Calculating Pulse per minute in a FPGA

C

Cory Shol

Guest
Hi all,

Another problem from the two year FPGA newbie.


I am working on a new work project that does all this magnificent things and now I am a little stumped on a rather easy to understand problem.

I need to calculate how many pulses per minute of an input to display out of a Seven segment display.

I have completed all the user interface stuff and it works fine etc...

The problem is with the calculation.

I am running at 25 Mhz clock. 40 ns period.

Basically I wait for a rising edge of the first pulse and reset my counter. Every rising edge of my 25 Mhz clock I increment the counter until the next rising edge of the pulse.

Basically the Pulse can be as slow as 15 ppm to 1000 ppm. So if you have a 1000 ppm pulse inputting you would see 1500000 25 Mhz clock counts.

The hard part is converting 1500000 counts into a PPM.

I know the math is easy : 60 /[(count)*(Period of Clk)] = PPM

60/ (1500000 *(0.00000004))= 1000 ppm

Doing division in VHDL seems to be tough.

I have one algorithm idea of doing basically the basic of all basics.

which is: 60/clkPeriod = 1.5 billion
initially do this:

newCount <= newCount - count;
quotient <= quotient + 1;

Then after initial do this:

if(newCount >= Count) then
newCount <= newcount -count;
quotient <= quotient + 1;
else
finalanswer <= quotient;
end if;


Are there any other easy algorithms that are relatively easy to implement? Or a standard way the VHDL community does divisions?

Thanks

Cory
 
On Tue, 28 May 2013 10:01:02 -0700 (PDT)
Cory Shol <cory.shol@gmail.com> wrote:

Hi all,

Another problem from the two year FPGA newbie.


I am working on a new work project that does all this magnificent things and now I am a little stumped on a rather easy to understand problem.

I need to calculate how many pulses per minute of an input to display out of a Seven segment display.

I have completed all the user interface stuff and it works fine etc...

The problem is with the calculation.

I am running at 25 Mhz clock. 40 ns period.

Basically I wait for a rising edge of the first pulse and reset my counter. Every rising edge of my 25 Mhz clock I increment the counter until the next rising edge of the pulse.

Basically the Pulse can be as slow as 15 ppm to 1000 ppm. So if you have a 1000 ppm pulse inputting you would see 1500000 25 Mhz clock counts.

The hard part is converting 1500000 counts into a PPM.

I know the math is easy : 60 /[(count)*(Period of Clk)] = PPM

60/ (1500000 *(0.00000004))= 1000 ppm

Doing division in VHDL seems to be tough.

I have one algorithm idea of doing basically the basic of all basics.

which is: 60/clkPeriod = 1.5 billion
initially do this:

newCount <= newCount - count;
quotient <= quotient + 1;

Then after initial do this:

if(newCount >= Count) then
newCount <= newcount -count;
quotient <= quotient + 1;
else
finalanswer <= quotient;
end if;


Are there any other easy algorithms that are relatively easy to implement? Or a standard way the VHDL community does divisions?

Thanks

Cory
Click to expand...
Stupid question: if you're trying to count how many pulses per minute
you get, why don't you just block off 1 minute chunks of time, and see
how many pulses you get in each chunk?

--
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order. See above to fix.
 
On Tuesday, May 28, 2013 12:19:31 PM UTC-5, Rob Gaddi wrote:
On Tue, 28 May 2013 10:01:02 -0700 (PDT)

Cory Shol <cory.shol@gmail.com> wrote:



Hi all,



Another problem from the two year FPGA newbie.





I am working on a new work project that does all this magnificent things and now I am a little stumped on a rather easy to understand problem.



I need to calculate how many pulses per minute of an input to display out of a Seven segment display.



I have completed all the user interface stuff and it works fine etc...



The problem is with the calculation.



I am running at 25 Mhz clock. 40 ns period.



Basically I wait for a rising edge of the first pulse and reset my counter. Every rising edge of my 25 Mhz clock I increment the counter until the next rising edge of the pulse.



