Thanks Mike,
·From my understanding, the modification you taught me allows the boebot to move from 750 to max speed, which means increase in speed.
Do i have to include so that the boebot reduce its speed whenever it changes direction?
I mean, moving from 750 to maximum speed is enough to prevent jerking?


Post Edited (V360) : 4/15/2008 4:31:13 PM GMT

Mike Green

I don't know. Try it and see. You may find that you need to move smoothly from one direction to another and that you do need to deccelerate as well so the program may get even more complicated. Ramping the speed up and down takes time and that may slow the response in the line following so that doesn't work as well. Keep in mind that the speed of the servos is not a linear function of the pulse width. It can vary from servo to servo. The step size (10) and maximum adjustment (100) may need to be different for each servo. Only experimentation will tell you.

V360

Hey Mike,

I tried the modification for ramping, and the boebot aint working at all. Can you please look through my code

'{$STAMP BS2}
'{$PBASIC 2.5}

'left->5
'right->7
'0 -> detect
'1 -> no detect
left VAR Bit
right VAR Bit
old VAR bit
goal VAR byte
new VAR byte
speed VAR bit
old=15
new=1
speed=0
DO
IF new <> old THEN
speed= 0 : old = new
ENDIF
'············ Forward
IF (IN5=1) AND (IN6=0) AND (IN7=1) THEN
GOSUB Forward
'==========================================================
'············ Right Turn
ELSEIF (IN5=1) AND (IN6=0) AND (IN7=0) THEN
GOSUB Pivot_right
GOSUB Store
ELSEIF (IN5=1) AND (IN6=1) AND (IN7=0) THEN
GOSUB Rotate_right
GOSUB clear
'==========================================================
'············ Left Turn
ELSEIF (IN5=0) AND (IN6=0) AND (IN7=1) THEN
GOSUB Pivot_left
GOSUB Store
ELSEIF (IN5=0) AND (IN6=1) AND (IN7=1) THEN
GOSUB Rotate_left
GOSUB clear
'==========================================================
ELSEIF (IN5=1) AND (IN6=1) AND (IN7=1) THEN
······· IF(left=0)AND (right=1)THEN
······· GOSUB Rotate_left
······· ELSEIF(left=1)AND(right=0)THEN
······· GOSUB Rotate_right
······· ENDIF
'==========================================================
ENDIF
IF goal < 100 THEN
·· goal = goal + 10
ENDIF
'PAUSE 20
LOOP

Forward:
PULSOUT 13, 750+speed
PULSOUT 12, 750-speed
new=1
RETURN

Pivot_right:
PULSOUT 13, 750+speed
PULSOUT 12, 750
new=2
RETURN

Rotate_right:
PULSOUT 13, 750+speed
PULSOUT 12, 750+speed
new=3
RETURN

Pivot_left:
PULSOUT 13, 750
PULSOUT 12, 750-speed
new=4
RETURN

Rotate_left:
PULSOUT 13, 750-speed
PULSOUT 12, 750-speed
new=5
RETURN

Store:
left=IN5
right=IN7
RETURN

clear:
left=1
right=1
RETURN

Mike Green

I don't know why you've added "speed", particularly when it's defined as a bit. It should be "goal". This suggests to me that you're adding pieces before you understand previous pieces ... not a good idea. Always add new functionality a little piece at time, make sure it works and make sure you understand what it's doing before you add the next piece.

V360

Hm.. okay, i will try it again, and will keep you updated. Thanks

V360

Well mike,
I have tried it over and over again in the past few days, and i am making no progress at all.
First of all, the boebot cant follow the line if there's a sharp turn less than 90 degrees.

Secondly, my boebot is still jerking. Can you teach me to slow the boebot down before each turn?

Thank you.

Franklin

Can you ATTACH your code as it exists now?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- Stephen

V360

'{$STAMP BS2}
'{$PBASIC 2.5}


'left->5
'right->7
'0 -> detect
'1 -> no detect

store5 VAR Bit
store7 VAR Bit
'==========================================================
DO
' Forward
IF (IN5=1) AND (IN6=0) AND (IN7=1) THEN
GOSUB Forward
'==========================================================
' Right Turn
ELSEIF (IN5=1) AND (IN6=0) AND (IN7=0) THEN
GOSUB Pivot_right
GOSUB Store
ELSEIF (IN5=1) AND (IN6=1) AND (IN7=0) THEN
GOSUB Rotate_right
'==========================================================
' Left Turn
ELSEIF (IN5=0) AND (IN6=0) AND (IN7=1) THEN
GOSUB Pivot_left
GOSUB Store
ELSEIF (IN5=0) AND (IN6=1) AND (IN7=1) THEN
GOSUB Rotate_left
'==========================================================

ELSE
IF (store5=1) AND (store7=1)
'stop
ELSEIF(store7=0)AND (store5=1)THEN
GOSUB Rotate_right
ELSEIF(store7=1)AND(store5=0)THEN
GOSUB Rotate_left
ENDIF
ENDIF
'PAUSE 20
LOOP


Forward:
PULSOUT 13, 800
PULSOUT 12, 700
RETURN

Pivot_right:
PULSOUT 13, 800
PULSOUT 12, 750
RETURN

Rotate_right:
PULSOUT 13, 800
PULSOUT 12, 800
RETURN

Pivot_left:
PULSOUT 13, 750
PULSOUT 12, 600
RETURN

Rotate_left:
PULSOUT 13, 700
PULSOUT 12, 700
RETURN

Store:
store7=IN7
store5=IN5
RETURN


By the way the boebot is still jerking pretty badly. But the priority is to solve the sharp turns first.
Anyway thanks.