Hel programing Devantech SRF04 Ultrasonic Range Finder to measures distances to

hvilla01

Hi all,

I try the example that is at http://www.acroname.com/robotics/info/examples/srf04-1/srf04-1.html

' {$STAMP BS2}
' {$PBASIC 2.5}
'
'
' Devantech SRF04 Example
'
wDist VAR Word
INIT CON 0
ECHO CON 1

' CONVERSION FACTORS:
'
' The PULSIN command returns the round-trip echo time in 2us units
' which is equivalent to the one-way trip time in 1us units.
'
' distance = (echo time) / (conversion factor)
'
' use 74 for inches (73.746us per 1 in)
' use 29 for centimeters (29.033us per 1 cm)
'
convfac CON 29 ' use inches


'

---

main:
······· GOSUB sr_sonar
······· DEBUG DEC wDist, CR
······· PAUSE 200
······· GOTO main

sr_sonar:
······· PULSOUT INIT,5 ' 10us init pulse
······· PULSIN ECHO,1,wDist ' measure echo time
······· wDist=wDist/convfac ' convert to inches
······· PAUSE 10
······· RETURN
sr_sonar_2:
······· PULSOUT INIT,5 ' 10us init pulse
······· OUTPUT INIT ' dummy command (delay)
······· RCTIME ECHO,1,wDist ' measure echo time
······· wDist=wDist/convfac ' convert to inches
······· PAUSE 10
······· RETURN
END

And the only thing I receive is a repited 0 on the debug screen, what I want to do is to move two servos forward until the SFR04 detects object
aprox at 4 or 5 cm, any help will be really apriciated.

Humberto
·

Unsoundcode

Humberto, I think the first line of code in the main: routine should read ....GOSUB sr_sonar_2: . This routine uses RCTIME (not PULSIN) to measure the time taken for the pulse to echo back to your reciever, the next line divides that time by the conversion factor.

Jeff T.

hvilla01

Hi Jeff,

Thanks for your promp response, I tried what you tolb but it shows an error (Undifined label), I am jusr srating using BS2.
Here is my code with tha cange you suggest

' {$STAMP BS2}
' {$PBASIC 2.5}

'
'
' Devantech SRF04 Example
'

wDist VAR Word

INIT CON 0
ECHO CON 1


' CONVERSION FACTORS:
'
' The PULSIN command returns the round-trip echo time in 2us units
' which is equivalent to the one-way trip time in 1us units.
'
' distance = (echo time) / (conversion factor)
'
' use 74 for inches (73.746us per 1 in)
' use 29 for centimeters (29.033us per 1 cm)
'

convfac CON 29 ' use inches





'

---

main:

GOSUB sr_sonar:
DEBUG DEC wDist, CR
PAUSE 200
GOTO main


GOSUB sr_sonar_2:

PULSOUT INIT,5 ' 10us init pulse
PULSIN ECHO,1,wDist ' measure echo time
wDist=wDist/convfac ' convert to inches
PAUSE 10
RETURN

sr_sonar_2:

PULSOUT INIT,5 ' 10us init pulse
OUTPUT INIT ' dummy command (delay)
RCTIME ECHO,1,wDist ' measure echo time
wDist=wDist/convfac ' convert to inches
PAUSE 10
RETURN
END

All I need is the sensor tell me whan is about 3 to five cm so I can stop the servos.
Thanks a lo I hope there is not to much trouble, any help will be realy apriciated.

Humberto

Unsoundcode

Humberto, you altered the wrong line of code, undo what changes you made and make this change.

where it says:

main:

GOSUB sr_sonar

change to:

main:

GOSUB sr_sonar_2

Jeff T.

hvilla01

Hi Jeff I did what you told me and the result is the same *in the devug screen unli shows 0
0
0

And thats all, I connect my SRF04 like this

GRD VSS
UNUSED
INIT P0
EDCHO P1
V+ VDD

This is the program with your changes

' {$STAMP BS2}
' {$PBASIC 2.5}

'
'
' Devantech SRF04 Example
'

wDist VAR Word

INIT CON 0
ECHO CON 1


' CONVERSION FACTORS:
'
' The PULSIN command returns the round-trip echo time in 2us units
' which is equivalent to the one-way trip time in 1us units.
'
' distance = (echo time) / (conversion factor)
'
' use 74 for inches (73.746us per 1 in)
' use 29 for centimeters (29.033us per 1 cm)
'

convfac CON 74 ' use inches





'

---

main:

GOSUB sr_sonar_2:
DEBUG DEC wDist, CR
PAUSE 200
GOTO main


GOSUB sr_sonar_2:

PULSOUT INIT,5 ' 10us init pulse
PULSIN ECHO,1,wDist ' measure echo time
wDist=wDist/convfac ' convert to inches
PAUSE 10
RETURN

sr_sonar_2:

PULSOUT INIT,5 ' 10us init pulse
OUTPUT INIT ' dummy command (delay)
RCTIME ECHO,1,wDist ' measure echo time
wDist=wDist/convfac ' convert to inches
PAUSE 10
RETURN
END


Regards

Unsoundcode

Humberto, sorry that didn't work out for you. Parallax have a very detailed explanation of how to implement the SRF04 this is one link to that information http://www.acroname.com/robotics/parts/R93-SRF04p.pdf

good luck

Jeff T.

doug.taylor

Just a quick observation. You have a colon after the tag name in your GOSUB statements. The colon only goes after the tag name when it is used as a tag.


