How to generate 40MHz pulse with PWM command for my ultrasonic transmitter..please

[mackrackit]

Let the weeding begin...

It will be great when Bruce finishes his book. I will be doing some weeding then too

[skimask]

It will be great when Bruce finishes his book. I will be doing some weeding then too

$20 says that even when Bruce does finish the book, we'll still be answering the same questions over and over and over...and not because of a lack of information from the book.
Maybe Bruce can include a couple of hands with each book.. ya know, for the user to hold while messing around with the PICs.

[Picstar]

I am working with the following code using the lcd to display distance with the Ping sensor.
I am using the QL200 development board, so my DEFINE statements may be different or un-needed for you. My problem is that the ping sensor works,( I can see it on my oscilloscope),
but I cannot get a reading on my lcd. Only 0.
Any help would be appreciated!.

' File......sonar1.pbp
' Microcontroller used: Microchip Technology 16F887
'--------Program Desciption--------
' Using the ping ultrasonic range finder,
' the distance from the range finder to an object
' is displayed on an LCD screen in inches.
' rb0 is signal in/out
define osc 4
adcon1 = %00000000
define lcd_dreg portd
define lcd_dbit 4
define lcd_ereg porta
define lcd_ebit 3
dist var byte
range var word
inches CON 15 'Assigns the value 15 conversion
pause 2000

sonar 'Pulse Width
pulsout 0,20
pauseus 100
pulsin 0,10,range
dist = range/inches 'Converts raw sonar reading to inches
LCDOUT $FE,1,"Distance"
LCDOUT $FE,$14,#range
PAUSE 2000
GOTO sonar
END

[Ioannis]

Try the DEIFINE's in capital.

Ioannis

[Picstar]

Tried capitalizing Define's but to no avail, you're right though they are supposed to be in capitol. Any other ideas??

[Picstar]

You're right missing : in sonar label. According to the specs on the ping unit, there is a 750us pause called a "holdoff?". At any rate, I have tried it without a pause and have changed timing in the pulsin and pulsout commands, but still no luck. Using PBP 2.50b. heres the latest code:


' File......sonar1.pbp
' Microcontroller used: Microchip Technology 16F887
'--------Program Desciption--------
' Using the ping ultrasonic range finder,
' the distance from the range finder to an object
' is displayed on an LCD screen in inches.
' rb0 is signal in/out
adcon1 = %00000000
define LCD_DREG PORTD
define LCD_DBIT 4
define LCD_EREG PORTA
define LCD_EBIT 3
dist var byte
range var byte
inches CON 15 'Assigns the value 15 conversion
pause 2000

sonar: 'Pulse Width
pulsout portb.0,20
pulsin portb.0,100,range
'dist = range/inches 'Converts raw sonar reading to inches
LCDOUT $FE,1,"Distance"
LCDOUT $FE,$14,#range
PAUSE 2000
GOTO sonar
END

[skimask]

Re-read the manual on the use of the pulsin statement.

You say the unit has a 'holdoff' of 750us, and yet you originally used a pauseus of 100. What's up with that?

[skimask]

The define, in this case, won't make any difference since it's define osc 4, which is PBP default...

sonar   'Pulse Width

How does that work? Is it a label? Is it a command? Is it a comment?

pulsout 0,20
pauseus 100
pulsin 0,10,range

You wait for 100us instead of going straight to looking for a return pulse? How does THAT work? Shouldn't you jump directly to looking for the return pulse?
Which version of PBP are you using?