In lugnet.robotics, Kevin L. Clague wrote:
> In lugnet.robotics, Steve Hassenplug wrote:
> > In lugnet.robotics, Kevin L. Clague wrote:
> > > I've got some questions about the LEGWAY software.
> >
> > > Part of the index you use into motor speed array is sys_time & 7. I do not
> > > understand this at all. I can only imagine that over time you try to force
> > > migration from one motor drive state to the next.
> >
> > This is the part that does all the work controlling the motors.
> > Between this array:
> > ---
> > int MotorSpeedArray[32] = {1,1,1,1,1,1,1,1,
> > 3,3,3,3,3,3,3,3,
> > 2,2,2,2,2,2,2,2,
> > 0,0,0,0,0,0,0,0};
> >
> > // motor speed 0-7 = forward, 0 = fast, 7 = slow
> > // motor speed 8 = stop
> > // motor speed 9-16 = reverse, 9 = slow, 16 = full
> > // 24 = float
> > ---
> > and these lines
> > ---
> > MotorRunningValue = (sys_time & 7);
> > motor_a_dir(MotorSpeedArray[MotorRunningValue + MotorA]);
> > motor_c_dir(MotorSpeedArray[MotorRunningValue + MotorC]);
> > ---
>
> I understand the value of everything *except* MotorRunningValue which is a value
> in the range of 0 to 7, which increments every millisecond. But I don't
> understand how it helps.
> >
> > Clear yet?
>
> Nope. It would seem that over time, you move further down the array, until
> MotorRunningValue goes to 0, and you start over....
>
> This has the potential of moving you from forward, through stop, and then
> reverse. How does this help?
Let me try with a couple examples.
Given the above code, if you set MotorA=0, the motor direction will be set to 1
for the first ms (MotorRunningValue==0; 0+0=element 0 in array) and
1 for the second ms (MotorRunningValue==1; 0+1) and
1 for the eighth ms (MotorRunningValue==7; 0+7 element in array), then
MotorRunningValue will be set to 0, and it will start over.
So, the table would look like this:
MotorSetting = speed for 1ms slice of time
0 = 1,1,1,1,1,1,1,1 // full forward for 8ms, repeat
1 = 1,1,1,1,1,1,1,3 // forward for 7 ms, stop for 1ms, repeat
2 = 1,1,1,1,1,1,3,3 // stop for 2ms
3 = 1,1,1,1,1,3,3,3
4 = 1,1,1,1,3,3,3,3 // running for 50%, stopped for 50% or 1/2 speed
5 = 1,1,1,3,3,3,3,3
6 = 1,1,3,3,3,3,3,3
7 = 1,3,3,3,3,3,3,3 // running very slow. Full speed for 1ms, stop for 7ms
8 = 3,3,3,3,3,3,3,3 // stopped
9 = 3,3,3,3,3,3,3,2 // slow reverse
10= 3,3,3,3,3,3,2,2
11= 3,3,3,3,3,2,2,2
12= 3,3,3,3,2,2,2,2 // 1/2 speed reverse
13= 3,3,3,2,2,2,2,2
14= 3,3,2,2,2,2,2,2
15= 3,2,2,2,2,2,2,2
16= 2,2,2,2,2,2,2,2 // reverse all the time
And if you just want to float the motors:
24= 0,0,0,0,0,0,0,0
It will never go forward, through stop, then reverse with a single motor
setting. Because MotorRunningValue goes from 0 to 7 (eight steps) and there are
eight steps in each section of the array. Lucky? well, maybe. :)
understand, yet?
Steve
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