Copyright © Parallax Inc. PING))) Ultrasonic Distance Sensor (#28015) v2.0 2/4/2013 Page 8 of 9
Propeller Microcontroller
{{
***************************************
* Ping))) Object V1.1 *
* (C) 2006 Parallax, Inc. *
* Author: Chris Savage & Jeff Martin *
* Started: 05-08-2006 *
***************************************
Interface to Ping))) sensor and measure its ultrasonic travel time. Measurements can be in
units of time or distance. Each method requires one parameter, Pin, that is the I/O pin that
is connected to the Ping)))'s signal line.
┌───────────────────┐
│┌───┐ ┌───┐│ Connection To Propeller
││ ‣ │ PING))) │ ‣ ││ Remember PING))) Requires
│└───┘ └───┘│ +5V Power Supply
│ GND +5V SIG │
└─────┬───┬───┬─────┘
│ │ 1K
└┘ └ Pin
--------------------------REVISION HISTORY--------------------------
v1.1 - Updated 03/20/2007 to change SIG resistor from 10K to 1K
}}
CON
TO_IN = 73_746 ' Inches
TO_CM = 29_034 ' Centimeters
PUB Ticks(Pin) : Microseconds | cnt1, cnt2
''Return Ping)))'s one-way ultrasonic travel time in microseconds
outa[Pin]~ ' Clear I/O Pin
dira[Pin]~~ ' Make Pin Output
outa[Pin]~~ ' Set I/O Pin
outa[Pin]~ ' Clear I/O Pin (> 2 μs pulse)
dira[Pin]~ ' Make I/O Pin Input
waitpne(0, |< Pin, 0) ' Wait For Pin To Go HIGH
cnt1 := cnt ' Store Current Counter Value
waitpeq(0, |< Pin, 0) ' Wait For Pin To Go LOW
cnt2 := cnt ' Store New Counter Value
Microseconds := (||(cnt1 - cnt2) / (clkfreq / 1_000_000)) >> 1 ' Return Time in μs
PUB Inches(Pin) : Distance
''Measure object distance in inches
Distance := Ticks(Pin) * 1_000 / TO_IN ' Distance In Inches
PUB Centimeters(Pin) : Distance
''Measure object distance in centimeters
Distance := Millimeters(Pin) / 10 ' Distance In Centimeters
PUB Millimeters(Pin) : Distance
''Measure object distance in millimeters
Distance := Ticks(Pin) * 10_000 / TO_CM ' Distance In Millimeters
