# Assembly Language Routines

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• 20th May 2012, 21:51
internetuser2k11
Assembly Language Routines
Hi!

I am looking for PIC asm routines for

Conversions
Long Integer to String (Long Integer - 4bytes)
Double to String (Double - 4bytes)

Floating Point Math

SUB
MUL
DIV
Square
Square root
power

I want to calculate numbers like 24.2874353903764903627393 * 5.527932455274853690390.

display

output string to lcd.
• 20th May 2012, 23:47
Re: Assembly Language Routines
• 21st May 2012, 04:43
internetuser2k11
Re: Assembly Language Routines
Can I use this for getting 4 byte variable routines?

http://avtanski.net/projects/math/
• 22nd May 2012, 08:00
Re: Assembly Language Routines
You have to try to see the results.
• 22nd May 2012, 09:20
DineshSL
Re: Assembly Language Routines
In assembly, there is no concept of conversions between Strings, integer, Long, short. In high level languages that concepts is there by restricting mathematical manipulating of variables.
In assembly it's only memory register that you store data and you are free to manipulate them as you wish (using assembly instructions). You may store 0x48, 0x45, 0x4c, 0x4c, 0x4f in 5 registers and you can add them together or consider them as ASCII values and get the word "HELLO" on a LCD.

However you may write functions in assembly for data manipulations (eg. convert ASCII values of small-letters to uppercase, add multi-register values, get decimal representation of a register value...) but conversion between variable types is not there.

Use a good book on assembly;I hope you can get the idea.
• 22nd May 2012, 10:30
internetuser2k11
Re: Assembly Language Routines
The problem is, I am readind through adc. The byte value I get in ADRESH and ADRESL (12-bit) have to be converted to Decimal value and then converted to ascii for displaying in lcd. Give some names of assembly books.
• 22nd May 2012, 10:54
jpanhalt
Re: Assembly Language Routines
On the Piclist site referenced above, there is a whole section on radix conversion: http://www.piclist.com/techref/micro...adix/index.htm

There are routines to go from binary 12 or 16 bit to BCD as well as from binary directly to ASCII decimal.

John
• 22nd May 2012, 11:22
internetuser2k11
Re: Assembly Language Routines
I need to do floating point multiplication and division on adc value. The resulting floating point value has to be converted to ascii for lcd display.
• 22nd May 2012, 11:45
jpanhalt
Re: Assembly Language Routines
That is not quite what you described needing in post#6.

It appears now that you want to do math and multiply a 24-digit decimal by 22-digit decimal in floating point based somehow on results from 12-bit ADC. The max resolution that can produce is 1 part in 4096. The rest of the digits in your 24-digit number are meaningless.

At this point, I think the best way for you to get meaningful help is to describe what it is you are trying to do in more detail. Are you sure you need floating point? Why? For example, if you need the remainder from a division, say to 4 decimal precision, you may be able to avoid floating point by simply left shifting the dividend to the left by two or more bytes. Then strip (concatenate) the insignificant bits from the result later on.

John
• 22nd May 2012, 12:21
internetuser2k11
Re: Assembly Language Routines
12-bit gives 4095 digital count. I've to multiply 4095 by some no. like 0.5346. Then I get some result. Then there are some similar divisions and multiplications. The final result will be some hex value in the register. I need to convert that into decimal and display it on lcd.
• 22nd May 2012, 12:41
jpanhalt
Re: Assembly Language Routines
The precision of your result is still limited by the precision of your ADC. Try to visualize your result, if the ADC only gave 1-bit precision (i.e., 0 or 1), or to avoid zero, try 2-bit precision.