Basically the Pulse can be as slow as 15 ppm to 1000 ppm. So if you have a 1000 ppm pulse inputting you would see 1500000 25 Mhz clock counts.



The hard part is converting 1500000 counts into a PPM.



I know the math is easy : 60 /[(count)*(Period of Clk)] = PPM



60/ (1500000 *(0.00000004))= 1000 ppm



Doing division in VHDL seems to be tough.



I have one algorithm idea of doing basically the basic of all basics.



which is: 60/clkPeriod = 1.5 billion

initially do this:



newCount <= newCount - count;

quotient <= quotient + 1;



Then after initial do this:



if(newCount >= Count) then

newCount <= newcount -count;

quotient <= quotient + 1;

else

finalanswer <= quotient;

end if;





Are there any other easy algorithms that are relatively easy to implement? Or a standard way the VHDL community does divisions?



Thanks



Cory







Stupid question: if you're trying to count how many pulses per minute

you get, why don't you just block off 1 minute chunks of time, and see

how many pulses you get in each chunk?



--

Rob Gaddi, Highland Technology -- www.highlandtechnology.com

Email address domain is currently out of order. See above to fix.
Click to expand...
Because The input of the pulse can change at any time. So if it changed within the minute period you wouldn't have the correct PPM.
 
On Tuesday, May 28, 2013 1:34:58 PM UTC-5, Cory Shol wrote:
On Tuesday, May 28, 2013 12:19:31 PM UTC-5, Rob Gaddi wrote:

On Tue, 28 May 2013 10:01:02 -0700 (PDT)



Cory Shol <cory.shol@gmail.com> wrote:







Hi all,







Another problem from the two year FPGA newbie.











I am working on a new work project that does all this magnificent things and now I am a little stumped on a rather easy to understand problem.







I need to calculate how many pulses per minute of an input to display out of a Seven segment display.







I have completed all the user interface stuff and it works fine etc...







The problem is with the calculation.







I am running at 25 Mhz clock. 40 ns period.







Basically I wait for a rising edge of the first pulse and reset my counter. Every rising edge of my 25 Mhz clock I increment the counter until the next rising edge of the pulse.







Basically the Pulse can be as slow as 15 ppm to 1000 ppm. So if you have a 1000 ppm pulse inputting you would see 1500000 25 Mhz clock counts.







The hard part is converting 1500000 counts into a PPM.







I know the math is easy : 60 /[(count)*(Period of Clk)] = PPM







60/ (1500000 *(0.00000004))= 1000 ppm







Doing division in VHDL seems to be tough.







I have one algorithm idea of doing basically the basic of all basics.







which is: 60/clkPeriod = 1.5 billion



initially do this:







newCount <= newCount - count;



quotient <= quotient + 1;







Then after initial do this:







if(newCount >= Count) then



newCount <= newcount -count;



quotient <= quotient + 1;



else



finalanswer <= quotient;



end if;











Are there any other easy algorithms that are relatively easy to implement? Or a standard way the VHDL community does divisions?







Thanks







Cory















Stupid question: if you're trying to count how many pulses per minute



you get, why don't you just block off 1 minute chunks of time, and see



how many pulses you get in each chunk?







--



Rob Gaddi, Highland Technology -- www.highlandtechnology.com



Email address domain is currently out of order. See above to fix.



Because The input of the pulse can change at any time. So if it changed within the minute period you wouldn't have the correct PPM.
Click to expand...
Also it is a requirement to update after every pulse.
 
On 5/28/2013 1:01 PM, Cory Shol wrote:
Hi all,

Another problem from the two year FPGA newbie.


I am working on a new work project that does all this magnificent things and now I am a little stumped on a rather easy to understand problem.

I need to calculate how many pulses per minute of an input to display out of a Seven segment display.

I have completed all the user interface stuff and it works fine etc...

The problem is with the calculation.

I am running at 25 Mhz clock. 40 ns period.

Basically I wait for a rising edge of the first pulse and reset my counter. Every rising edge of my 25 Mhz clock I increment the counter until the next rising edge of the pulse.

