Need advice for creating nS time delay

[Ingvar]

My guess is that this code will work......

@ device  pic12F675, protect_off, mclr_off

define OSC 4
DEFINE OSCCAL_1K 1	            'Set OSCCAL for 1K device

DataPin     VAR GPIO.0              'DOCI on the PIR
PIRdata     VAR WORD                
i           VAR BYTE

ANSEL = 0                           'No AD on 12F675
CMCON = %00010111                   'Digital pins - no comparator
WPU = 0                             'No pullups

WHILE 1                             'Do forever
    HIGH GPIO.1                     'Set a pin to time the reading
    GOSUB ReadPIR                   'Call the Sub
    LOW GPIO.1                      'Reset a pin to time the reading
    PAUSE 10                        'Just something to sync the scope
WEND
   

ReadPIR:
    INPUT DataPin                   'Let PIR control the Datapin
    PIRdata = 0                     'Use this time to let Datapin settle
    WHILE DataPin = 0 : WEND        'Wait for PIR to indicate "new data"
    PAUSEUS 25                      'Wait for PIR to fiddle with the data
    FOR i = 14 to 0 STEP -1         'Loop to get 15bits
        LOW DataPin                 'Force Datapin Low
        HIGH Datapin                'Force Datapin High
        INPUT Datapin               'Let PIR control the Datapin
' You may need a short pause here if you have long wires to the PIR    
        PIRdata.0(i) = Datapin      'Sample the datapin
    NEXT
    LOW DataPin                     'Force Datapin Low
    INPUT Datapin                   'Let PIR control the Datapin
    RETURN
    
END

... it compiles and runs as expected. Only problem is that i don't have a PIR to verify it with, it does however look OK on a scope. If i have interpreted the datasheet correctly you should be flying.

/Ingvar

[sayzer]

Ingvar,

I tested your code a minute ago; with some additions;

Congratulations! It works flawlessly.

My code is almost the same as yours.

What I see here is that, when we set the pin HIGH and then LOW, the time it takes to set the pins is already good enough for the sensor reading.

[Ingvar]

Good to know that we have working code ... if i ever buy one of theese PIRs.