Help please with Assembly (PBPro user)

[wjsmarine]

Hi folks,
I've steered away from Assembly as long as I could but am stuck with an old Application Note (AN715) that is exactly what I need - problem is the code is only available in the pdf complete with a bunch of other stuff in the listing.

I copied this across to a text file and laboriously edited out all the line numbers, etc. but can only get the errors down to about 37 (using MPASM 5.03). I don't know anything about Assembly so don't have a clue how to get any further. Long term plans will be to learn this but so far PBP has proven to be everything I need for a long time now.

Rather than look like a complete idiot contacting Microchip I thought I'd ask the Guru's on the PBP list for some help.

If anyone can offer some suggestions on removing the last of these errors it would be very welcome. I'm sure this is obvious to the educated but I'm completely in the dark here.

Kind regards to all members.
Bill

[ScaleRobotics]

I am not so experienced at using assembly, but with the help of Darrel, I have been able to get two microchip asm examples to work. (Thanks Darrel!!!).

This example looks a little more straight forward, but then they always look easy, don't they?

First, you should define your variables. This I have always done outside the asm portion.


;example:
T1XHi VAR byte
T1XLo VAR byte
..................................etc


;When these variable are used inside asm, you add a little "_" on the front of them:
asm
.......... _T1XHi
........... _T1XLo

endasm


Why don't you start with that, and see how many fewer errors you get. Then post your errors here, and I will try to help you.

[wjsmarine]

Hi scalerobotics,
Thanks for the assistance, I'm sure there are a lot of users out there that are interested in this and will learn as well.

So are you saying instead of trying to assemble the list as I am, use PBP and paste it in between a Asm and Endasm statement, while declaring the variables up front before that? Or do you mean use _T1X, etc, in the listing without PBP?

Cheers,
Bill

[Acetronics2]

Hi, WJS



Rather than look like a complete idiot contacting Microchip I thought I'd ask the Guru's on the PBP list for some help.


You wouldn't look like an idiot posting your query on Microchip users Forum ... And you could find people having played with this AN before ... Eventually used to asm too, ...

NOW ... browsing the Parallax site, you could discover ( oh surprise ! ) that they have a Memsic 2125 accelerometer , with Application examples AND BS2 Code ...

Knowing the 2125 works in the PWM way like the adsl 202, AND BS2 code, which is PbP COMPATIBLE ...

Why are you still sllepingly staring at that post ....

Hurry up !!! ... LOL

Alain

[ScaleRobotics]

So are you saying instead of trying to assemble the list as I am, use PBP and paste it in between a Asm and Endasm statement, while declaring the variables up front before that? Or do you mean use _T1X, etc, in the listing without PBP?

Hello Bill,

From your previous post, it sounded like you were happy with the speed of programming with pbp, and that it could do almost everything you wanted. We should be able to get your tilt.asm working with pbp as an include file, which would let you add you own code in pbp and get the tilt sensor doing something useful.

To start with, you will need to define the variables. (of course, you will have to start with defining the osc, your ports, etc, just as you always do). I define the variables inside pbp, which lets them be used within the pbp, as well as the asm portions of your code. When you do this:

T1XHi VAR byte
T1XLo VAR byte

inside your asm, the variables need to look like this:
asm
movwf _T1XHi
movf _T1XLo, W
endasm

You can look at my first conversion as an example. This assembly used object code, and yours does not. That's why I think it will be a little easier. Check out:
http://www.picbasic.co.uk/forum/showthread.php?t=7502


Your code looks interesting. Would be glad to help if you decide to proceed.

Walter

[wjsmarine]

Hi Walter,

Thanks for the help. I'm going to have to work on this in the background unfortunately because of a sudden unexpected pile of work which has just descended (meaning from Above, if you know what I mean!) onto me. I'll get back to you as soon as I can clear some of the work and have some news. Thanks also for the link to your previous effort, very informative.

