12F683 - how to set it to use external 4 MHz clock?

[mehmetOzdemir]

OPEN YOUR PBP FOLDER AND FIND 12F683.INC

YOU WILL SEE

NOLIST
    ifdef PM_USED
        LIST
        include 'M12F683.INC'	; PM header
        device  pic12F683, intrc_osc_noclkout, wdt_on, mclr_on, protect_off
        XALL
        NOLIST
    else
        LIST
        LIST p = 12F683, r = dec, w = -302
        INCLUDE "P12F683.INC"	; MPASM  Header
        __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_ON &_CP_OFF
        NOLIST
    endif
        LIST

CHANGE THE RED PART AFTER ELSE TO THIS ;

NOLIST
    ifdef PM_USED
        LIST
        include 'M12F683.INC'	; PM header
        device  pic12F683, intrc_osc_noclkout, wdt_on, mclr_on, protect_off
        XALL
        NOLIST
    else
        LIST
        LIST p = 12F683, r = dec, w = -302
        INCLUDE "P12F683.INC"	; MPASM  Header
        __config _XT_OSC & _WDT_ON & _MCLRE_ON & _CP_OFF
        NOLIST
    endif
        LIST

AND YOU DONT NEED TO WRITE "@ DEVICE" STATEMENT AT THE BEGINNING OF YOUR CODE ANYMORE.

[jimbostlawrence]

Excellent!!! I was just reading another persons similar problem and was trying to track it down. Many thanks for that. It does indeed now compile and MPLAB IDE lets me upload the code to the PIC.

Out of interest, is there any way that I can check if the thing has actually switched to the external oscillator [short of removing the oscillator!] by looking at the assembler file?

Many thanks all for help with this - has been bugging me for hours!

[mackrackit]

COOL!!!
You are using MPLAB!!!!
Tool bar - configure - configuration bits.
That shows the current sttings.

[jimbostlawrence]

Haha, you make it sound soooooooooo easy :P

'XT' Cheers

I was hoping that this would help with my serial comm's issue but it hasn't lol. Maybe try another PIC, one with a serial interface built in perhaps?!

I'll persist with this PIC for now and try to do some error-checking handshaking.

I can say that I've definitely learned something today

Best regards to all

J.

[mackrackit]

Now that the configs seem to be worked out, post your code and tell what is happening or not happening and we will see what can be done about it.

[jimbostlawrence]

Hi there,

I think I was having a Friday moment. It all seems to be working very well now that it's using the external osc'. I've even bumped up the baud rate to 9600 and getting a good response. Just putting together a simple algorithm to take input over the serial but and set the pulse frequency/duty cycle for HPWM via Hyperterminal.

Many thanks all for all your help. When I get the code done I'll post it on here as a working version. Won't be long.

Cheers

J.

[jimbostlawrence]

Hi again,

Ok, not the most elegant piece of code, but it works. Basically this allows you to instruct the 12F683 to output a regular pulse at a desired frequency or duty cycle on pin 5. You can communicate with the chip via a serial com port [I'm using a USB to RS232 converter].

Personally, I establish a connection with hyperterminal that comes with XP.
Press 'f' to set frequency [press enter after you type a value in Hz]
Press 'f' to set the dutycycle (0 - 100%) [+enter] - the program will auto scale it 0 - 255.

Or alternatively, type 'f?' or 'd?' to determine the current set dutycycle of frequency.

Note: There is little in the way of error checking on the input. I just wanted to get this back to you guys to show what I'd done and that I was grateful for your help last Friday. Now that I have reliable 2-way com's on the serial bus, I'll set it up with a nice little application in MatLab.

Best regards, J.

P.S. One thing I couldn't sort out was clearing the screen at the start in hyperterminal from the serial port. People say to use Esc/[2J or something but I can't get it to work!!!


Include "modedefs.bas"
ANSEL=0
CMCON0 = %00000111
define osc 4

Serial_out var gpio.0
Serial_in var gpio.1
command var byte
input_char var byte
pulse_width var word
pulse_width_percent var byte
pulse_width_percent_new var byte
pulse_frequency var word
pulse_frequency_new var word
variable_output var word

pulse_width = 128
pulse_width_percent = 50
pulse_frequency = 20000

pause 100
serout Serial_out,T9600,[13]
pause 100
serout Serial_out,T9600,[13," "]
pause 100
SEROUT Serial_out,T9600,[13,"This is a test",13,10]
SEROUT Serial_out,T9600,[13,"f for frequency",13,10]
SEROUT Serial_out,T9600,[13,"d for dutecycle (0-100)",13,10]
SEROUT Serial_out,T9600,[13,"Press ? after f/d to find current value",13,10]

mainloop:

Serin Serial_in,T9600,command

If (command = 100) then
SEROUT Serial_out,T9600,["Enter duty cycle : "]
input_char = 0
pulse_width_percent_new = 0
while input_char<10
pulse_width_percent_new = (pulse_width_percent_new * 10) + input_char
gosub getchar
wend
if input_char <> 15 then
pulse_width = pulse_width_percent_new * 256 / 100
hpwm 1,pulse_width,pulse_frequency
SEROUT Serial_out,T9600,[10,13]
else
SEROUT Serial_out,T9600,[#pulse_width_percent,10,13]
endif
pulse_width_percent = pulse_width_percent_new
endif

If (command = 102) then
SEROUT Serial_out,T9600,["Enter frequency cycle : "]
pulse_frequency_new = 0
input_char = 0
while input_char<10
pulse_frequency_new = (pulse_frequency_new * 10) + input_char
gosub getchar
wend
if input_char <> 15 then
pulse_frequency = pulse_frequency_new
hpwm 1,pulse_width,pulse_frequency_new
SEROUT Serial_out,T9600,[10,13]
else
SEROUT Serial_out,T9600,[#pulse_frequency,10,13]
endif
endif

Goto mainloop

getchar:
serin Serial_in,T9600,input_char
input_char = input_char - 48
if input_char < 10 then
serout Serial_out,T9600,[48+input_char]
endif
return