using the sin function in ccs c compiler for pic 16f877a

[ft]

hey everyone !!

i have a problem using the sin or cos function in my program. when ever i use the sin or cos function in my program, the while program stops working and nothing is displayed the way it should be. however if i use the exp() function in the same place .then no problem occurs. there is no issue with rom or ram. this problem is really baffling, if any one has any idea, please do reply

thanks

[PCM programmer]

Here's a test program. Try it. I compiled it with PCH vs. 3.188
and it displayed the following correct result:

result = 1.000000

[ftsame]

thankyou for your reply.

the thing is that if i use just the sin function in a separate program , it works fine, but in my specific program it just does not work, i dont know why, not only that but the rest of the program which works fine before the inclusion of sin , also seizes to work. other maths functions like 'exp' work fine. there is this problem with sin function. is there any ram or rom issues with sin or something

this problem is really buggin me,
please help

ft

[Ttelmah]

Not particularly.
It uses a significant amount of RAM (about 40bytes in the worst case), and a lot of ROM (about 1700 bytes). Unless you are short of either, or are manually using memory addresses, this should not be a problem. Obvious things would be that sin also takes a significant amount of time, and if (for instance), there is some floating point arithmetic in an interrupt function, though the memory used by this should be protected, the possibility does arise of a problem here. Also if the processor was close to a watchdog 'timeout', the time needed for this, might cause a reset to occur.

Best Wishes

[ftsame2]

thanx again for your reply.

well i am not using a watch dog timer.nor am i using interrupts. what i am doing is using "calloc" and "free" commands to allocate and free memory for a pointer to the array. also there shouldnt really be any problem with the rom and ram as there is plenty left. also the "exp" command seems to work with out a problem in the same place where the sin command doesnt work.


plz help

[Ttelmah]

Exp, uses about the same amount of ROM (slightly more if I remember correctly), but a _lot_ less RAM (only about 10 bytes). I think it points to RAM memory management as the problem. Have you got '#device *=16' near the start of your program (the line after loading the processor include file)?. Otherwise you are only able to access the first bank of RAM, and could be getting problems with the memory management, functions (which assume this is set).

Best Wishes

[ftsame3]

thank you for your advice Ttelmah, the sin is now working, but there is another problem now belive it or not. the thing is that the whole program is working only once, that is now i have to reset the microcontroller everytime to make it work. in my program i am dynamically allocating memory by using "ptr=calloc(62,1)". and then freeing up that memory at the end of 'while(1)' by doing "free(ptr)". can u plz help me again, so that the whole program keeps working over and over as it was before i used "device *=16" and "sin(x)".


thankyou for your useful guidance once again

ft