Thanks Acetronics for the pointer - I'll take a look but I think it best for my education to persist with the asm challenge as no doubt there will be other times when I will need to do something similar with asm code I come across.

Kind regards to all.
Bill

[ScaleRobotics]

I looked a little more at the assembly code you attached to your post. One drawback, it uses LCD code that is written for 4 mhz crystal which makes it a bit less flexible. This could be edited out and more code written for pbp, to be flexible for use with different pics. By the time you do that, maybe Alain is right, better to use code that is written in picbasic.

I looked at the parallax code, like Alain suggested. They are using a lookup table with a pulsin command. This could be done pretty easily. If you want to make it more exciting, you could use an tan-1 or arctan function. Oh, but picbasic does not have an arctan function you might say.... True, but Darrel helped me get a atan2(y,x) function working, and atan2(y,1) is the same as the tan-1 or arctan function!

What am I talking about?
Well, I did a few searches on angle tilt and got to Freescale Semiconductors AN3461
http://www.freescale.com/files/sensors/doc/app_note/AN3461.pdf

And they mention using the arctan function to determine the angle:

theta = tan-1 (Ax/Az) and I believe that angle of Y = tan-1(Ay/Az)

A lookup table for the 10 bit a/d converter would be a bit long. And we can have resolution of about .3 degrees with a 10 bit tilt sensor value. (I know your tilt sensor does not work on A/D converter, but rather pulse width, but you could still use this formula).

Here is the atan2 code:
http://www.picbasic.co.uk/forum/showthread.php?t=10528

I will try to show an example in the next couple days.

[ScaleRobotics]

Here is some code to determine tilt using at least a two axis accelerometer. It uses trig.inc
This does not do the a/d conversions, or pulse measurement conversions, that would have to be added.



define OSC 20
'code working with PIC-MT-USB
include "TRIG.inc"

main:
define LED PortD.3

DEFINE LCD_DREG PORTD ; Set LCD Data port B C D
DEFINE LCD_DBIT 4 ; Set starting Data bit (0 or 4) 4 0
DEFINE LCD_RSREG PORTD ; Set LCD Register Select port A A
DEFINE LCD_RSBIT 0 ; Set LCD Register Select bit 3 2
DEFINE LCD_EREG PORTD ; Set LCD Enable port A A
DEFINE LCD_EBIT 2 ; Set LCD Enable bit 1 5
DEFINE LCD_BITS 4 ; Set LCD bus size (4 or 8 bits) 4 4
DEFINE LCD_LINES 2 ; Set number of lines on LCD 2 2
define LCD_RWREG PORTD
define LCD_RWBIT 1
ADCON1=15

TRISA=%00000011 ' Set PORTA 0-1-3 used for AD
TRISB=%00000000 ' Set PortB
TRISC=%00000000
TRISD=%00000100
' Vdd 5 volts
' Vss Ground
' Vo 20K potentiometer (or ground)
' DB0-3 No connect

a var word
xresult var word 'result of accelerometer sensor in x axis
yresult var word 'result of accelerometer sensor in y axis
zresult var word 'result of accelerometer sensor in z axis
correct var bit 'able to keep equation the same, and flip angle
xdir var bit 'shows direction of x tilt
ydir var bit 'shows direction of y tilt
zdir var bit 'shows direction of z tilt


Lcdout $fe, 1 ' Clear LCD screen
Pause 500 ' Wait for LCD to startup
toggle portD.3

xresult = 553 'is 41 away from center
zresult = 297 'is 215 away from center
'to try it on your calculator tan^-1(41/215) = 10.796543 degrees
'xresult is acceleration allong the x axis
if xresult > 512 then 'get difference from neutral to gravity reading
xresult = xresult - 512 'since we are using 10 bit result, half is 512
xdir = 0
else 'accelerometer reads 512 with no gravity
xresult = 512 - xresult 'and above or below depending on direction tilt
xdir = 1
endif

