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turbotom93
Joined: 24 Apr 2009
Posts: 1
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| int32 division will not display in terminal via RS232 |
 Posted: Fri Apr 24, 2009 12:45 am |
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Good morning,
I am working on a project that uses two light sensors (one inside and one outside) to determine how much an electrochromic window has tinted. I am trying accomplish this by comparing the ratio of the two sensors which are read into the ADC. Right now I am just trying to read the ratio of the two sensors. Eventually I will set of IF statements to see if the window is 0%,25%,50%,75%, or 100% tinted (the one for 0% is set up already). I can get values for the sensors, but when I try to read the ratio from the RS232 I get 0.
I am using a PIC16F887 and version 4.020B of the compiler.
| Code: | #if defined(__PCM__)
#include <16F887.h>
#device ADC=10
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
long read_adc_average1()
{
long value;
int i;
//set_adc_channel(A/D_Input);
set_adc_channel(2);
delay_ms(150);
value=0;
for ( i=0 ; i<8 ; i++ ) {
value += Read_ADC();
delay_ms(10);
}
/* divide by 8 */
value = value / 8;
return value;
}
long read_adc_average2()
{
long value;
int i;
//set_adc_channel(A/D_Input);
set_adc_channel(3);
delay_ms(150);
value=0;
for ( i=0 ; i<8 ; i++ ) {
value += Read_ADC();
delay_ms(10);
}
/* divide by 8 */
value = value / 8;
return value;
}
void main()
{
int8 scaleratio;
int16 VoltsScaleFactor;
int32 ScaledReading1;
int32 ScaledReading2;
int32 ratio;
VoltsScaleFactor=4790;
setup_adc_ports(ALL_ANALOG);
setup_adc(ADC_CLOCK_INTERNAL);
while(1)
{
//Here we read the A/D converter, and display the appropriate reading on the LCD.
ScaledReading1=((int32)read_adc_average1()*VoltsScaleFactor)/1000;
ScaledReading2=((int32)read_adc_average2()*VoltsScaleFactor)/1000;
ratio=(ScaledReading1/ScaledReading2);
if (ratio==1){
printf("0 tint\n\r");
}//endif
else{
ratio *=100000;
printf("ratio: %04.3w\n\r",ratio);
// scaleratio = (int8)(ratio);
// Here we send the reading to the serial port
printf("Inside_Sensor: %04.3w\n\rOutside_Sensor: %04.3w\n\r", ScaledReading1,ScaledReading2);
delay_ms(250);
}//endelse
}//endwhile
} |
output in terminal:
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Apr 24, 2009 12:51 am |
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Do a test program. Get rid of 90% of your code, and make a little test
program that emulates what you're doing, except that it loads 'ratio' with
some fixed value, and test if it works. This will help you to concentrate
on the problem and find out exactly what's wrong. |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Integer divsion displays correctly! |
| Posted: Fri Apr 24, 2009 1:16 am |
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You have ScaledReading1 < ScaledReading2, so the integer quotient ScaledReading1/ScaledReading2 should be supposed to be zero. Try with a calculator!
To get a correct 4.3 fixedpoint result, calculate 1000*ScaledReading1/ScaledReading2 instead. |
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