read a pwm

[fred.pacc]

hello,
I need to increase a frequency of 120Hz to 10kHz PWM so
I have a measure of a pwm dutycyle has 120hz and take its value to send in another PWM at 10kHz with a pic 18F2420

can you give me a procedure?

thank you

[Ioannis]

I can give you an idea to start. Use the Pulsin command to measure the width of High and Low pulses. Or use timer.Start an stop the timers on each edge of the 120Hz pulse and then find the frequency or period.

Ioannis

[Acetronics2]

Hello

I think Darrel already has published something ( of course nice !!! ;) ) about that ...

Alain

Here it is ...



'************************************************* ***************
'* Name : FREQx2.bas *
'* Author : Darrel Taylor *
'* Date : 3/2/2007 *
'* Version : 3.0 *
'* Notes : Doubles the frequency of input pulses, *
'* : and maintains the same DutyCycle as the Input. *
'* : Range = .1hz to 500 hz (0-40% max DutyCyle) *
'* : Target = PIC12F629/675 *
'************************************************* ***************
@ __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF
DEFINE NO_CLRWDT 1
Clear
SpeedPin VAR GPIO.2 ; Input from speed sensor
SpeedX2Pin VAR GPIO.4 ; Output to Speedometer
IdleState VAR GPIO.0 ; State of input when sensor
; is not on a "Slot"
Invert VAR GPIO.1 ; Inverts output if = 1
OPTION_REG.7 = 0 ; enable weak Pull-ups
WPU = 3 ; weak Pull-up on GP0 and GP1
;_________________________________________________ ____________________________
LastState VAR BIT ; Last state the Input changed to
LoopCount VAR byte ; Counts the loops of each pulse
LoopCount1 VAR byte
LoopCount2 VAR byte
PulseWidth VAR byte BANK0 ; Counts the loops of output pulse
PulseWidth1 VAR byte BANK0
PulseWidth2 VAR byte BANK0
LastPulseWidth VAR byte ; saved width of last pulse
LastPulseWidth1 VAR byte ; so it can duplicate it
LastPulseWidth2 VAR byte
CycleWidth VAR byte BANK0 ; Counts the loops of output cycle
CycleWidth1 VAR byte BANK0
CycleWidth2 VAR byte BANK0
OutPulseCount VAR BIT

CMCON = 7
'ANSEL = 0 ; for 12F675
SpeedX2Pin = IdleState
OUTPUT SpeedX2Pin
Main:
LoopCount = LoopCount + 1 ; 24-bit counter
If LoopCount = 0 Then
LoopCount1 = LoopCount1 + 1
if LoopCount1 = 0 then
LoopCount2 = LoopCount2 + 1
endif
endif
IF SpeedPin <> LastState then ; If Input State Changed?
LastState = SpeedPin

if LastState = (IdleState ^ 1) then ; Start of Input Pulse
CycleWidth = LoopCount
CycleWidth1 = LoopCount1
CycleWidth2 = LoopCount2
ASM
bcf STATUS,C ; CycleWidth = LoopCount / 2
rrf _CycleWidth2, F ; Output Cycle is half of Input
rrf _CycleWidth1, F
rrf _CycleWidth, F
ENDASM
LoopCount = 0 ; reset LoopCount
LoopCount1 = 0
LoopCount2 = 0
else ; End of Input Pulse
PulseWidth = LoopCount
PulseWidth1 = LoopCount1
PulseWidth2 = LoopCount2
ASM
bcf STATUS,C ; PulseWidth = PulseWidth / 2
rrf _PulseWidth2, F ; Output Pulse is half of Input
rrf _PulseWidth1, F
rrf _PulseWidth, F
ENDASM
LastPulseWidth = PulseWidth
LastPulseWidth1 = PulseWidth1
LastPulseWidth2 = PulseWidth2
SpeedX2Pin = ((IdleState ^ 1) ^ Invert) ; start First Output Pulse
OutPulseCount = 0
endif
else
if SpeedX2Pin = ((IdleState ^ 1) ^ Invert) then
if PulseWidth = 0 then ; countdown output time (24bit)
if PulseWidth1 = 0 then
if PulseWidth2 = 0 then
SpeedX2Pin = (IdleState ^ Invert) ; end of pulse,
else ; wait for next transition
PulseWidth2 = PulseWidth2 - 1
PulseWidth1 = 255
PulseWidth = 255
endif
else
PulseWidth1 = PulseWidth1 - 1
PulseWidth = 255
endif
else
PulseWidth = PulseWidth - 1
endif
else
@ NOP ; Keep the loop symmetrical
@ NOP
@ NOP
@ NOP
@ NOP
@ NOP
endif

if OutPulseCount = 0 then
if CycleWidth = 0 then ; countdown to Midpoint of cycle
if CycleWidth1 = 0 then
if CycleWidth2 = 0 then
SpeedX2Pin = ((IdleState ^ 1) ^ Invert) ; Start second pulse
OutPulseCount = 1
PulseWidth = LastPulseWidth
PulseWidth1 = LastPulseWidth1
PulseWidth2 = LastPulseWidth2
else
CycleWidth2 = CycleWidth2 - 1
CycleWidth1 = 255
CycleWidth = 255
endif
else
CycleWidth1 = CycleWidth1 - 1
CycleWidth = 255
endif
else
CycleWidth = CycleWidth - 1
endif
else
@ NOP ; Keep the loop symmetrical
@ NOP
@ NOP
@ NOP
@ NOP
endif
endif
goto Main
end


...

Just for the idea ... !