if yresult > 512 then 'yresult is acceleration allong the y axis
yresult = yresult - 512
ydir = 0
else
yresult = 512 - yresult
ydir = 1
endif

if zresult > 512 then 'zresult is acceleration allong the z axis
zresult = zresult - 512
zdir = 0
else
zresult = 512 - zresult
zdir = 1
endif

if xresult < zresult then 'if x/z is < 1 then x/z
xresult = xresult * 30000 'we will have to correct angle if this is case
y = div32 zresult
correct = 0
else
zresult = zresult * 30000 'else z/x to keep our equation within limits
y = div32 xresult
correct = 1
endif
x = 30000 'multiply this by same value 30000 as above
call atan2
if correct = 0 then y = 9000 - y '90.00 degrees - y = corrected angle

lcdout $FE,1,#y/100,".",#y//100," degrees" 'y = angle 1080 = 10.80 degrees
lcdout $FE,$C0,"x=",#xdir," y=",#ydir," z=",#zdir
end


here is the location of the trig.inc file

http://www.picbasic.co.uk/forum/attachment.php?attachmentid=3204&d=1234739854

[ScaleRobotics]

There was a bug in my above code, which (with my hardware) showed up between 40 and 50 degrees tilt. I was multiplying with too large a number that either a word in TRIG.INC, or a 31 bit div32 could handle. Changing the div32 equations from 30,000 to 10,000 did the trick. With a 3 axis sensor, it must be calibrated horizontal (for x and Y) and then in a position that puts Z in a horizontal position. Here is some code that worked pretty well for me using Olimex's PIC_LCD3310 with the built in MMA7260 g sensor. The math gives degreess out in a dddd format which really equals dd.dd. However, with a 10 bit result from ADC, the math is accurate to about 0.3 degrees. This version calibrates x and y, and then z, when it is first turned on, and averages 6 samples. It also shows left, right, up and down tilt, as well as whether it is inverted or not.



loop:
zave = 0
xave = 0
yave = 0
for nn = 0 to 5 'takes average of nn adc results
ADCON0.2 = 0
ADCON0.3 = 0 'Channel select bit CHS1(should already be a 0)
gosub adconvert
zresult = adval
zave = zave + zresult
ADCON0.2 = 1
ADCON0.3 = 0 'Channel select bit CHS1(should already be a 0)
gosub adconvert
xresult = adval
xave = xave + xresult
ADCON0.2 = 0
ADCON0.3 = 1 'Channel select bit CHS1(should already be a 0)
gosub adconvert
yresult = adval
yave = yave + yresult
next nn

zresult = zave/6 'divide averaged sum by nn
xresult = xave/6
yresult = yave/6

@ PrintVar 16,0, _zresult
@ PrintVar 16,1, _xresult
@ PrintVar 16,2, _yresult

if startbit = 0 then 'calibrate routine - only does at first startup
'first hold horizontal for first set of calibration for x and y
xcal = xresult
ycal = yresult
@ PrintStr 0,0, "HOLD VERTICAL UNTIL MESSAGE DISSAPEARS"
'then hold vertical to calibrate z sensor
pause 5000
ADCON0.2 = 0
ADCON0.3 = 0 'Channel select bit CHS1(should already be a 0)
gosub adconvert
zresult = adval
zcal = zresult
gosub Lcd_Clear
@ PrintStr 0,0, "Z= " ;display on Nokia 3310
@ PrintStr 0,1, "X= "
@ PrintStr 0,2, "Y= "
@ PrintVar 48,0, _zcal
@ PrintVar 48,1, _xcal
@ PrintVar 48,2, _ycal
startbit =1
endif

if xresult > xcal then 'get difference from neutral to gravity reading
xresult = xresult - xcal 'since we are using 10 bit result, should be around 512
xdir = 0
else 'accelerometer reads 512 with no gravity
xresult = xcal - xresult 'and above or below depending on direction tilt
xdir = 1
endif

