reading ultrasonic receve

[majorkuso]

I am trying to read the ultrasonic receiver using the pic12f683 I thought about using the pulse out and pulsein command in picbasic pro but how do i change the internal oscillator frequency to drive it to 10us pulse to trigger the receiver

[majorkuso]

I am trying to get the pic to send out a 10us pulse in order to trigger the ultrasonic receiver and then convert it inches to turn on an led or to drive motors help is appreciated

[LinkMTech]

The default clock on the 12F683 is 4MHz according to the datasheet found in REG 3-1 but still better to set it and define it along with turning OFF other peripherals not used:

@ __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF & _BOD_OFF

OSCCON = %01100001  ' Osc 4MHz
ADCON0 = 0          ' A/D module OFF
CMCON0 = 7	    ' Analog comparators off
GPIO = %00000000    ' Turn OFF all ports
TRISIO = %00001101  ' Ports 0, 2 and 3 inputs, rest outputs (Example)

DEFINE OSC 4        ' Declare FOR PAUSE and PAUSEUS statements

But if using PBP3 then:

#CONFIG
    __CONFIG    _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF & _BOD_OFF
#ENDCONFIG

OSCCON = %01100001  ' Osc 4MHz
ADCON0 = 0          ' A/D module OFF
CMCON0 = 7	    ' Analog comparators off
GPIO = %00000000    ' Turn OFF all ports
TRISIO = %00001101  ' Ports 0, 2 and 3 inputs, rest outputs (Example)

DEFINE OSC 4        ' Declare FOR PAUSE and PAUSEUS statements

[majorkuso]

here is the code i may not be understanding the pulse command the sensor is an hc-sr04 thanks for the help

define osc 4
ANSEL = 0 ' set I/O pin to digital
CMCON0 = 7 ' set comparator off
osccon = $60
define osc 4


input GPIO.4 ' set GPIO.4 to input pin 3
OUtput GPIO.2 ' set GPIO.0 to output pin 5
output GPIO.1 ' set GPIO.1 to output pin 6
sens var GPIO.4
led var GPIO.2
trig var GPIO.1
dist var word


main:
gosub distance
low led
while dist < 8
high led
'pause 500
'low led
'pause 500
wend
goto main

distance:
high trig
pauseus 10
low trig
'pulsout trig,2 ' produces 10us pulse
pause 50
pulsin sens,1,dist 'reads echo pulse from sonar
dist= dist/15 'convert to inches
pause 100
return

[LinkMTech]

The PULSIN and PULSOUT commands at 4MHz have a 10us resolution per count.
PULSIN will time out after 65535 counts or 655ms and return a value of 0 (zero) if it doesn't see the expected pulse.

Make sure MCLR setting is OFF or pin 4 pulled HIGH with a 10K or something to keep it out of reset.

Try this code but realize that if the PULSIN times out, the 0 (zero) will turn the LED ON too because it is <8.

ANSEL = 0 ' set I/O pin to digital
CMCON0 = 7 ' set comparator off
osccon = $60
define osc 4

input GPIO.4 ' set GPIO.4 to input pin 3
OUtput GPIO.2 ' set GPIO.0 to output pin 5
output GPIO.1 ' set GPIO.1 to output pin 6
sens var GPIO.4
led var GPIO.2
trig var GPIO.1
dist var word

main:
GOSUB distance    
    IF dist < 8 THEN
        HIGH led
    ELSE
        LOW led
    ENDIF
GOTO main    

distance:
    trig = 0            ' start output in LOW state
    PULSOUT trig,1      ' each count = 10us
    PULSIN sens,1,dist  ' will time out in 655ms if nothing received
    dist= dist/15 'convert to inches
    PAUSE 100
RETURN

END

If you don't want the LED ON when PULSOUT times out then I would use the SELECT CASE:

ADCON0 = 0      ' A/D module OFF
ANSEL = 0 ' set I/O pin to digital
CMCON0 = 7 ' set comparator off
osccon = $60
define osc 4

input GPIO.4 ' set GPIO.4 to input pin 3
OUtput GPIO.2 ' set GPIO.0 to output pin 5
output GPIO.1 ' set GPIO.1 to output pin 6
sens var GPIO.4
led var GPIO.2
trig var GPIO.1
dist var word

main:
GOSUB distance    
    SELECT CASE dist
        CASE 0          ' PULSIN timed out and returns zero, turns LED OFF
            LOW led 
        CASE IS < 8     ' dist <8 inches but not zero, turns ON LED
            HIGH led 
        CASE ELSE       ' dist >8 inches turns LED OFF
            LOW led
    END SELECT
GOTO main    

distance:
    trig = 0            ' start output in LOW state
    PULSOUT trig,1      ' each count = 10us
    PULSIN sens,1,dist  ' will time out in 655ms if nothing received
    dist= dist/15 'convert to inches
    PAUSE 100
RETURN

END

[majorkuso]

thanks I will give it a try I have chuck hellebuyck's book on picbasic are there any other recommendations for it that could better benefit me .

