Interfacing MH-Z16 CO2 sensor with PBP?

[HenrikOlsson]

More than one issue with that piece of code. For one, you're running at 64MHz so it's probably going to wrap around X variable quite quickly giving you weird results. I'd try something like this:

Th VAR WORD
Tl VAR WORD

PWIN VAR PORTB.0


Main:
    GOSUB Measure
    LCDOUT $FE, $01, "High: ",  DEC Th
    LCDOUT $FE, $C0, "Low: ",   DEC Tl
GOTO Main

Measure:
  Th = 0
  Tl = 0

  WHILE !PWIN : WEND	' Wait for rising edge

  WHILE PWIN			' Measure high pulse width
    Th = Th + 1
    PAUSEUS 999
  WEND

  WHILE !PWIN			' Measure low pulse width
    Tl = Tl + 1
    PAUSEUS 999
  WEND

RETURN

Once you have that working, displaying pulsewidth values matching what you see on the scope you can A) increase resolution (if needed) and/or B) calculate PPMs or percentage or whatever you want to display. Small steps...