Calculation goes wrong (Float32)

PlaneTeeR · 2006-05-17 19:18

Hello everyone,

I've got this program on mij BOE with a LCD and a Hall-sensor.

It meassures the time between pulses and then it calculates the speed.

I use the Float32 klasse also so mayby this is a good question for you peter.

The First reading is good, but then it went wrong! Check the result:

(ms = time between pulses in ms)

output javelin

Km/h 3.7716„
ms 1909
Km/h 4.9422
ms 2747
Km/h 7.546
········· 4
ms 2358
Km/h 13.832165
ms 1964
Km/h 15.788139
ms 3154
Km/h 24.56236
ms 2314
Km/h 28.03g
ms 3154
Km/h 47.607
ms 2120
Km/h 69.89ü8
ms 2452
Km/h 167.19589
ms 1505
Km/h 304.1ý4
ms 1979

Also there are sometimes strange symbols.

I've attached my java code...

Johnny

Peter Verkaik · 2006-05-17 20:02

You must reset o to "2.0" for each speed calculation.
I corrected your code in the attachement.
Also, do not use + to concatenate strings.
The javelin has no garbarge collection, so the use of +
leads to OutOfMemory errors.

regards peter

Post Edited (Peter Verkaik) : 5/17/2006 8:05:41 PM GMT

PlaneTeeR · 2006-05-18 11:50

Dear Peter,

With your corrected code I get a error:

[noparse][[/noparse]Error IDE-0024] Unknown bytecode in the JEM file (dup2_x2)

Johnny

Peter Verkaik · 2006-05-18 12:20

I put a try/catch block in the code.
That sometimes·resolves the Unknown bytecode error.
regards peter

PlaneTeeR · 2006-05-18 12:51

Yes i saw it, i made the code to difficult at first and this works.

I want to display the speed in this format 00.0 Km/h.

How do i get this done?

Johnny

·

Peter Verkaik · 2006-05-18 13:01

You calculate the 10x speed and takes only the integer part.
Then print speed/10, the decimal point, speed%10
See the attachement
regards peter

PlaneTeeR · 2006-05-18 17:11

Dear Peter,

I only can send Strings to my LCD so it does work on PC println but the not on my LCD (BPI-216).

So is there another method?

Johnny

Peter Verkaik · 2006-05-18 17:52

The idea is to send speed/10 to your lcd, then "." and then speed%10.
I always use the Format class to assemble strings in memory
char[noparse]/noparse buf2 = new char[noparse][[/noparse]6]; //allow xxx.x plus closing 0
int k=0;
k = Format.bprintf(buf2,k,"%d.",speed/10);
k = Format.bprintf(buf2,k,"%d",speed%10);
buf2[noparse][[/noparse]k]=0; //now buf2 holds nullterminated string
myLCD.write(buf2.toString()); //print string to LCD

I am not sure about toString for a nullterminated char array.
Basically, all buf2[noparse][[/noparse]i] that are not zero, starting at i=0, must be
appended to a StringBuffer, which may be converted to String.

regards peter

PlaneTeeR · 2006-05-18 19:35

Peter, i have an error that says: No method named toString() was found in type Char[noparse]/noparse

Johnny

Peter Verkaik · 2006-05-18 19:39

That's what I feared.
add this to the code:
StringBuffer buf3 = new StringBuffer();
int j=0;
while (buf2[noparse][[/noparse]j]!=0) {
· buf3.append(buf2[noparse][[/noparse]j]);
· j++;
}
myLCD.write(buf3.toString());

regards peter

·

PlaneTeeR · 2006-05-18 19:54

This works, thanks another problem solved!

Johnny

PlaneTeeR · 2006-05-18 21:22

One last question, can i do it completely without the Float32? And for the print to the LCD use the format class?

