12F629 CONFIG

siliconchip · Post by **siliconchip** » Thu Dec 07, 2017 2:47 pm

hi all ive been away from flowcode and electronics for a while and decided to get back with it by programming a 12F 629 which would simply light a led at 1HZ but ive only managed to permanately light the led, ive looked at the datasheet and messed with the OSCCAL settings but on reflection I'm not sure I need to touch this any pointers to guide me would be appreciated

cheers in advanced bob

Post by **LeighM** » Thu Dec 07, 2017 4:50 pm

Can't say I'm familiar with this chip, but in the config you have "RC clock out" and looking at the datasheet it looks like clock out is on the same pin as you have chosen for the LED. So maybe there is a permanent clock out that is activating the LED.

siliconchip · Post by **siliconchip** » Thu Dec 07, 2017 6:08 pm

hi leigh thanks for the reply, the output I used was because of the clock out thinking it would flash the led, I tried no clock out but the led didn't lite

siliconchip · Post by **siliconchip** » Thu Dec 07, 2017 8:23 pm

right after playing around abit more I'm now using GP0 as the output and hay presto the led flashes, BUT as I understand it GP4 can be used as an output how do I manage this ive looked through the data sheet and cant find the answer

Post by **Benj** » Thu Dec 07, 2017 9:24 pm

Hello,

On some of the earlier PIC devices you need an external pull up resistor for pin A4/GP4. The pin can sink current to ground (output low) but cannot source current (output high). I think this is often called an open collector configuration. If you're driving an LED then try wiring in the active low configuration and that should work as expected.

siliconchip · Post by **siliconchip** » Thu Dec 07, 2017 9:52 pm

Hi benj thanks for the reply i shall give it ago and see what happens

Post by **Benj** » Thu Dec 07, 2017 10:36 pm

Hmm, Just checked the 629 datasheet and the pin GP4 seems fully featured. I'll have a dig and see if anything comes up.

siliconchip · Post by **siliconchip** » Fri Dec 08, 2017 8:48 am

hi benj ive been looking on youtube and found that GP4 when using internal oscillator clockout provides a 1MHz pulse at this pin I believe which would probably mean why my LED on this port is always on which initially gave me the impression it wasn't flashing, if this is the case I guess this when configured as an output and with this oscillator config it would be used as a clock source to drive some other part of circuitry ???

Post by **LeighM** » Fri Dec 08, 2017 9:24 am

That's what I was trying to tell you in #2

Have you tried changing the config? ...

: no_clock.jpg (65.36 KiB) Viewed 4470 times

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