How to check oscillator frequency

[Johan]

Hi all,

I'd like to know how to check that the osccilator is working as requested. I mean how do I know exactly that the external crystal is working at 8 Mhz

I made some experiment with 18F4431, the program run well with internal oscilator setup 4Mhz, but it does not function when I switch to external crystal
I am using easypic 4 board.

Thanks,

Johan

[skimask]

Hi all,
I'd like to know how to check that the osccilator is working as requested. I mean how do I know exactly that the external crystal is working at 8 Mhz
I made some experiment with 18F4431, the program run well with internal oscilator setup 4Mhz, but it does not function when I switch to external crystal
I am using easypic 4 board.
Thanks,
Johan

Are you sure the config bits are set correctly in your program?

[Johan]

What config bits needed to set up ?
This is my test program , please correct if it is not correct:

\code
TRISA = %11111111 ' Set PORTA to all input
TRISB = %00000000 ' Set PORTB to all output
TRISC = %00000000 ' Set PORTC to all input
TRISD = %00000000 ' Set PORTD to all output
TRISE = %00000000 ' Set PORTE to all output
ANSEL0= %00000000 ' Analog channel AN0-AN7 off
ANSEL1= %00000000 ' Analog channel AN8 off

clear

main:
high portb.1
pause 1000
low portb.1
pause 1000
goto main

\code

the oscillator setting during programming with picflash is:
oscillator : int ra6 & ra7 as i/o
other setting left unchanged

thanks

[mister_e]

yeah... it run but the default OSC speed is set to 32KHz

just add those

OSCCON= %01100000       ' configure internal OSC  @ 4MHZ
While OSCCON.2=0 : wend ' wait until OSC is stable

at the top of your code.

For the configuration bits, it's usual and recommended to set them in your code, have a look at the following...

http://www.picbasic.co.uk/forum/showthread.php?t=543

and here's a short example for a 18F2431, as inspiration source

        '
        '       Pic Configuration
        '       =================
        ASM         
        __CONFIG _CONFIG1H, _OSC_IRCIO_1H  & _FCMEN_OFF_1H & _IESO_OFF_1H
        __CONFIG _CONFIG2L, _PWRTEN_ON_2L & _BOREN_ON_2L & _BORV_45_2L
        __CONFIG _CONFIG2H, _WDTEN_OFF_2H & _WINEN_OFF_2H 
        __CONFIG _CONFIG3L, _T1OSCMX_OFF_3L & _HPOL_LOW_3L & _LPOL_HIGH_3L & _PWMPIN_OFF_3L
        __CONFIG _CONFIG3H, _MCLRE_ON_3H
        __CONFIG _CONFIG4L, _LVP_OFF_4L & _DEBUG_OFF_4L
        ENDASM
        DEFINE OSC 4

Now if you want to switch to the external OSC, use...

        ASM         
        __CONFIG _CONFIG1H, _OSC_HS_1H  & _FCMEN_OFF_1H & _IESO_OFF_1H
        __CONFIG _CONFIG2L, _PWRTEN_ON_2L & _BOREN_ON_2L & _BORV_45_2L
        __CONFIG _CONFIG2H, _WDTEN_OFF_2H & _WINEN_OFF_2H 
        __CONFIG _CONFIG3L, _T1OSCMX_OFF_3L & _HPOL_LOW_3L & _LPOL_HIGH_3L & _PWMPIN_OFF_3L
        __CONFIG _CONFIG3H, _MCLRE_ON_3H
        __CONFIG _CONFIG4L, _LVP_OFF_4L & _DEBUG_OFF_4L
        ENDASM
        DEFINE OSC 8

and remove the OSCCON & WHILE : WEND lines

[Johan]

Thank you Mr.E,

On my programmer's setup page ( easypic ) there are configuration bits to setup ( see attachment ) . If I put the configuration at PBP, will this be a problem ?

[mister_e]

Nope, there's no problem at all. In fact, if you set the bits in your code, you'll no longer need to set them in Picflash as they're now included in the .HEX file.

Try the above, a click on 'Reload HEX'. You'll see that the Oscillator bit have change to HS or INT RC... depending which code above you have used.

I also have that board. Can't live without now

[Johan]

Mr.E,

I tried to put those asm lines, and got error messages :
Error 118 bla,bla,bla : Overwriting previous address content

But my problem is solved just by adding : define OSC 8