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I am a newbee in Microcontroller programing . the code I have written in C was from a book and it is giving linker error. please help me to solve the problem. I am sending the code:
/*reading pwm waveform and calculation of frequency using microcontroller*/ #include<reg52.h> sbit RS=P2^0; sbit RW=P2^1; sbit EN=P2^2;
sbit IN=P2^4;
void delay(void); void INIT(void); void ENABLE(void); void LINE(int);
int ONTIME(int); int offtime(int); /*declaration of functions complete*/ // void LINE(int i) { if(i==1) { RS=0; RW=0; P1=0x80; ENABLE(); RS=1; } else { RS=0; RW=0; P1=0xC0; ENABLE(); RS=1; } }
/*dealy subroutine*/
void delay(void) { int i,j; for(j=0;j<10;j++) { for(i=0;i<100;i++); } }
/*delay complete*/
/*Enable subroutine*/ void ENABLE(void) { EN=1; delay(); EN=0; delay(); }
/*initialisation of LCD giving proper command*/
void INIT(void) { RS=0; RW=0; EN=0; P1=0x38;// 2 Lines and 5*7 matrix LCD ENABLE(); ENABLE(); ENABLE(); P1=0x06; // Shift cursor to left ENABLE(); P1=0x0E; //display on, cursor blinking ENABLE(); P1=0x01; //clear display screen ENABLE(); } /* measuring ontime*/ int ONTIME(int m) { if(m==1) { IN=1; /*input to 8051 is from 555 osc*/ TMOD=0x01; TR0=0; TF0=0; TL0=0x00; TH0=0x00; while(IN); /*check for rising edge*/ while(!IN); TR0=1; while(IN); TR0=0; }
/* TO MEASURE OFFTIME*/
if(m==2) { IN=1; TMOD=0x01; TR0=0; TF0=0; TL0=0x00; TH0=0x00;
while(!IN); // check for falling edge while(IN); TR0=1; while(!IN); // CHECK FOR RISING EDGE TR0=0; } return((TH0*256)+TL0); }
void main(void) { int unit, tens, hundred, thousand, tenthou, x; char code dis3[]="Fre in HZ="; char *p; int i,j,k,freq,l; while(1) { for(x=1;x<=3;x++) { if(x==1) { i=ONTIME(x); k=i; }
if(x==2) { i=offtime(x); l=i; } if(x==3) { freq=k+1; i=1/freq; } }
unit=(i%10); tens=(i/10)%10; hundred=(i/100)%10; thousand=(i/1000)%10; tenthou=(i/1000)%10; unit=unit+0x30; tens=tens+0x30; hundred=hundred+0x30; thousand=thousand+0x30; tenthou=tenthou+0x30; INIT(); LINE(0);
p=&dis3;
for(j=0;j<8;j++) { P1=*p++; ENABLE(); }
LINE(2); P1=tenthou; ENABLE(); P1=thousand; ENABLE(); P1=hundred; ENABLE(); P1=unit; ENABLE(); } }
I have recopied it
/*reading pwm waveform and calculation of frequency using microcontroller*/ #include<reg52.h> sbit RS=P2^0; sbit RW=P2^1; sbit EN=P2^2; sbit IN=P2^4; void delay(void); void INIT(void); void ENABLE(void); void LINE(int); int ONTIME(int); int offtime(int); /*declaration of functions complete*/ void LINE(int i) { if(i==1) { RS=0; RW=0; P1=0x80; ENABLE(); RS=1; } else { RS=0; RW=0; P1=0xC0; ENABLE(); RS=1; } } /*dealy subroutine*/ void delay(void) { int i,j; for(j=0;j<10;j++) { for(i=0;i<100;i++); } } /*Enable subroutine*/ void ENABLE(void) { EN=1; delay(); EN=0; delay(); } /*initialisation of LCD giving proper command*/ void INIT(void) { RS=0; RW=0; EN=0; P1=0x38;// 2 Lines and 5*7 matrix LCD ENABLE(); ENABLE(); ENABLE(); ENABLE(); P1=0x06; // Shift cursor to left ENABLE(); P1=0x0E; //display on, cursor blinking ENABLE(); P1=0x01; //clear display screen ENABLE(); } /* measuring ontime*/ int ONTIME(int m) { if(m==1) { IN=1; /*input to 8051 is from 555 osc*/ TMOD=0x01; TR0=0; TF0=0; TL0=0x00; TH0=0x00; while(IN); /*check for rising edge*/ while(!IN); TR0=1; while(IN); TR0=0; } /* TO MEASURE OFFTIME*/ if(m==2) { IN=1; TMOD=0x01; TR0=0; TF0=0; TL0=0x00; TH0=0x00; while(!IN); // check for falling edge while(IN); TR0=1; while(!IN); // CHECK FOR RISING EDGE TR0=0; } return((TH0*256)+TL0); } void main(void) { int unit, tens, hundred, thousand, tenthou, x; char code dis3[]="Fre in HZ="; char *p; int i,j,k,freq,l; while(1) { for(x=1;x<=3;x++) { if(x==1) { i=ONTIME(x); k=i; } if(x==2) { i=offtime(x); l=i; } if(x==3) { freq=k+1; i=1/freq; } } unit=(i%10); tens=(i/10)%10; hundred=(i/100)%10; thousand=(i/1000)%10; tenthou=(i/10000)%10; unit=unit+0x30; tens=tens+0x30; hundred=hundred+0x30; thousand=thousand+0x30; tenthou=tenthou+0x30; INIT(); LINE(1); p=&dis3; for(j=0;j<8;j++) { P1=*p++; ENABLE(); } LINE(2); P1=tenthou; ENABLE(); P1=thousand; ENABLE(); P1=hundred; ENABLE(); P1=tens; ENABLE(); P1=unit; ENABLE(); } }
the error is
Build target 'Target 1' compiling pwm waveform.c... linking... *** WARNING L1: UNRESOLVED EXTERNAL SYMBOL SYMBOL: _OFFTIME MODULE: pwm waveform.obj (PWM_WAVEFORM) *** WARNING L2: REFERENCE MADE TO UNRESOLVED EXTERNAL SYMBOL: _OFFTIME MODULE: pwm waveform.obj (PWM_WAVEFORM) ADDRESS: 082CH Program Size: data=32.0 xdata=0 code=747 "PWM waveform reading using microcontroller" - 0 Error(s), 2 Warning(s).
