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Calculation of pulse rate

 
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Guest
Calculation of pulse rate
PostPosted: Tue Jan 19, 2010 11:18 pm     Reply with quote
Code:
for (x=5;x<128;x++)
{
      read1 = read_adc();
      newresult1 = (float)read1;
   if ( newresult1 > max_adc1 )
   {
      max_adc1 = newresult1;
      time1=x   ;

      for (time1;x<128;x++)
         {
               read2 = read_adc();
               newresult2= (float)read2;
         if ( newresult2 > max_adc2 )
            {
               max_adc2 = newresult2;
               time2=x   ;
            }
         else
            total_time = time2 - time1;
            pulse_rate = 60 / total_time;
         }
   }
}

sprintf(String_Buff,pulse_rate);
LCD_Print_String(YELLOW, BLACK, 75, 75,String_Buff);   



Hi, basically I want to calculate the pulse rate between 2 waveform and X is my time domain (between 5 to 128).

Why is it that when I display the value out onto my LCD (nokia6610) , they are in a funny code?
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue Jan 19, 2010 11:33 pm     Reply with quote
Quote:
sprintf(String_Buff, pulse_rate);

You don't have a format string in your sprintf() statement.
Guest
PostPosted: Wed Jan 20, 2010 12:11 am     Reply with quote
Code:
          sprintf(String_Buff, "%d", pulse_rate);


ok thanks alot of on that. but why is it that my value is wrong, is there any errors in my code? i want to get the peaks of every waveform to calculate the pulse rate
Ttelmah
Guest
PostPosted: Wed Jan 20, 2010 4:25 am     Reply with quote
We can't tell.
The problem is that the results at every stage, depend on what values are in variables when you arrive at the code, and on the types of the variables. You show neither....
There are some comments.
Start with 'read1'. This needs to be an int16 or larger, assuming that you have the ADC set to return a 10 bit value. If not, it can bean 8bit integer.
Then you convert the value to a float (the cast is not needed, conversion is automatic when you pass a variable to a larger type).
You then waste a _lot_ of time. It'd be much better for maxadc1, to be an integer of the same type as read1, and to perform the comparison on integers, rather than float values.
Then the question is what you are actually trying to measure.
If you are looking for a 'peak', then your detection needs to be something like:
Code:

   int16 maxadc1=0;
   int16 maxadc2=0;
   int16 temp;
   int x, time1, time2;

   for (x=5;x<128;x++) {
      temp = read_adc();
      if ( temp < max_adc1 ) {
          //If the signal starts to _fall_,the highest point
          //was the last reading
          time1=x-1;
          for (;x<128;x++) {
            temp = read_adc();
            if (temp < max_adc2 ) {
                time2=x-1; //again the 'peak', is one count before the signal
                //falls.
                break;
                }
            else
                //Signal is rising
                maxadc2=temp;
          }
       }
       else
          //signal is rising
          maxadc1=temp;
   }
   total_time = time2 - time1;
   pulse_rate = 60 / total_time;

As you currently work, if the signal is rising, it'll be detected immediately, and drop straight through both tests....

Best Wishes
Guest
PostPosted: Thu Jan 21, 2010 9:38 am     Reply with quote
Ok, thanks for your reply. Somebody suggested to me using a timer to measure the time between the peak intervals instead of using the X - axis. The X axis are actually pixels on my LCD screen.

Code:

setup_timer_0(RTCC_INTERNAL|RTCC_DIV_128);
set_timer0(0) ; //this sets timer0 register to 0

   int16 maxadc1=0;
   int16 maxadc2=0;
   int16 temp,time1, time2,total_time, pulse_rate;
   unsigned int x, axis1;

for (x=5;x<128;x++)
{
      temp = read_adc();
   if ( temp > max_adc1 ) // if the new result is higher than the current max adc value, it will overwrite the new result as the max adc. if the new result is smaller, it will go on the find the next peak

   {
      max_adc1 = temp; // overwrite the new result as the new max adc.
   }
   else
                axis1 = x;
      time1=get_timer0(); //this will read the timer0 register value, the time of the 1st peak value.

      for (axis1;x<128;x++) // repeating the same process the get the next peak, after the 1st peak .
         {
               temp = read_adc();
         if ( temp > max_adc2 ) // same as above
            {
               max_adc2 = temp;
            }
         else
            time2=get_timer0(); //this will read the timer0 register value , the time of the 2nd peak value.
            total_time = time2 - time1;
            pulse_rate = 60 / total_time;


Am i correct with my code? if i am wrong, please guide me. Thanks in advance
Guest
PostPosted: Sat Jan 23, 2010 12:11 am     Reply with quote
Can anybody help me with this, why am I unable to get the 2nd timer0 value? I tested it out by setting it to 100, but when I display it on my screen, it states -80.
Code:

for (x=5;x<128;x++)
    {
     temp = read_adc();
     while(max_adc1<(float)temp)
       {
        max_adc1 = temp; // overwrite the new result as the new max adc.
       }

     set_timer0(50);
     axis1 = x;
     time1=get_timer0(); //this will read the timer0 register value, the time of the 1st peak value.
    }

for (axis1;x<128;x++) // repeating the same process the get the next peak, after the 1st peak .
    {
     temp = read_adc();

     while(max_adc2<(float)temp)
       {
        max_adc2 = temp;
       }

    set_timer0(100);
    time2=get_timer0(); //this will read the timer0 register value , the time of the 2nd peak value.
    total_time = time2 - time1;
    pulse_rate = 6000 / total_time;
   }
}
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