Motion detection with Ping

lardom

I'm working on a 'just for fun' autonomous mobile robot project and needed a way to know when movement started and stopped so I could start another 180° scan. I hope I'm not the only one who finds this code useful. Please tell me what you think.

'Larry McGrew, author  4/10/13
'The led should stay on as long as there is movement in front of the sensor
OBJ
    echo : "Ping"
   
PUB Activity_Test | j, A, B

  dira[17]~~                           'LED
  repeat 8             'stabilize ping
    B := echo.Inches(27)
    waitcnt(clkfreq/10+cnt)
  repeat                                      'motion starts
    A := B := echo.Inches(27)    
    repeat until A <> B
      B := echo.Inches(27)
      waitcnt(clkfreq/10+cnt) 
    outa[17]~~                          'LED


    repeat j from 1 to 6
      A := echo.Millimeters(27)       ' Millimeters   Centimeters
      waitcnt(clkfreq/40+cnt)
      B := echo.Millimeters(27)
      waitcnt(clkfreq/40+cnt)
      if A <> B
        j := j-1 
    outa[17]~                               'motion stops

davejames

...I'm guessing this is done in Spin?

lardom

Yes, it's Spin. Thanks for bringing this up. There was an error in the code that I missed when I posted it. The highlighted expression is the correction.

OBJ
    echo : "Ping"
   
PUB Activity_Test | j, A, B

  dira[17]~~                           'LED
  repeat 8             'stabilize ping
    B := echo.Inches(27)
    waitcnt(clkfreq/10+cnt)
  repeat                                      'motion starts
    A := B := echo.Inches(27)    
    repeat until A <> B
      B := echo.Inches(27)
      waitcnt(clkfreq/10+cnt) 
    outa[17]~~                          'LED


    repeat j from 1 to 6
      A := echo.Millimeters(27)       ' Millimeters   Centimeters
      waitcnt(clkfreq/40+cnt)
      B := echo.Millimeters(27)
      waitcnt(clkfreq/40+cnt)
      if A <> B
        [COLOR="#FF0000"]j := 1[/COLOR] 
    outa[17]~                               'motion stops