Basically the Pulse can be as slow as 15 ppm to 1000 ppm. So if you have a 1000 ppm pulse inputting you would see 1500000 25 Mhz clock counts.

The hard part is converting 1500000 counts into a PPM.

I know the math is easy : 60 /[(count)*(Period of Clk)] = PPM

60/ (1500000 *(0.00000004))= 1000 ppm

Doing division in VHDL seems to be tough.

I have one algorithm idea of doing basically the basic of all basics.

which is: 60/clkPeriod = 1.5 billion
initially do this:

newCount<= newCount - count;
quotient<= quotient + 1;

Then after initial do this:

if(newCount>= Count) then
newCount<= newcount -count;
quotient<= quotient + 1;
else
finalanswer<= quotient;
end if;


Are there any other easy algorithms that are relatively easy to implement? Or a standard way the VHDL community does divisions?
Click to expand...
Can you say, "look up table"?

--

Rick
 
On 5/28/2013 1:01 PM, Cory Shol wrote:
Hi all,

Another problem from the two year FPGA newbie.


I am working on a new work project that does all this magnificent things and now I am a little stumped on a rather easy to understand problem.

I need to calculate how many pulses per minute of an input to display out of a Seven segment display.

I have completed all the user interface stuff and it works fine etc...

The problem is with the calculation.

I am running at 25 Mhz clock. 40 ns period.

Basically I wait for a rising edge of the first pulse and reset my counter. Every rising edge of my 25 Mhz clock I increment the counter until the next rising edge of the pulse.

Basically the Pulse can be as slow as 15 ppm to 1000 ppm. So if you have a 1000 ppm pulse inputting you would see 1500000 25 Mhz clock counts.

The hard part is converting 1500000 counts into a PPM.

I know the math is easy : 60 /[(count)*(Period of Clk)] = PPM

60/ (1500000 *(0.00000004))= 1000 ppm

Doing division in VHDL seems to be tough.

I have one algorithm idea of doing basically the basic of all basics.

which is: 60/clkPeriod = 1.5 billion
initially do this:

newCount <= newCount - count;
quotient <= quotient + 1;

Then after initial do this:

if(newCount >= Count) then
newCount <= newcount -count;
quotient <= quotient + 1;
else
finalanswer <= quotient;
end if;


Are there any other easy algorithms that are relatively easy to implement? Or a standard way the VHDL community does divisions?

Thanks

Cory


Even updating 1000 times per minute you have a long time to make the
Click to expand...
calculation. If 1000 ppm is the highest rate, you could even do a
simple successive subtraction loop in 1000 cycles or about 40
microseconds with a 25 MHz clock.

On the other hand unless you're really short of resources, why not
just use a division IP core? I know Xilinx has it in Coregen, and
would assume other vendors offer one, too.

--
Gabor
 
On 5/28/2013 2:36 PM, Cory Shol wrote:
On Tuesday, May 28, 2013 1:34:58 PM UTC-5, Cory Shol wrote:
snip
On Tuesday, May 28, 2013 12:19:31 PM UTC-5, Rob Gaddi wrote:
Stupid question: if you're trying to count how many pulses per minute
you get, why don't you just block off 1 minute chunks of time, and see
how many pulses you get in each chunk?

On Tue, 28 May 2013 10:01:02 -0700 (PDT)
Cory Shol <cory.shol@gmail.com> wrote:

Because The input of the pulse can change at any time. So if it changed within the minute period you wouldn't have the correct PPM.

Also it is a requirement to update after every pulse.
Click to expand...
If you're display is seven segment then I have to assume it's for people
to read. A display that changes at 1KHz (your specified maximum rate)
would be very difficult for most people to make sense of. One solution
would be to average the PPM values that you collect over some period
that's closer to human perception scale and display that. Rob's
suggestion of simply accumulating pulses for one minute is a very simple
direct way to achieve that. Or you could accumulate pulses for one
second and display that value multiplied by 60. You'd have to how to
handle the 15 to 60 PPM range, but still the problem would be much easier.

As usual starting out with a good specification of what's really needed
makes developing a solution more efficient.
 
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