GOSUB mytag

mytag:
RETURN

hvilla01

Hi Doug,

I tried the program that came at http://www.acroname.com/robotics/parts/R93-SRF04p.pdf and it works great, I hope it not to much trouble but I dont know where to put on the program that if thr SRF04 reads and object then stop go back turn and the go forward.

Regards
Humberto

hvilla01

Hi,

What I need is when the SRF04 reads an object at 4 cm to stop the servos and go back few cms and then tern and go forward.

Regards
Humberto

Franklin

The program should do this.. move forward, check distance, if distance < 4cm stop, backup, turn left(or right), go forward. Most of this code is in the pdf about the boe-bot and works fine. I used this code to have my boe-bot move until it sensed and object and then swivel the srf until it found the most open direction and then head that way.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- Stephen

hvilla01

Thank's Stephen but this will work with the SRF04?

hvilla01

Hi,
I still can make the program to work properly, if any one can help it will be great,
This is the program

' =========================================================================
'
' File....... SRF04_Demo.BS2
' Purpose.... Devantech SRF04 Ultrasonic Range Finder
' Author..... Parallax, Inc. (Copyright 2003 - All Rights Reserved)
' E-mail..... support@parallax.com
' Started.... 06 MAR 2002
' Updated.... 01 OCT 2003
'
' {$STAMP BS2}
' {$PBASIC 2.5}
'
' =========================================================================


'

---

[noparse][[/noparse] Program Description ]

---

'
' This program uses the Devantech SRF04 to measure the distance between the
' unit and a target. Display is raw value, centimeters, and inches.


'

---

[noparse][[/noparse] Revision History ]

---

'
' 01 OCT 2003 : Updated for PBASIC 2.5 and for any BASIC Stamp module


'

---

[noparse][[/noparse] I/O Definitions ]

---

'
Trigger PIN 0
Echo PIN 1


'

---

[noparse][[/noparse] Constants ]

---

#SELECT $STAMP
#CASE BS2, BS2E
Trig10 CON 5 ' trigger pulse = 10 uS
ToCm CON 30 ' conversion factor to cm
#CASE BS2SX, BS2P
Trig10 CON 13
ToCm CON 78
#CASE BS2PE
Trig10 CON 5
ToCm CON 31
#ENDSELECT


'

---

[noparse][[/noparse] Variables ]

---

samples VAR Nib ' loop counter
pWidth VAR Word ' pulse width from sensor
rawDist VAR Word ' filtered measurment
cm VAR Word ' centimeters
inches VAR Word
pulsecount VAR Byte

'

---

[noparse][[/noparse] EEPROM Data ]

---

'

---

[noparse][[/noparse] Initialization ]

---

Setup:
LOW Trigger
DEBUG CLS,
"Devantech SRF04 Demo", CR,
"

---

", CR,
"Raw........... ", CR,
"Centimeters... ", CR,
"Inches........ "


'

---

[noparse][[/noparse] Program Code ]

---

Main:
DO
GOSUB Forward_Pulse
GOSUB Get_Sonar ' take sonar reading
DEBUG CRSRXY, 15, 2, DEC rawDist, CLREOL
cm = rawDist / ToCm ' convert to centimeters
DEBUG CRSRXY, 15, 3, DEC cm, CLREOL
IF cm < 100 THEN
GOSUB Back_Up
GOSUB Turn_Left
ELSE

RETURN
ENDIF
inches = cm */ $03EF ' x 3.937 (to 0.1 inches)
DEBUG CRSRXY, 15, 4,
DEC inches / 10, ".", DEC1 inches,
CLREOL

PAUSE 10 ' delay between readings
LOOP

END
Forward_Pulse:
FOR pulseCount = 0 TO 50
PULSOUT 13, 1000
PULSOUT 12, 650
PAUSE 15
NEXT
RETURN



Back_Up:
FOR pulseCount = 0 TO 50
PULSOUT 13, 650
PULSOUT 12, 850
PAUSE 15
NEXT
RETURN

Turn_Left:
FOR pulseCount = 0 TO 50
PULSOUT 13, 650
PULSOUT 12, 650
PAUSE 15
NEXT
RETURN

Turn_Right:
FOR pulseCount = 0 TO 50
PULSOUT 13, 850
PULSOUT 12, 850
PAUSE 15
NEXT
RETURN





'

---

[noparse][[/noparse] Subroutines ]

---

Get_Sonar:
rawDist = 0 ' clear measurement
FOR samples = 1 TO 5 ' take five samples
PULSOUT Trigger, Trig10 ' 10 uS trigger pulse
#SELECT $STamp
#CASE BS2, BS2E
RCTIME Echo, 1, pWidth ' measure pulse
#CASE #ELSE
PULSIN Echo, 1, pWidth ' measure pulse
#ENDSELECT
rawDist = rawDist + (pWidth / 5) ' simple digital filter
PAUSE 10 ' minimum period between
NEXT
RETURN