Did you write this code? I doubt that very much! Otherwise, you would have seen that you don't have a function called "offtime" in your code thus the linker error!
No; he didn't - he says he got it from a book!
As noted previously,
"Maybe you similarly missed some important instructions in the book...?"
Does appear to be the case!
Another example that just copying code is not enough - you have to understand it! See: http://www.keil.com/forum/19129/
And have you bothered to look-up the description of that error in the Manual yet?
Again, here is the link: http://www.keil.com/support/man/docs/bl51/bl51_l1.htm
he says he got it from a book!
I'll say it again: if you are not capable of writing a given code yourself, it serves no purpose to get it from elsewhere. "transfer of code" invariably will result is something not working and if you are not capable of writing the code yourself, you will be totally lost trying to make the 'found' code work. However, it can sometimes be a shortcut to grab some code and fix it rather than starting from scratch.
Erik
If you found that in a book, throw it away and get a better one.
you are right. I have corrected the error. thank you very much
"that" refers to using 'for' loops for timing.
Do not rely on 'for' loops - or, indeed, any othe HLL construct - for timing!
See: www.8052.com/.../182476 And: www.8052.com/.../162556 and many, many more...
""transfer of code" invariably will result is something not working"
that may be a little bit too strong, don't you think?
A little - but not nuch!
Especially with embedded code, it does tend to be so very specific to a particular target & environment that expecting any random piece of cut-&-paste code to "just work" is wishful thinking in the extreme!
"Especially with embedded code, it does tend to be so very specific to a particular target & environment that expecting any random piece of cut-&-paste code to "just work" is wishful thinking in the extreme!"
exaggerated truth is a lie.
sure, there is a degree of hardware dependency in any code, more in embedded than others. but that does not mean one piece of code written for one target cannot work for another hardware, unmodified or slightly modified (to use different header files for example).
this is particularly true if your code is written with a logic structure and with portability in mind.
"Do not rely on 'for' loops - or, indeed, any othe HLL construct - for timing!"
it depends on what the timing requirements are.
sometimes, you don't need precise timing, or allow for large timing errors in one direction, it makes perfect sense to use simple delay loops in those cases.
again, it is impossible to lay down a general rule, other than that you need to look into the specific applications to determine what is the best / better approach.
But there is this one general rule: An incorrectly written for-loop delay can be totally removed by the compiler resulting in zero delay.
The posted code is without side effects so the OP is throwing a dice.
You are missing out on an important ghing. When debating with beginners, it's way better to start with absolutes. Special cases are better debated at a later time, when the person have enough experience and knowledge to fully understand the details. Doing it your way means that the unexperienced developer will very, very often think: "But my code is probably so special, so I should be fine going the alternative route." And the person whill be much more hurt than first getting a truth in absolute terms and years later receiving a more modulated answer.
If you had spent any real time reading enough thousands of threads, you would have noticed the number of people who are constantly burned by software delays just because they are too often seeing software delays and too often hearing people talking about software delays.
"An incorrectly written for-loop delay can be totally removed by the compiler resulting in zero delay."
but that's not the issue with the delay loop itself: it is an issue with documentation or user education.
it is very much like electricity: incorrectly used, it can kill you. But that doesn't mean that you don't use electricity. instead, you put warning signs on the sockets and you educate the users.
the same thing here.
and the issue (of documentation / education) exists with any approach. You can write a piece of code using any approach you like and I can tweak the rest of the code to mess it up.
No, it doesn't.
The timing associated with HLL constructs can never be relied upon.
"No, it doesn't."
what doesn't what?
"The timing associated with HLL constructs can never be relied upon."
the only thing that cannot be relied upon is a stupid blanket statement made by people with tunnel vision, like the above.