It is still not clear why you need floating point, as it appears the manipulations are known beforehand and the only data entry is the ADC value. Have you considered using tables? If you are certain you need floating point point, have you seen this?

http://www.codeproject.com/Articles/...ing-Point-Type

John
• 22nd May 2012, 12:44
sky_123
Re: Assembly Language Routines
There is a reason most people use C instead of assembler. Imagine having to write a whole load of floating point functions, and then someone changes
their mind, and wants to use AVR instead of PIC. And then changes mind again to ARM.
Better to use C if you want to do a lot of floating point, unless you can use lookup tables or scale up and do non-floating point as mentioned above.
• 22nd May 2012, 12:57
internetuser2k11
Re: Assembly Language Routines
OK. Tell me how to do 32h * 5h / FFFh?
• 22nd May 2012, 13:55
sky_123
Re: Assembly Language Routines
You do know that equals zero, right? or 0.xxx... if you're not constrained to integers.
If that's a calculation you need to do often, then you can pre-calculate and store in a look-up table
to whatever accuracy you desire.
For example, if you need to multiply numbers in the range of 0 to 100 by 5 and then divide by FFF,
then do that for all 100 numbers, and store the results. Then you look them up.
If you don't have space for a look-up table for all your calculations, then you could use external
flash, you can get it in small packages with SPI interface for example.
Or, use C and use a math library.
• 22nd May 2012, 14:05
internetuser2k11
Re: Assembly Language Routines
I get my adc values from 0000h to 0FFFh. I have to multiply it by 0005h and divide by 4095h. I get some value, which is the resistance of a device. Depending upon the resistance, I've to calculate its temperature using 2 polynomial equations. I've done that in mikroC, but I am implementing it in pic asm.

• 22nd May 2012, 14:15
sky_123
Re: Assembly Language Routines
Right.. you're just scaling by a factor (i.e. 5/FFFh), nothing non-linear, so this is easier.
Technically you don't even need a lookup table. But here's the concept if you used one.
Perform the calculation for values from 0 to FFF, and store them (i.e. 0.0012, 0.0024, etc)
but scaled up, e.g. 1, 2 if you want it to 3 decimal places, i.e. I've multiplied by 1000.
Make sure the table results are scaled up so that you're not dealing with decimal points.
If you want to continue doing further calculations, then you can use the scaled values.
If you want to display the results, then you know to scale back down by moving the decimal point.
The benefit of a look-up table is that it will save you compute time if you've got nonlinear
values. For the linear case, note that you could just multiply the single scaled value.
And a multiply is just 'add' instructions in a loop, if you're using an assembler.
• 22nd May 2012, 15:09
internetuser2k11
Re: Assembly Language Routines
But when I use the polynomial with the resistance, I will be taking squares and square roots of some constant coefficients.
• 22nd May 2012, 16:21
sky_123
Re: Assembly Language Routines
So when you're using square roots, then this is absolutely a good use-case for a look-up table. Squares can be composed of multiple additions,
so you could use a loop and 'ADD' instruction in assembler. It will perform the square. Or to save time, use a look-up table for that too.
If you don't want to use a look-up table for square roots, then you need to find an algorithm (math book) and implement in assembler.
At some stage, you'll possibly decide that a math library is easier, and just move to C, or you'll dedicate memory for a lookup table.
Since your original problem is to use a temp probe and convert the value to a temperature, you'd save an awful lot of time just getting the
table of resistance values from the probe vendor and sticking it (or a conversion) in a lookup table. But it's your choice.
• 22nd May 2012, 18:05
internetuser2k11
Re: Assembly Language Routines
My equation is (-a + (sqrt(a^2 - 4b(1-x/xo)))/2b and const1 * x + const2 * x^2 -const3 * x^3 - const4 * x^4 + const5 * x^5. I've to implement it in asm. In mikroC double data type is 4 bytes, but I don't know how to perform math operations in asm. Should I use variables of 4 bytes in mpasm and perform the math operations. I know that operations will be performed in hex. I have to convert the resulting hex value to decimal. But how do I get values like 8.4168. How to get the decimal part from the hex value. I'm using pic18. the registers are 1 byte. If I have 3 operands of 4 bytes size, how to move the value of 4 byte to i byte w reg for performing operations?
• 22nd May 2012, 19:45
sky_123
Re: Assembly Language Routines
Honestly, I think it won't be possible, unless you can find by luck some floating point math libraries for your device.
It is a lot of work to implement it from scratch, especially if you're not familiar with this.
I say give up, and store a lookup table of the ADC value and the corresponding temperature.
If you can't do that due to lack of space, then change to a different PIC with more space, or external memory, or
switch to C and use a math library. Simple!
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