[majorkuso]

ok I tried the case method but when the sensor detects anything within the required distance the led blinks instead of holding steady on

[prstein]

are there any other recommendations for it that could better benefit me .

Chuck Hellebuyck's book is the best commercial basic-to-intermediate PBP book that I've seen. As far as other recommendations:

1. The manual that comes with PB3! There is a wealth of knowledge in there, and it is put together very well. I still find something new every time I look in it--I keep a shortcut for it on the Windows task bar.

2. The manual for whatever PIC you're using. It took me a while to learn how to understand the PIC manuals, it was a post in a precursor to this fine forum (email list) that clicked it for me. Which brings me to...

3. This forum. Use Darrel's excellent improved search tool (here). Commit to reading every new post for a few weeks and get a feel for the common troubles many have, drink in the wisdom of the regular posters (not me), and follow some of the posted code as it gets improved.

Best Regards,
Paul

[majorkuso]

the sensor works, but the led turns off and on rapidly instead of staying on what could be the problem

[LinkMTech]

Hmmmmm.... try putting the trig = 0 before the main loop:

    trig = 0            ' start output in LOW state

main:
GOSUB distance    
    SELECT CASE dist
        CASE 0          ' PULSIN timed out and returns zero, turns LED OFF
            LOW led 
        CASE IS < 8     ' dist <8 inches but not zero, turns ON LED
            HIGH led 
        CASE ELSE       ' dist >8 inches turns LED OFF
            LOW led
    END SELECT
GOTO main    

distance:
    PULSOUT trig,1      ' each count = 10us
    PULSIN sens,1,dist  ' will time out in 655ms if nothing received
    dist= dist/15 'convert to inches
    PAUSE 100
RETURN

END

[majorkuso]

I put the low trig before the main but it still blinks I wonder if the sensor is sending stray numbers when it starts the distance routine, is there a way I can sim the pic in multisim 11? I may try programming another pic and make sure it is not an internal error

[LinkMTech]

You may right about the stray or false triggering as mentioned in the data sheet.
Now try putting a little delay after the PULSOUT to give the device time to complete the transmit function before listening for an echo.

distance:
    PULSOUT trig,1      ' each count = 10us
    PAUSEUS 120      ' Wait for transmit pulse to complete
    PULSIN sens,1,dist  ' will time out in 655ms if nothing received
    dist= dist/15 'convert to inches
    PAUSE 100
RETURN

END

[majorkuso]

ok I tried pause from 50 to 200 milliseconds but it will not respond until I comment the pause command out or remove, it I am wondering if the pic itself is bad internally if so that could explain some erroneous behavior, i have a couple of pic 16f877A coming in and may use them to see if it clears up and then try these later on new 12f683 pics

[LinkMTech]

I have found when I suspect a bad PIC, it turns out that it is just doing what I programmed it to do.

ok I tried pause from 50 to 200 milliseconds but it will not respond until I comment the pause command out or remove

Anyways, 50 to 200ms PAUSE's are way to long to wait since:
Max distance measured is 4M or 157.48 inches
And if I'm thinking straight, that works out to 157*15= 2362 counts
Then with PUSLIN at 10us per increment is 2362*10us = 23.62ms

So 23.62ms will be the maximum time measured for 4 meters. Unless I took a rong tern somewhere in the calculation.

Do you have a scope to see how long it actually takes to complete the pulse transmission?

[majorkuso]

I do I have two analogs and one digital I prefer the analogs , but don't have probes for them I will try to hook it up later and see what the timing is

[languer]

In the code that LinkMTech provided there should be no issue with the PAUSEUS or PAUSE commands.

distance:
PULSOUT trig,1 ' each count = 10us
PAUSEUS 120 ' Wait for transmit pulse to complete
PULSIN sens,1,dist ' will time out in 655ms if nothing received
dist= dist/15 'convert to inches
PAUSE 100
RETURN

END

There is a minimum delay between the time the device reacts to the input (PULSOUT) and the time it provides an output (to be read by PULSIN). This time is defined by the 8 40kHz bursts it sends. The device does not raise its output high before the burst is sent (that is in the datasheet), so that means that you could use an approximate delay no longer than 200us between PULSOUT and PULSIN commands and still be ok. LinkMTech suggested 120us to allow for margin; that should be no problem. The other delay, the one which occurs after the PULSIN, represents how much to delay before the next time it tries the measurement again. This again should not be an issue.

You certainly need a scope, but not to test your code (since your code looks fine, and it matches BASIC STAMP code and many others which work with modules like the PING, and Devantech's SRF04 modules. You need the scope to see if the module you have is doing what its datasheet claims it does. Also. maybe a pulldown (say 10-20k on the GPIO4 may help - perhaps the SR module does not pull to ground too well).

[majorkuso]

Well the problem was the breadboard I was developing on the configuration works fine on a different one so I am chalking it up to good ole conductivity. sometimes it is the simple things that get you

[LinkMTech]

Ahhh, son of a garbanzo beans!
Well glad to hear you got it fixed and on your way to becoming an expert.

[majorkuso]

thanks for the help guys