Peter Verkaik · 2006-05-18 22:04

The resulting formula for 10x speed [noparse][[/noparse]km/h] = 72,000 / time[noparse][[/noparse]ms]
You can use the UnsignedIntMath class to calculate 2/time
Then use umulf() to calculate integer * fraction (eg. speed = 36000 * (2/time))

int speed =·UnsignedIntMath.umulf((short)36000,UnsignedIntMath.ufrac(2,time));

then you don't need Float32.
The UnsignedIntMath class is much smaller than Float32
and is located here:
http://groups.yahoo.com/group/JavelinCode/files/Javelin%20Stamp%20IDE/lib/stamp/math/

The results should be about the same (I expect differences +-0.1 or so compared to Float32)

regards peter

Post Edited (Peter Verkaik) : 5/19/2006 9:36:11 AM GMT

PlaneTeeR · 2006-05-19 09:26

oke i have an Integer value, but i need a string to send to my LCD

Peter Verkaik · 2006-05-19 09:35

You do that the same way how you did it
with the integer value obtained from Float32,
that is with the Format class and a StringBuffer.

regards peter

PlaneTeeR · 2006-05-19 22:53

Also i have to display the distance, can i do this the same way.
(I use an this way to count the distance after every pulse dst=dst+2[noparse];)[/noparse]
The distance must be showed as 0000.00 KM but as you can see 2 is in meters so its of the scale.

Johnny

Peter Verkaik · 2006-05-19 23:21

If you want to keep distance up to 9999.99 then I
suggest to use 2 integers:
int dstKm that holds the integral Km
int dstm that holds the fractional Km in meters
For updating your distance
· dstm = dstm + 2;
· if (dstm == 1000) {
··· dstKm++;
··· dstm = 0;
····if (dstKm == 10000) dstKm = 0; //wrap from 9999 to 0000
· }

For printing distance:
· k = Format.bprintf(buf2,0,"%04d",dstKm);· //print 0000 to 9999
· k = Format.bprintf(buf2,k,".%02d",dstm/10);· //print .00 to .99
· buf2[noparse][[/noparse]k]=0;

Then convert to String as in previous code.

regards peter

PlaneTeeR · 2006-05-21 13:39

Peter,

The code works good, but after a while it gives an error see picture.

Tis is weird, why out of memory? I don't storage information or something!

Also added the code.

Johnny

Peter Verkaik · 2006-05-21 13:52

You used new char[noparse]/noparse and new StringBuffer inside while (true) loop.
I defined·buf0 to buf3 as static global buffers.
That should resolve the outofmemory problem.

regards peter

PlaneTeeR · 2006-05-21 13:55

Why does that give a out of memory?

PlaneTeeR · 2006-05-21 14:08

Hmm,

With this code it writes the values all over the LCD and misses very much readings!

I don't get this!

Johnny

Peter Verkaik · 2006-05-21 14:35

One problem with the setup is that you increment the distance by a fixed amount
everytime through the while (true) loop. If pulses are missed (and I think that is likely
because calculation and printing takes some time) the calculated distance is lower
than the actual distance.
In attached program I calculate the travelled distance for the time it takes to run
a single loop. The travelled distance is in 0.1 m units.

Let me know the results.
regards peter

Peter Verkaik · 2006-05-21 15:23

I checked the BPI216 class, and besides the write(String s) method that you use,
it also has a write(StringBuffer s) method, so the conversion from StringBuffer to String
is not required. Both StringBuffer and String variants call write(int CG) for each
character in the StringBuffer or String. So you can write directly from the buffers.

I did this in the attached file. This reduces the loopTime.

regards peter

Post Edited (Peter Verkaik) : 5/21/2006 3:35:01 PM GMT

PlaneTeeR · 2006-05-21 16:40

I don't think it's that, this code works but not alwayss accurate.

To calculate the distance you simply add the circumference each time there's a pulse.

I looked at what it printed and this is the result:

output
1
19.2
2
19.2 26.4
3
19.2 26.4 28.1
4
19.2 26.4 28.1 4.5
5
19.2 26.4 28.1 4.5 31.8
6
19.2 26.4 28.1 4.5 31.8 56.7
7
19.2 26.4 28.1 4.5 31.8 56.7 20.2
8
19.2 26.4 28.1 4.5 31.8 56.7 20.2 72.0
9
19.2 26.4 28.1 4.5 31.8 56.7 20.2 72.0 57.6

As you can see the results are printed after each other in the char.

