hi, i've got a problem when using log10(...) or log(...) from math.h . e.g. log10(10) doesn't return 1 but something like 3.1... e+015. does anyone have an idea what could be the reason for this? thx j.w.
I'd suggest running the program on the target rather than the simulator and printf() the value out of the serial port. I tried this with your program and it gave the correct result, but the simulator gave 3.5xxxx e-43. I've been using Keil for years and still can't get the simulator to work. But then, I haven't read the manual. Stefan
If you are having problems on the simulator it may be for reasons that Mike points out. The log10 function works for me in the sumulator but I made sure I stored the result in a volatile floating point variable so I knew it would not get optimized out. Using the variable in a printf statement after calling log10 should also do the trick. -Walt
Walt, I even tried this: float x,y; x=log10(10); printf("%f",x); y=x; printf("%f",x); breaking on the y=x line still gave garbage for x, however the printf() statements worked fine. Stefan
Hi Stefan, Very strange, I copied and pasted your code into a file and simulated it and it works fine for me. The line y=x; gets optimized out but x contains the value 1 and both printf's output 1.00000. -Walt
Uhh, You still don't use y in your program. The C51 IS an optimizing compiler. Jon
Well, I've no idea what's going on now. I created a new project, pasted the code into it and it now works fine in the simulator. An odd thing though, I have optimisation level 11 selected and in my case y doesn't seem to be optimised out: .cod: ----- FUNCTION main (BEGIN) ----- FILE: 'junk.c' 27: void main(void) 28: { 29: float x,y; 30: 31: Setup(); 000C48 9132 ACALL Setup 32: 33: x=log10(10); 000C4A 7F00 MOV R7,#00H 000C4C 7E00 MOV R6,#00H 000C4E 7D20 MOV R5,#020H 000C50 7C41 MOV R4,#041H 000C52 5173 ACALL _log10 000C54 8F25 MOV x+03H,R7 000C56 8E24 MOV x+02H,R6 000C58 8D23 MOV x+01H,R5 000C5A 8C22 MOV x,R4 34: printf("%f",x); 000C5C 7BFF MOV R3,#0FFH 000C5E 7A0C MOV R2,#HIGH 01000C2FH 000C60 792F MOV R1,#LOW 01000C2FH 000C62 8F30 MOV ?_printf?BYTE+06H,R7 000C64 8E2F MOV ?_printf?BYTE+05H,R6 000C66 8D2E MOV ?_printf?BYTE+04H,R5 000C68 8C2D MOV ?_printf?BYTE+03H,R4 000C6A 120636 LCALL _printf 35: y=x; 000C6D 852529 MOV y+03H,x+03H 000C70 852428 MOV y+02H,x+02H 000C73 852327 MOV y+01H,x+01H 000C76 852226 MOV y,x 36: printf("%f",x); 000C79 7BFF MOV R3,#0FFH 000C7B 7A0C MOV R2,#HIGH 01000C2FH 000C7D 792F MOV R1,#LOW 01000C2FH 000C7F 852530 MOV ?_printf?BYTE+06H,x+03H 000C82 85242F MOV ?_printf?BYTE+05H,x+02H 000C85 85232E MOV ?_printf?BYTE+04H,x+01H 000C88 85222D MOV ?_printf?BYTE+03H,x 000C8B 020636 LJMP _printf ----- FUNCTION main (END) ------- Stefan