Sharp pulse on ADC input and NAP

[Bruce]

I have not tested this since I don't have a 12F675, but something like this should work. You might need to tweak the internal CVref settings.

Hook your sensor output to GPIO.1 Vin-. When your sensor outputs 1V (or anything > CVref) it should wake-up from sleep.

If you don't have PBP3 just get rid of the config line, and use what you have.

#CONFIG
  __config  _INTRC_OSC_NOCLKOUT & _BODEN_OFF & _MCLRE_OFF & _WDT_OFF & _CP_OFF
#ENDCONFIG
 
DEFINE OSCCAL_1K 1 ' load internal osc calibration value
 
LED VAR GPIO.2      ' LED output
CmpFlag VAR PIR1.3  ' alias comparator interrupt flag bit
CoutBit VAR CMCON.6 ' CMCON.6 is set while voltage on Vin- > CVref
 
ANSEL = 0          ' disable A/D
GPIO = 0           ' LED off on POR
TRISIO = %00000010 ' GPIO.1 = input for Vin- comparator, rest outputs
VRCON = %10100111  ' internal CVref enabled, low range.
                   ' CVref = (VR3:VR0 / 24) * VDD.
                   ' with (VR3:VR0) = 7 we have (7/24) * 3.3V
                   ' so internal CVref = 0.9625V
                   ' a voltage > 0.962V on Vin- (GPIO.1) will set COUT,
                   ' set the comparator interrupt flag, and wake us up.
CMCON = %00010100  ' Comparator w/o Output and with Internal Reference
 
PIR1 = 0           ' clear flags before enabling comparator int
PIE1 = %00001000   ' comparator interrupt enabled.
INTCON = %01000000 ' enable peripheral interrupts for comparator
                   ' global interrupts disabled, so there's no jump to
                   ' an interrupt vector. We're just waking-up from sleep.
 
TEST:
  WHILE CoutBit    ' wait for COUT to clear. This clears when the voltage on
  WEND             ' Vin- falls below the internal CVref
  CmpFlag = 0      ' clear comparator interrupt flag bit before entering sleep
  @ SLEEP          ' should sleep until comparator trips
  HIGH LED
  PAUSE 500
  LOW LED
  GOTO TEST
  end