This is started when we made them global.

I tried to make the buf null but that doesn't work here?

Johnny

Peter Verkaik · 2006-05-21 17:41

Try the attached program and tell me the
results that are printed to the jide message window.

regards peter

PlaneTeeR · 2006-05-22 10:00

Hey Peter,

The program works fine, but i'm curious.

When we made the chars and stringbuffers globally it went wrong.

As you can see the value's of the chars and stringbuffers were added after each other.

output km/h javelin

19.2
19.2 26.4
19.2 26.4 28.1
19.2 26.4 28.1 4.5
19.2 26.4 28.1 4.5 31.8
19.2 26.4 28.1 4.5 31.8 56.7
19.2 26.4 28.1 4.5 31.8 56.7 20.2
19.2 26.4 28.1 4.5 31.8 56.7 20.2 72.0
19.2 26.4 28.1 4.5 31.8 56.7 20.2 72.0 57.6

I think this has to do with making them global and the javelin not clearing them. How do i clear these values? I tried char = null; but then the program doesn't run. That's what i did in pc java you could set a object to null.

What can i do about this?

Thanks Johnny

Peter Verkaik · 2006-05-22 10:20

They shouldn't be placed after each other. Each loop a=0 before using bprintf()
so the char arrays are filled from position 0.
That should be visual if you run the V3 version I posted.
Here is my Jide Message output (I set passed=100 and disabled LCD output as I have no sensor)
using the attached program.

count: 1
·km/h: 72.0
·· km: 0000.000
count: 2
·km/h: 72.0
·· km: 0000.002
count: 3
·km/h: 72.0
·· km: 0000.005
count: 4
·km/h: 72.0
·· km: 0000.008
count: 5
·km/h: 72.0
·· km: 0000.011
count: 6
·km/h: 72.0
·· km: 0000.014
count: 7
·km/h: 72.0
·· km: 0000.017
count: 8
·km/h: 72.0
·· km: 0000.020
count: 9
·km/h: 72.0
·· km: 0000.023
count: 10
·km/h: 72.0
·· km: 0000.026
count: 11
·km/h: 72.0
·· km: 0000.029
count: 12
·km/h: 72.0
·· km: 0000.032
count: 13
·km/h: 72.0
·· km: 0000.035
count: 14
·km/h: 72.0
·· km: 0000.038
count: 15
·km/h: 72.0
·· km: 0000.041
count: 16
·km/h: 72.0
·· km: 0000.044
count: 17
·km/h: 72.0
·· km: 0000.047
count: 18
·km/h: 72.0
·· km: 0000.050
count: 19
·km/h: 72.0
·· km: 0000.053
count: 20
·km/h: 72.0
·· km: 0000.056
count: 21
·km/h: 72.0
·· km: 0000.059
count: 22
·km/h: 72.0
·· km: 0000.062
count: 23
·km/h: 72.0
·· km: 0000.065
count: 24
·km/h: 72.0
·· km: 0000.068
count: 25
·km/h: 72.0
·· km: 0000.071
count: 26
·km/h: 72.0
·· km: 0000.074
count: 27
·km/h: 72.0
·· km: 0000.077
count: 28
·km/h: 72.0
·· km: 0000.080
count: 29
·km/h: 72.0
·· km: 0000.083
count: 30
·km/h: 72.0
·· km: 0000.086
count: 31
·km/h: 72.0
·· km: 0000.089
count: 32
·km/h: 72.0
·· km: 0000.092
count: 33
·km/h: 72.0
·· km: 0000.095
count: 34
·km/h: 72.0
·· km: 0000.098
count: 35
·km/h: 72.0
·· km: 0000.101
count: 36
·km/h: 72.0
·· km: 0000.104
count: 37
·km/h: 72.0
·· km: 0000.107
count: 38
·km/h: 72.0
·· km: 0000.110
count: 39
·km/h: 72.0
·· km: 0000.113
count: 40
·km/h: 72.0
·· km: 0000.116
count: 41
·km/h: 72.0
·· km: 0000.119
count: 42
·km/h: 72.0
·· km: 0000.122
count: 43
·km/h: 72.0
·· km: 0000.125
count: 44
·km/h: 72.0
·· km: 0000.128
count: 45
·km/h: 72.0
·· km: 0000.131
count: 46
·km/h: 72.0
·· km: 0000.134
count: 47
·km/h: 72.0
·· km: 0000.137
count: 48
·km/h: 72.0
·· km: 0000.140
count: 49
·km/h: 72.0
·· km: 0000.143
count: 50
·km/h: 72.0
·· km: 0000.146
count: 51
·km/h: 72.0
·· km: 0000.149
count: 52
·km/h: 72.0
·· km: 0000.152
count: 53
·km/h: 72.0
·· km: 0000.155
count: 54
·km/h: 72.0
·· km: 0000.158
count: 55
·km/h: 72.0
·· km: 0000.161
count: 56
·km/h: 72.0
·· km: 0000.164
count: 57
·km/h: 72.0
·· km: 0000.167
count: 58
·km/h: 72.0
·· km: 0000.170
count: 59
·km/h: 72.0
·· km: 0000.173

