Posted by Joe Johnson. [PICTURE: SAME | NEW | HELP]
Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.
Posted on 10/21/99 9:07 PM MST
In Reply to: Hi, I’m new to the competition and need some help posted by Michael on 10/20/99 9:36 PM MST:
As to Controls: I say know thy self. If you don’t have the skills, stick with the basics.
Most of the tricks really come down to easing the tasks that the drivers have to do.
For instance, you may write some code to make a single button make motor A turn on then Motor B a few seconds later, then stop after 5 seconds. This same task could be done by the drivers (with practice) but it is easier and more reliable to do it in software (sometimes!).
So…
I recommend that you just make simple changes to the standard code until you know enough to do more (perhaps in year two). AND give your drivers enough time to make due without such one step buttons.
A skilled driver makes up for almost ANY software enhancements you could have made.
As to wiring: Things are pretty simple. Switches all get wired in to one connector. Sensors also get wired to that connector. FIRST is pretty specific about how the wiring has to be done so there is not a lot of freedom to get into trouble. The motors will be very simple this year because if what I here is true is in fact true all motor current will go to ‘off board’ directly to either a relay module (Full Forward/Off/Full Reverse) or a speed control (Variable Forward/OFF/Variable Reverse).
For Rookie Teams with little electrical experience I would recommend making all your mechanisms capable of running to full travel without damage. I would also recommend that you try to put switches that stop the motion at the end of travel for the strongest mechanism in order to save wear and tear. It may take some simple program changes to make this work, but it is fairly easy to do. We can walk you through it on this board if you need more help.
Variable feedback, from potentiometers is a very powerful tool for positioning arms, etc. but unless you have good electrical folks and very good programmers, I would not recommend it for a rookie team
As to books on the subject, I like the Parallax manual pretty well. Tom Frank has recommended another book elsewhere on this forum. I will find the link to the message and post it below.
Back to programming, keep in mind that if the new controller is like the old controller, users will have no real direct access to the pins of the STAMP2. The only pin that you can directly reach the outside world with was one user LED on the board. This was not very useful for using all the count or pulse or other cool I/O things that a STAMP2 has ‘built in’
Basically, the only I/O we had access to was the PWM outputs that controlled the speed controller (we output 8 8bit numbers that controlled up to 8 motors 0-full reverse, 127 full stop, 254 full forward), the relay outputs (a single 16 bit number that turned up to 8 motors full on, full off or full reverse), the input port (a single 16 bit number that indicated the position of up to 16 switches), the analog port (4 8 bit numbers that indicated the state of up to 4 sensor inputs, e.g. a the rotary position of a potentiometer), and finally the radio input (which was a bunch of data indicating the state of various joysticks, pots and switches on the operator interface side of things). Oh yeah, there was also an LED that your control program could flash red or green.
This indirect I/O scheme basically made about 90% of the functions of the STAMP2 unneeded by us FIRST folks. This will make your job a little easier, since you will have fewer functions to learn.
Good Luck.
Joe J.
P.S. I could not find the message about the STAMP2 book that Tom Frank recommended. Anyone know where to find that book title (Tom?)