Newbie need Help 16F627a

[Bruce]

Kind of sounds like you left the /MCLR pin floating.

[Archangel]

Kind of sounds like you left the /MCLR pin floating.

DOH ! I missed that one . .

[azmax100]

Hi all.
thanks for the reply.
Joe S. I'm using 20mhz xtal. After Define still the same.

Bruce what should i do with the MCLR pin. I am totally zero with PIC but have some experience with BS2.

[Archangel]

Hi all.
thanks for the reply.
Joe S. I'm using 20mhz xtal. After Define still the same.

OK 20 mhz will not work with the default config statement, to use 20 mhz you must change it or comment it out of the PIC16F627A.INC file located in the PBP Directory. The Default config is set to use XT_OSC and the 20 mhz requires HS_OSC, what it does internaly is to provide the oscillator with more power, as it is needed to run that fast. Study this link : http://www.picbasic.co.uk/forum/showthread.php?t=543 As for the MCLR PIN tie a resistor about 5k ohm from mclr to thr 5v+ supply. To reset the PIC you then momentaraly ground it, OR in the config statement you turn it off and use it as an I/O.

[azmax100]

Joe S.
After editing the INC file in PBP I got this message

Error [113] c:\pbp\16f628.inc 22 : Symbol not defined (_HC_OSC)

For your info I'm using 16F628 now cause i broke some of the 16F627a pin while
remove it from my icsp.

Theres already a 10k resistor and a diode in series on my icsp module.

The LED blink when i touch the osc pin.

here's my code:
DEFINE OSC 20
CMCON = 7
OPTION_REG.7 = 0



TRISB.0 = 0
LED VAR PORTB.0 ' alias PORTB.0 to LED

loop:
high LED' turn on LED connected to PORTB.0
Pause 500 ' delay for .5 seconds

low LED ' turn off LED connected to PORTB.0
Pause 500 ' delay for .5 seconds

GoTo loop ' loop and blink LED forever

[azmax100]

I got my LED to blink. Problem solve. This is my first lesson. Under microcode studio compile and program option I uncheck the MPASM option. I should not use the MPASM compiler.

For other newbies please learn from my mistake.

Thanks to all the forum members.

[Bruce]

Hi azmax100,

FYI it really should work with either MPASM or the PM assembler. Look in your 16F628.INC and see if all config options are the same for both the PM & MPASM config settings.

It may be that you have some config options set different in the MPASM config line.

For example - say your 16F628.INC file has something like this

  NOLIST
    ifdef PM_USED
        LIST
        include 'M16F62x.INC'   ; PM header
        device  pic16F628, hs_osc, wdt_on, pwrt_on, mclr_off, lvp_off, protect_off
        XALL
        NOLIST
    else
        LIST
        LIST p = 16F628, r = dec, w = -302
        INCLUDE "P16F628.INC"   ; MPASM  Header
        __config _XT_OSC & _WDT_ON & _PWRTE_ON & _MCLRE_ON & _LVP_OFF & _CP_OFF
        NOLIST
    endif
        LIST

Now let's say you're using the default PM assembler & not MPASM. When you compile, PBP knows you're using the PM assembler, so it uses these configuration settings --

device pic16F628, hs_osc, wdt_on, pwrt_on, mclr_off, lvp_off, protect_off

With a 20MHz crystal, you want/need the hs_osc setting. If you do not have a pull-up resistor on the PIC /MCLR pin, you also want the mclr_off setting.

Why? Because HS_OSC provides a higher drive level required by the higher speed 20MHz crystal. XT_OSC provides a lower drive level, which may or may not work.

MCLR_OFF turns OFF the external reset function on the /MCLR pin, so the external pull-up resistor isn't necessary.

Now, let's say you have no external pull-up, and you're using the 20MHz crystal, and you switch to use the MPASM asembler.

Again, when you compile, PBP will now know you're using the MPASM assembler, and it will now use the config settings shown above that look like this --

__config _XT_OSC & _WDT_ON & _PWRTE_ON & _MCLRE_ON & _LVP_OFF & _CP_OFF

Now it doesn't work because you have _XT_OSC (which doesn't provide enough drive to work with your 20MHz crystal), and you have the reset function enabled for the /MCLR pin with no pull-up to Vcc, and /MCLR is floating.

That would for sure cause erratic behaviour.

Just FYI. Config settings make a BIG difference.

[Archangel]

Joe S.
After editing the INC file in PBP I got this message

Error [113] c:\pbp\16f628.inc 22 : Symbol not defined (_HC_OSC)

For your info I'm using 16F628 now cause i broke some of the 16F627a pin while
remove it from my icsp.
Theres already a 10k resistor and a diode in series on my icsp module.
The LED blink when i touch the osc pin.

Hi Azmax100,
First off, Congratulations on your sucess, It is so irritating to pour your time and effort into a project and it does not work as expected.
I have commented out the default config statements for the chips I use most often and always insert the config statement into my code.
This gives me flexibility to quickly change things like OSC, WDT, MCLR, BOD, and I never have to go hunt for the config settings in another file.

[azmax100]

Bruce
Thanks for the time explaining. I've spend three days just to make the LED to blink. I've experienced with Basic stamp 2. I know it's a little bit harder to play with PIC but I am willing to learn.
I will start a robotic project shown by you in rentron.com. For sure the will be a lot of of (silly) question. he he
Anyhow thanks to you and Joe s.