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Type: Posts; User: Jack Crenshaw

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by Jack Crenshaw
Replies
18
Views
1,129

Any of you ultra-experimenter types looking at this program?

Any interest? My guess is that you guys would love the challenge.

Jack
2. ## Thread: Real Random runs away from average zero

by Jack Crenshaw
Replies
45
Views
2,396

### I'm no expert on random numbers (those who are...

I'm no expert on random numbers (those who are experts tend to be very strange people! <g>), but I have studied the issue a lot. It's a fascinating topic because people spend many hours trying to...
3. ## Thread: PASM Devision routine that works for full 32 bit devision,Help Fix this one or

by Jack Crenshaw
Replies
25
Views
1,335

### It doesn't work that way, Phil. Or at least, it...

It doesn't work that way, Phil. Or at least, it shouldn't. rx should always be left justified, so that its high bit is always
a one. With that arrangement, rx ends up as \$1000_0000. Even if rx...
4. ## Thread: PASM Devision routine that works for full 32 bit devision,Help Fix this one or

by Jack Crenshaw
Replies
25
Views
1,335

### Actually, Phil, ra doesn't have to be smaller...

Actually, Phil, ra doesn't have to be smaller than rx. It only has to be smaller than twice rx,
so when you compute ra - rx, the high bit is always zero.
5. ## Thread: PASM Devision routine that works for full 32 bit devision,Help Fix this one or

by Jack Crenshaw
Replies
25
Views
1,335

### First off, it looks like you're not shifting far...

First off, it looks like you're not shifting far enough. You're shifting only 16 bits, where 153_333_333 is a 27-bit number.

As one of your tests, you should always be able to divide by 1, and...
6. ## Thread: A simpler approach to a Prop-based compiler?

by Jack Crenshaw
Replies
17
Views
1,020

### I'm confused -- which seems to be my default...

I'm confused -- which seems to be my default state in this forum.

Seems to me the discussion revolves around four decisions, three or which are binary:

1) develop on host or target Prop?
2)...

by Jack Crenshaw
Replies
30
Views
2,926

### Well, that's a good point. I suppose that, in...

Well, that's a good point. I suppose that, in the case of the human, we've turned the whole body into an accelerometer. Point taken.

But that's precisely the point.

This discussion...

by Jack Crenshaw
Replies
30
Views
2,926

### You miss my point. The discussion was not about...

You miss my point. The discussion was not about feet and toes, but about sensing where down is. I was trying to explain, by analogy, that you (or your robot) don't need gyros or accelerometers to...

by Jack Crenshaw
Replies
6
Views
1,028

### CO Sensor

I see that Parallax now has a neat CO sensor. It's interesting to me because, years ago, a friend and I were trying to build a CO detector for RVs and mobile homes. We found a raw sensor that put...

by Jack Crenshaw
Replies
30
Views
2,926

Let's think about this for a moment. Suppose I'm standing. To make it more challenging, assume that I'm blindfolded and the nerves from my inner ear have been surgically cut.

Will I be able to...
11. ## Thread: Nav using GPS and the Prop: What to Expect?

by Jack Crenshaw
Replies
37
Views
5,719

### Yep, you're absolutely right, Dennis. About a...

Yep, you're absolutely right, Dennis. About a second I posted my message, I realized that the GPS, though it does indeed know where North is, it doesn't know
your attitude <mine is awful some days...
12. ## Thread: Nav using GPS and the Prop: What to Expect?

by Jack Crenshaw
Replies
37
Views
5,719

### Ken, I don't think you need the compass. The GPS...

Ken, I don't think you need the compass. The GPS system knows where North is.

Jack

by Jack Crenshaw
Replies
27
Views
4,221

### I think I said, early on, that any nav sensor...

I think I said, early on, that any nav sensor device works better (or only if) it's trimmed by another. The gyro/GPS combo is a natural. Way back when, I used to work on nav systems. We worked hard...

by Jack Crenshaw
Replies
27
Views
4,221

### My stepson flies an ultralight for a living...

My stepson flies an ultralight for a living (rough duty!), often hundreds of miles. He tells me that if you have a GPS, you pretty much don't need any other instrument. The GPS gives you, after all,...
15. ## Thread: Approximating Trig Functions

by Jack Crenshaw
Replies
14
Views
1,129

### Re the arctan algorithm: I've looked at all the...

Re the arctan algorithm: I've looked at all the messages in the thread, and the threads referenced by SRLM
http://forums.parallax.com/forums/default.aspx?f=25&m=310282
and Rayman...
16. ## Thread: Approximating Trig Functions

by Jack Crenshaw
Replies
14
Views
1,129

### The problem with CORDIC is its speed. But I agree...

The problem with CORDIC is its speed. But I agree with you: If there's no hardware multiply, CORDIC is as fast as the multiply itself.

Jack
17. ## Thread: Approximating Trig Functions

by Jack Crenshaw
Replies
14
Views
1,129

### And exp(x)? And atan(x)? If yes, all problems...

And exp(x)? And atan(x)? If yes, all problems are solvable!

Jack
18. ## Thread: Approximating Trig Functions

by Jack Crenshaw
Replies
14
Views
1,129

### Andrew, before parking the atan function, take a...

Andrew, before parking the atan function, take a look at the continued-fraction form. It converges MUCH faster than the power series. It's also way cool:

When you truncate the fraction at some...
19. ## Thread: Approximating Trig Functions

by Jack Crenshaw
Replies
14
Views
1,129

### Well, dang! There I go again, trying to solve...

Well, dang! There I go again, trying to solve problems that don't exist. Is there anything Chip didn't think of already?

Guess I'd better read the manual before I post any more speculations.
...
20. ## Thread: Approximating Trig Functions

by Jack Crenshaw
Replies
14
Views
1,129

### I forgot to mention: Someone's bound to point...

I forgot to mention: Someone's bound to point out the CORDIC solution. That's really a subset of the notion of splitting up the angle range into segments. Splitting the full angle range, 0..360,...
21. ## Thread: Approximating Trig Functions

by Jack Crenshaw
Replies
14
Views
1,129

### Approximating Trig Functions

Pi Guy's recent posts concerning the math of ping radar bring up an interesting and perennial problem: Given a range and an angle, how do you computer the equivalent vector in Cartesian coordinates?...
22. ## Thread: math on the prop

by Jack Crenshaw
Replies
27
Views
2,215

### PG, I said "Cartesian vector," not "cartesian...

PG, I said "Cartesian vector," not "cartesian filter."

>Can it find me x and y coordinates?

The x- and y-coordinates _ARE_ the Cartesian vector. You seem to be trying to compute these...
23. ## Thread: math on the prop

by Jack Crenshaw
Replies
27
Views
2,215

### Dang! Forget all my ideas about swiveling a...

Dang! Forget all my ideas about swiveling a sensor. I see that you guys were about 3 years ahead of me.

Story of my life.

Sounds like what Pi Guy needs is a sin/cos decoder. Not sure how...
24. ## Thread: math on the prop

by Jack Crenshaw
Replies
27
Views
2,215

### Guys, I've got so many things to say, I don't...

Guys, I've got so many things to say, I don't know which one to say first. How about:

@tracy: I just read the thread from 2006. Sorry, guys, but there's no shortcut to using Cartesian...
25. ## Thread: COGNAC - Cog Native Asm Compiler

by Jack Crenshaw
Replies
91
Views
5,310

### heater: I _LOVE_ it!!!! Jack

heater: I _LOVE_ it!!!!

Jack
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