if yresult > ycal then 'yresult is acceleration allong the y axis
yresult = yresult - ycal
ydir = 0
else
yresult = ycal - yresult
ydir = 1
endif

if zresult > zcal then 'zresult is acceleration allong the z axis
zresult = zresult - zcal
zdir = 0
else
zresult = zcal - zresult
zdir = 1
endif

angletosolve = xresult
gosub solveangle

adval = y/100
@ PrintStr 0,5, " X DEGREES"
if xdir = 1 then
@ PrintStr 0,5, "U" 'tilted upward from level
else
@ PrintStr 0,5, "D" 'tilted down
endif
@ PrintVar 8,5, _adval

angletosolve = yresult
gosub solveangle

If zdir = 0 then
@ PrintStr 0,3, "INVERTED" 'upside down
else
@ PrintStr 0,3, "NORMAL " 'right side up
endif

adval = y/100
@ PrintStr 0,4, " Y DEGREES"
if ydir = 1 then
@ PrintStr 0,4, "L" 'tilted left
else
@ PrintStr 0,4, "R" 'tilted right
endif
@ PrintVar 8,4, _adval
goto loop

adconvert: ADCON0.1 = 1 'Start ADC Conversion
notdone: pause 5
if ADCON0.1 = 1 Then notdone 'wait for low on bit-2 of ADCON0
adval.highbyte = ADRESH 'move HIGH byte of result to adval
adval.lowbyte = ADRESL 'move LOW byte of result to adval
'Pause 10 'Wait .1 second
return

solveangle:
'**********Solve for x angle ********************************************
if angletosolve < zresult then 'if x/z is < 1 then x/z
dummy = angletosolve * 10000 'we will have to correct angle if this is case
y = div32 zresult
correct = 0
else
dummy = zresult * 10000 'else z/x to keep our equation within limits
y = div32 angletosolve
correct = 1
endif
x = 10000 'multiply this by same value 10000 as above
call atan2
if correct = 0 then y = 9000 - y '90.00 degrees - y = corrected angle
'************************************************* ***********************
return

[ScaleRobotics]

After seeing some odd behavior while rotating the accelerometer, I eventually noticed that in the formula I used, an assumption is made that rotation is ideal around the y axis. So as long as you have x rotation but not y, it works, or y rotation, but not x, it works. But if you have a combination of both, it did not give you correct values.

Time for a new equation. The good news was, the same data sheet that showed me the "ideal" equation had an example of the equation I wanted.

http://www.scalerobotics.com/tilt.jpg

http://www.freescale.com/files/sensors/doc/app_note/AN3461.pdf

This equation required longs, and a few other adjustments. It seems to be pretty accurate, though I have not come up with an easy way to test it.
I have included TRIGL.INC, which has a minor edit to run with pbpl.


http://www.youtube.com/watch?v=PFVfjWyK9vs

Here is the meat of the code:



solveangle:
'**********Solve for x angle ********************************************
if xresult < yresult + zresult then
dummy = 5000 'when x is smaller the following equation works best
xlong = (dummy * xresult) /(sqr((yresult*yresult) + (zresult*zresult)))
else 'keeps results accurate at near 0 and near 90 degree values
dummy =30 'when x is larger the following equation works best
xlong = (dummy * xresult*xresult) / ((yresult*yresult)+(zresult*zresult))
endif
y = xlong
x = dummy 'Assign x and y values for atan2 function
call atan2
xangle = 9000 - y

if yresult < xresult + zresult then
dummy = 5000 'when y is smaller the following eqauation works best
ylong = (dummy * yresult) / (sqr((xresult*xresult) + (zresult*zresult)))
else
dummy =30 'when y is larger the following equation works best
ylong = (dummy * yresult*yresult) / ((xresult*xresult)+(zresult*zresult))
endif
y = ylong
x = dummy '
call atan2
yangle = 9000 - y