Frequency Counter with decimal

DigitalBob

Greetings All

Does anyone have a spin solution for a frequency counter that will read in decimal. Example 200.3 hertz or 1200.7 hertz, nothing high frequency maybe 10-20 KHz tops.
Thanks in advance

Bob

kwinn

Take a look at these objects. May not be exactly what you want but one of them should be a good starting point.

http://obex.parallax.com/object/118
http://obex.parallax.com/object/241
http://obex.parallax.com/object/478

Bean

Here is one I wrote in PropBasic (spin files are included, but they are PASM).

http://forums.parallax.com/showthread.php/123170

Bean

localroger

You're not going to be able to do that with raw counting because you'd have to accumulate for 10 seconds. You'll have to measure the period and divide into CLKFREQ. At 20 KHz one cycle is 4,000 80 MHz clocks, so to get 200,000 clocks (for 0.1 Hz accuracy) you would need to time the period of 500 cycles. At 1 KHz this will take half a second, so you'd probably want to sample a single cycle and then use that estimate to figure out how long a train to count for fine accuracy. I suspect measuring the period of a train of N pulses is something the counter-timers can do but I haven't worked with them enough to know how. I'd probably just do it in PASM by using WAITPEQ in a countdown loop. That way it would be extremely simple.

Alexander (Sandy) Hapgood

DigitalBob wrote: »

Greetings All

Does anyone have a spin solution for a frequency counter that will read in decimal. Example 200.3 hertz or 1200.7 hertz, nothing high frequency maybe 10-20 KHz tops.
Thanks in advance

Bob

I recently had a similar problem. I knew the wavelength in clock ticks but needed an accurate frequency to three decimal places for display purposes. Note the use of the modulas operator ( // ) in line 3.

clkfreq: 80_000_000 ticks
wavelength : 1_340_005 ticks
clkfreq / wavelength = 59.701

WaveLength := 1340005
WholeFreq := clkfreq / WaveLength                '59
FractionalFreq := clkfreq // WaveLength          '939_705
FractionalFreq := FractionalFreq * 1000          '939_705_000
FractionalFreq := FractionalFreq / WaveLength    '701

I then displayed the two variables ( WholeFreq and FractionalFreq ) seperated by a decimal point.

Sandy

DigitalBob

Problem Solved

I received some good tips but no cigar. I saw this post written by someone and tweeked it to give the desired output. It works good for my needs I'm only interested in the low end 400 hz , 1800 hz. etc.. I gets it a little sloppy above 2000 hz. You can tweek the math and waitcnt to give the desired output.

{ Frequency Counter






}


CON

_xinfreq = 5_000_000
_clkmode = xtal1 + pll16x


LCD_Pin = 1 'The LCD is connected to pin A0.
LCD_Baud = 19_200 'Baud
LCD_Lines = 2 'The number of lines on this LCD
In = %0
On = 1
Off = 0
G=0.1


CountPin = 5 'Input Pin for counter




Obj


LCD : "debug_lcd" 'Creates the object LCD from "debug_lcd"
F : "FloatMath"
FS : "FloatString"



Var

long Cog
long PNCount[2] '0 is posicount 1 is neg count
Long Frequency
long X1
long X2

Pub Main | TotCnt , freq




Cog := cognew(@entry, @PNCount[0] ) + 1











If LCD.init(LCD_Pin, LCD_Baud, LCD_Lines) 'Initialize the LCD object LCD.Cursor(Off) 'Set cursor off
LCD.Backlight(True) 'Set backlight on
LCD.Cls

Repeat


LCD.Gotoxy(0,0)
LCD.str(string("pos")) 'Positive Count
LCD.dec( PNCount[0] )
' LCD.out($0D)
LCD.Gotoxy(8,0)
LCD.str(string("neg="))
Lcd.dec( PNCount[1] )



TotCnt := (PnCount[0] *100) / (PnCount[0] + PnCount[1])

LCD.Gotoxy(8,1)
Lcd.str(string("Dec")) '% Positive
Lcd.str( x2 ) 'Displays float string



Freq := (12000 * 5556 ) / ( (PnCount[0] + PnCount[1]) ) 'Tweek the math for desire reading


X1:= F.FFloat(freq) ' Converts Freq to a float

X2:=(FS.FloatToString(F.FMul(x1,g))) 'Converts float to string

LCD.Gotoxy(0,1)
Lcd.str(string("frq="))
Lcd.dec( Freq )




waitcnt(clkfreq * 1 + cnt )

lcd.cls
LCD.Backlight(True) 'Set backlight on


PUB stop

if Cog
cogstop(Cog~ - 1)










DAT

org 0
entry

{
'

---

Debugger Kernel add this at Entry (Addr 0)

---

long $34FC1202,$6CE81201,$83C120B,$8BC0E0A,$E87C0E03,$8BC0E0A
long $EC7C0E05,$A0BC1207,$5C7C0003,$5C7C0003,$7FFC,$7FF8
'

---

}
'


muxz dira , PinMask ' Configure Pin as inputs (0) as Z is zero

mov addr , par 'par has address of first variable to write back which is PosCnt
add addr, #$4 'This is address of second variable to write back NegCnt

:MainLoop mov PosCnt ,#0 'set counters to zero
mov NegCnt ,#0 wc 'set counters to zero c set to zero
waitpne PinMask , PinMask 'waits for negative on input ina
waitpeq PinMask , PinMask 'waits for positive on input


:PosLoop Add PosCnt , #1 'adds 1 to positive count
Test PinMask , ina wz 'tests and sets z= 0 if both = 1
'if both are = 1 then result is 1 and z = 0

if_NZ jmp #:Posloop 'stays in loop as long as input is high z=0


:NegLoop Add NegCnt , #1 'adds 1 to positive count
Test PinMask , ina wz 'tests and sets z= 0 if both = 1
'if both are = 1 then result is 1 and z = 0

if_Z jmp #:Negloop 'stays in loop as long as input is low z=1

Wrlong PosCnt , par
Wrlong NegCnt , addr

jmp :MainLoop




' VARIABLES

PosCnt Long 0
NegCnt Long 0
PinMask long |< CountPin 'This creates a pin mask with a 1 and CountPin zeros to the right


PinState res 1
addr res 1 'register for sending data to main program

Phil Pilgrim (PhiPi)

DigitalBob,

Please see my note in your other post about how to post code in the forum.

Thanks,
-Phil