Pulse Capture 50% duty, varying Freq

Rabbit
1

Hi All

I have built a data logger type of “Black Box” to be installed on a boat.

I’m using a BL4S200 in a waterproof housing,

We want to record wind speed and I have modified a standard wind instrument so that I can get a raw signal from the anomemeter. This signal is a square wave, 2 pulses per revolution. It is 50 % duty cycle pulse, with the frequency increasing with wind speed. So low wind speeds the frequency on only a few Hz, and a few hundred Hz at high wind speeds.

I have tried getBegin() and getEnd() functions, using DIO1, but not having much success.

I looked at the sample IC_Test.C but could not figure out how to access PC5 as on the BL4S200 this port/bit seems to go to the RIO chip.

The following code is what I created to test capturing a 50% duty square wave from DIO1 (taken from the sample file pulse_capture.c as found in the BlxS200/DIO directory

I’m not a great programmer, more of a technican. But struggling through Dynamic C.

Any advise appreciated

/******************************************

	This sample program was created from  code within

   samples/blxs200/DIO/pulse_capture.c

*********************************************/

#class auto
#use "BLxS2xx.lib"
#define USE_PRESCALE BL_PRESCALE

// set the STDIO cursor location and display a string
void DispStr(int x, int y, char *s)
{
   x += 0x20;
   y += 0x20;
   printf ("\x1B=%c%c%s", x, y, s);
}

void main()
{
   int i;
   word begin;
   word end;
   char pulse_width[80];

   // Initialize the controller
	brdInit();

 // Setup input capture for begin=rise & end=fall on the same channel
 setCapture(1, BL_CNT_RUN, BL_EVENT_RISE,
	                 BL_SAME_CHANNEL | BL_EVENT_FALL | USE_PRESCALE);
   i = 0;
	while (i < 10000)
	{
   		resetCounter(1);
	      getBegin(1, &(begin));
	      getEnd(1, &(end));

      // Display current captured begin and end values from pulses
      sprintf(pulse_width,"%d, 	 Ch. 0 Begin = %u, End = %u,  Diff = %u 
",
      		i,
                 begin,
                 end,
      		(begin - end)
                 );

     DispStr(1,2,(pulse_width));
     i = i+1;
	}
}
2

Also

I was having trouble finding any referance to the functions

setCounter()
GetBegin()
getEnd()
resetCounter() etc …

in the Dynamic C 4000, 5000, 6000, reference manual.

3

You will find the documentation for these functions in the BL4S200 user manual as they are in board specific libraries.

Regards,
Peter

4

Ahhhh …

I thought I had downloaded that manual but, revisiting the DIGI web site, I have now found a manual with descriptions of those functions.

Thanks for the direction Peter

Simon

5

OK, So I have spent some time with the correct manual,

But am still having some difficulty.

I can use the setCounter() function effectively, and as I increase frequency of my 50% duty cycle square wave from about 80hz to 10 K hz I see the counter increase in speed.

But If trying setCapture() to read the width of a single pulse I seem to just get some noise.

Attached here are the very simple bits of code I’m using to test this.

6

Here is the code I’m using to test the hardware, and the fact that I’m actually reading in the pulses to DIO1

This works fine and I see the counter output speed increase as I increase the speed (frequency from about 80 hz to 10K hz).


 #class auto 
#use "BLxS2xx.lib"  

void main()
 {     
word wind;  	

brdInit();    
setCounter(1, BL_UP_COUNT, BL_EDGE_RISE, BL_EDGE_RISE);

  	while (1) 	{ 			

      getCounter (1, &(wind));         	
       printf("%u 
", wind );  	
       } 
}
7

However when I try to read the length of a single pulse using setCapture() I just seem to get noise.

The Begin and End numbers are within 1, regardless of my change in input frequency of my 50% duty cycle square wave (5vdc P)

Is there some issue with using PRESCALE or RIO_FREQ that I’m not understanding ?


#class auto
#use "BLxS2xx.lib"

void main()
{

   word begin;
   word end;
   word wind;
   char pulse_width[80];

   // Initialize the controller
	brdInit();

 // Setup input capture for begin=rise & end=fall on the same channel
 setCapture(1, BL_CNT_BEGIN_END, BL_EVENT_RISE, BL_SAME_CHANNEL | BL_EVENT_FALL|  BL_PRESCALE );

	while (1)
	{
              resetCounter(1);
	      getBegin(1, &(begin));
	      getEnd(1, &(end));
	      getCounter (1, &(wind));
         
      sprintf(pulse_width,"Ch. 1 Begin = %u, End = %u,  Diff = %u  Wind = %u 
",
                  begin,
                  end,
                  (end - begin),
                  wind
                  );

     printf(pulse_width);

	}
}