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zipmmcs
Joined: 03 Feb 2008
Posts: 2
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| Measuring time |
 Posted: Tue Jun 10, 2008 3:56 pm |
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Hello,
I'm new in PIC programming, so please forgive me for the potential silly and obvious failures.
I'd like to measure frequency, especially RPM. I looked into the topics that are about this issue, but I could not implement them to my application, so I started to write my own one.
I'm using an 16F873 with 4MHz Crystal, but later I want to implement the code to an 16F628 (but the latter is not ICD compatible so I needed a more confortable one).
I'd like to measure the frequency on the RA4 pin, and I'm using 2pcs of TIL311 to display (that's why I'm cutting off the least 2 digits and translating the decimal numbers to dcb).
The only thing I know, that the frequency measuring is not working - the others are ok.
How should I modify the code? I think I declared everything fine, but...
Please give me soma advice!
| Code: | #include <16F873.h>
#device *=16
#FUSES XT, NOPROTECT, BROWNOUT
#use delay(clock=4000000)
unsigned char x, pin[4], rpm_digit1, rpm_digit2;
unsigned int rpm_2dig, time, time1, time2, tick;
unsigned long rpm;
float freq;
#define IN_F PIN_A4
#define D1_1 PIN_A0
#define D1_2 PIN_A1
#define D1_3 PIN_A2
#define D1_4 PIN_A3
#define D2_1 PIN_B1
#define D2_2 PIN_B2
#define D2_3 PIN_B4
#define D2_4 PIN_B5
#define STRB PIN_B0
void initialize(){
freq=0; rpm=0; rpm_digit1=0; rpm_digit2=0; x=0; rpm_2dig=0;
for (x=1;x<4;x++)
pin[x]=0;
}
long count_rpm(){
while( input(IN_F));
set_timer1(0);
time1=get_timer1();
enable_interrupts(GLOBAL);
while(!input(IN_F));
while(tick < 10){
if (input(IN_F)>0) tick++;
}
disable_interrupts(INT_TIMER1);
time2=get_timer1();
time=time2-time1;
freq=tick/time; //OK, this is not the correct expression, I have to calculate the right frequency.
rpm=25*freq;
return rpm;
}
void display(long rpm){
//This function indicates the 1000th and 100th digits of the taken value - translates to BCD.
//The correspondence between the freq and the rpm is: 1Hz=25RPM - in case of 4 cyls engine.
//Easy round-up method is to increment the value with 50 then cut off the last 2 digit.
rpm_2dig=(rpm+50)/100;
rpm_digit1=(rpm_2dig-rpm_2dig%10)/10;
output_low(STRB);
for(x = 0; x < 4; x++){
pin[x] = bit_test(rpm_digit1,x);
if (pin[0] > 0) output_high(D1_1);
else output_low(D1_1);
if (pin[1] > 0) output_high(D1_2);
else output_low(D1_2);
if (pin[2] > 0) output_high(D1_3);
else output_low(D1_3);
if (pin[3] > 0) output_high(D1_4);
else output_low(D1_4);
}
rpm_digit2=rpm_2dig-rpm_digit1*10;
for(x = 0; x < 4; x++){
pin[x] = bit_test(rpm_digit2,x);
if (pin[0]) output_high(D2_1);
else output_low(D2_1);
if (pin[1]) output_high(D2_2);
else output_low(D2_2);
if (pin[2]) output_high(D2_3);
else output_low(D2_3);
if (pin[3]) output_high(D2_4);
else output_low(D2_4);
}
output_high(STRB);
}
void main(){
initialize();
setup_timer_1(T1_INTERNAL | T1_DIV_BY_8);
enable_interrupts( GLOBAL );
enable_interrupts(INT_TIMER1);
while(1){
count_rpm();
//rpm=2485; //only for testing the display
display(rpm);
}
} |
Hope I told every important information belonging to this issue.
Thank you in advance,
_________________
Regards,
zipmmcs |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Tue Jun 10, 2008 4:52 pm |
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You enable the timer1 interrupt, but where is the handler?
And some minor issues: | Code: | for (x=1;x<4;x++)
pin[x]=0; |
Why not start with x=0? Now you are only initializing 3 of the 4 elements.
In count_rpm() you return variable rpm but you never use the returned value, instead you have declared rpm as a global variable and access the value directly. Stick to one method of programming, use global variables or return values but mixing both is confusing and wasting memory. Personally I don't like global variables as they go against the practice of encapsulation and make it impossible for the compiler to optimize RAM memory usage. |
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RArtz
Joined: 28 May 2008
Posts: 7
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| Posted: Wed Jun 11, 2008 10:09 am |
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ya, you need to do:
rpm = count_rpm();
display(rpm); |
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zipmmcs
Joined: 03 Feb 2008
Posts: 2
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| Posted: Mon Jun 16, 2008 12:07 pm |
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Thank you for the answers.
Finally me and one of my friend carried out a particular solution using the CCP module. When the code is finished, I will post the whole program.
_________________
Regards,
zipmmcs |
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