As you can see, the values are not stored after each other.
That's why I asked to post your Jide Message output.
To pinpoint where it goes wrong, either in the char arrays
or the bprintf() methods.

regards peter

Peter Verkaik · 2006-05-22 10:55

I think you forgot to print a newline after printing a value.
My debug code does print a newline and then values are
not printed after each other, which proves the char arrays
only hold one value each loop.

regards peter

PlaneTeeR · 2006-05-22 11:03

This is the jide message output from v3

count: 1
km/h: 9.1
km: 0000.002
count: 2
km/h: 26.4
km: 0000.005
count: 3
km/h: 7.4
km: 0000.008
count: 4
km/h: 3.5
km: 0000.010
count: 5
km/h: 10.6
km: 0000.012
count: 6
km/h: 12.0
km: 0000.015
count: 7
km/h: 14.7
km: 0000.018
count: 8
km/h: 18.0
km: 0000.021
count: 9
km/h: 16.1
km: 0000.024
count: 10
km/h: 23.1
km: 0000.028
count: 11
km/h: 18.8
km: 0000.031
count: 12
km/h: 18.2
km: 0000.034
count: 13
km/h: 18.0
km: 0000.037
count: 14
km/h: 26.1
km: 0000.040
count: 15
km/h: 23.1
km: 0000.044
count: 16
km/h: 21.0
km: 0000.047
count: 17
km/h: 21.9
km: 0000.051
count: 18
km/h: 26.9
km: 0000.054
count: 19
km/h: 21.7
km: 0000.057
count: 20
km/h: 39.3
km: 0000.062
count: 21
km/h: 36.9
km: 0000.066
count: 22
km/h: 33.5
km: 0000.070
count: 23
km/h: 6.0
km: 0000.073
count: 24
km/h: 1800.0
km: 0000.182
count: 25
km/h: 78.2
km: 0000.189
count: 26
km/h: 24.1
km: 0000.193

Peter Verkaik · 2006-05-22 11:20

output looks ok.
I attached V5, which has an delay of 10 sec after LCD init
so you can make speed. Then a single loop is executed and
then the program halts after message "program finished".
Show me the jide message output and your lcd output.

regards peter

PlaneTeeR · 2006-05-22 12:03

The jide output:

count: 1
time: 880
km/h: 8.1
km: 0000.002
program finished
count: 1
time: 34
km/h: 211.8
km: 0000.002
program finished
count: 1
time: 98
km/h: 73.4
km: 0000.002
program finished
count: 1
time: 805
km/h: 8.9
km: 0000.002
program finished
count: 1
time: 306
km/h: 23.5
km: 0000.002
program finished
count: 1
time: 252
km/h: 28.6
km: 0000.002
program finished
count: 1
time: 390
km/h: 18.5
km: 0000.003
program finished

LCD all the same

Calculation goes wrong (Float32)

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