'*********************************************************************************************
' Sonar-ranger.bas
' Program to control the Devantech SRF04 ultrasonic module. Measure 
' the distance between the the unit and an object. Convert the raw 
' data to inches and centimeters and then send the results to an LCD
' display. PicBasic Pro Compiler by MicroEngineering Labs. The 
' conversion factors listed in the SRF04 manual are for the PULSIN 
' of a Basic Stamp II which measures in 2us increments. When running
' a PICmicro MCU at 4 MHz and using the PicBasic Pro compiler the
' PULSIN command measures in 10us increments and the PULSOUT command
' also generates pulses with 10us increments. The adjusted conversion
' factors for 10us increments are:
' inches = raw_data / 15
' centimeters = raw_data / 6
'*********************************************************************************************

Include "modedefs.bas"			' Include serial modes

trisa = %00000000			' set porta to outputs
trisb = %00001000			' set portb pin 3 to input

lcd           var PORTA.3			' define variables and constants
piezo       var PORTB.4
trigger      var PORTB.2
echo         var PORTB.3
left_led     var PORTB.0
right_led   var PORTB.1
baud          con N2400
dist_raw     var word
dist_inch    var word
dist_cm      var word
conv_inch    con 15
conv_cm      con 6

low trigger						' set trigger pin to logic 0
low left_led						' turn off left LED
low right_led						' turn off right LED

Serout lcd,baud,[254,1]					' clear lcd screen

pause 1000						' give time to initialize lcd

Serout lcd,baud,[254,128,"- Sonar Ranger -"]		' display program title on the LCD

sound piezo,[100,10,50,5,70,10,50,2]			' Make startup sound
                                               
pause 1000						' wait for 1 second

Serout lcd,baud,[254,128,"inches:         "]		' set up the LCD display

Serout lcd,baud,[254,192,"centimeters:    "]

main:

     gosub sr_sonar					' get sonar reading

     Serout lcd,baud,[254,135,#dist_inch,"   "]		' display the distance in inches

     Serout lcd,baud,[254,204,#dist_cm,"   "]		' display the distance in centimeters

Goto main

end 

sr_sonar:

         pulsout trigger,1				' send a 10us trigger pulse to the SRF04
         pulsin echo,1,dist_raw			' start timing the pulse width on echo pin 
         dist_inch = (dist_raw/conv_inch)		' Convert raw data into inches 
         dist_cm = (dist_raw/conv_cm)		' Convert raw data into centimeters
         pause 1					' wait for 10us before returning to main

return