Automous R/C Car

Scott Portocarrero

Ok so here is the veeerrry beginning of my code. All I am trying to do here is steer the car out of the way of an object when the car gets close. I understand that the car doesn't move forward yet. My Issues:

1) The rawdata coming from the PING has a value of no more that 250 with a home made servo extension cable attached. When I plug the PING directly into the bread board it give me the correct readings up to 5000. The question is why would an extension cable give me such a variance?

2) I am very new to PBasic. Can somebody look over my code and tell me what I am doing wrong, maybe give me some pointers. All I want it to steer right when something is detected close to the left PING and to steer left when something is detected close to the right PING. To me this sounds very simple but it doesn't work.

Heeeeellllllllllppppp!

Post Edited (Scott Portocarrero) : 7/13/2009 4:39:46 AM GMT

Scott Portocarrero

Anyone

dev/null

Change this part of your code:

IF rawdata1 < 200 AND rawdata2 < 200 THEN GOSUB Steer_Center
IF rawdata1 > 200 AND rawdata2 > 200 THEN GOSUB Steer_Center
IF rawdata1 > rawdata2 THEN GOSUB Steer_Left
IF rawdata1 < rawdata2 THEN GOSUB Steer_Right
IF rawdata1 = rawdata2 THEN GOSUB Steer_Center
PAUSE 20

GOTO Main

About the PING sensor, do you have a Voltmeter? Then you can check the cable for resistance, maybe its broken. This shouldn't happen to a PING and if the cable is ok, the PING might be damaged.

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Don't worry. Be happy

Scott Portocarrero

It didn't work. I think I need to get the values coming from the PING)) correct (in the 5000's) for this to work properly. What do you think?

dev/null

Try this:

IF rawdata1 > rawdata2 THEN 
   GOSUB Steer_Left
ELSEIF  rawdata1 < rawdata2 THEN
   GOSUB Steer_Right
ELSE
   GOSUB Steer_Center
ENDIF

PAUSE 20

GOTO Main

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Don't worry. Be happy

dev/null

You should add some slack to your measurements, so this will probably work better:
This way, there is a slack of 50 before you start turning.

IF rawdata1 > (rawdata2+50) THEN 
   GOSUB Steer_Left
ELSEIF  rawdata1 < (rawdata2 + 50) THEN
   GOSUB Steer_Right
ELSE
   GOSUB Steer_Center
ENDIF

PAUSE 20

GOTO Main

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Don't worry. Be happy

SRLM

You'd probably get more responses if you attached the file with the correct extension.

Scott Portocarrero

Oops!!!

Here it is

SRLM

Try making the raw data variables word sized. According to the documentation it can be up to 18 ms long. Also, you can make your steering routines much more efficient if you have just one routine that takes an argument of the direction. Something like this:

IF want go left THEN dir = SERVO_LEFT
ELSEIF want go straight THEN dir = SERVO_STRAIGHT
ELSEIF want go right THEN dir = SERVO_RIGHT
ELSE GOTO error

GOSUB steer

...

steer:

...
PULSOUT servo_pin, dir
...

Scott Portocarrero

Excuse my ignorance but is "want go left" a variable like:

want go left VAR BYTE
want go right VAR BYTE
want go straight VAR BYTE

What is GOTO error?

I feel like this is something very simple!

SRLM

Scott Portocarrero said...
Excuse my ignorance but is "want go left" a variable like:

It's my lazy pseudo code...

"want go left" would be the condition that determines a left hand turn. From your code, you used the comparison "rawdata1 > rawdata2".

I put the GOTO error in there as a catch all for debugging: if the robot shouldn't go left, right, or straight, what's else is there to do? You could determine that you have an error at that point.

As a side note, you used "IF rawdata1 = rawdata2 THEN Steer_Center". This case will almost never be true since there are ~65,000 possible values for rawdata1 and ~65,000 values for rawdata2. The chances that they are equal are very small. Instead, what you might want to do is to use ranges. For example, if the right sensor distance is less than 12 cm and the left sensor is greater than 12 then turn left.

edit: dev/null posted something similar, using the term slack.