Stupid simple question.....

[Darrel Taylor]

For a 12F683, you need to turn off the Analog inputs and Comparator.

SYMBOL ANSEL = $9F
SYMBOL CMCON0 = $19

POKE ANSEL, 0
POKE CMCON0, 7

hth,

[chien_fu]

I cannot express enough gratitude. It works! Thank you so much kind sir. Now where might one learn a bit of information like that? That seems fairly basic, but I don't recall coming across that in any of my "pic'n" books or the 12F datasheet...

[HenrikOlsson]

Hi,
If you look at section 4 in the datasheet you'll see a note there saying:

Note: The ANSEL and CMCON0 registers must be initialized to configure an analog channel as a digital input. Pins configured as analog inputs will read ‘0’.

There's also an example showing how to do it but it's in ASM so it's not that easy to understand.

If you then look at figure 8.4 you'll see the various configurations for the comparator module and in the bottom right hand corner it shows that you should write 7 (the three lower bits are set) to CMCON0 in order to disable the comparator.

If you then look at the bottom of table 2.2 it'll show you that ANSEL "comes up" with the lower 4 bits set and if you look at register 4-3 (page 33) you'll see that when bit 0-3 is set it means that the pin is in "analog mode".

As for the rest, $9F is the adress for ANSEL register and $19 is the adress for the CMCON0 register and that can be found if you look at figure 2.2 in the same datasheet. PBP makes it a lot easier as it allows you to write directly the the registers without having to look up the actual adress of it "manually".


It's a very common thing to overlook untill you've been bitten by it, next time a pin doesn't work as you think it should it'll be the first thing you'll think of checking ;-)

/Henrik.

[chien_fu]

oy...
Thanks guys, you rock..
How I wish I could be using my Arduino for this project..

[chien_fu]

I really hate this stuff.... it makes me want to stab myself in the eyeball with a fork.

I'm measuring 3v from Pin1 (GP1) on my 12F683.
I'm using a 3v coin cell. It measures 3v.
I connect a LED to Pin1, it lights.
YAY! Next frickin challenge....

I connect a small vibe motor to my 3v battery, it vibrates like crazy. Yay.
I connect my small vibe motor to Pin1 (measuring 3v) It does absolutely nothing.
I connect the LED to Pin1.. it lights..
I connect the motor to Pin1 ... it does nothing
I punch stuff... that doesn't help.

I don't know what else to try...
The vibe motor draws about 35-40mA

I see that the IO pins supply 25 mA but the GPIO can supply 90mA...
What's the difference?

[ScaleRobotics]

The vibe motor draws about 35-40mA

I see that the IO pins supply 25 mA but the GPIO can supply 90mA...
What's the difference?

A single pin can put out a max of 25mA, but the entire GPIO (all output pins) can put out a max of 90mA. You could use a transistor, or you could have two pins control the motor (and hope start current would not be too high).

[chien_fu]

So I tried driving it with two pins but something else is screwy now....

This is what I have:

OUTPUT Pin1
output Pin2

Startup:

for startupalarm = 1 to 4
high 2 
high 1 
pause 5000
low 2 
low 1 
pause 5000
next startupalarm

It seems that "high 2" does not actually switch the pin high, but just ticks it high for a split second. "high 1" switches the pin high and it is held high for 5 seconds until it is switched low...

This is the same regardless of which pins I use. The line of code immediately preceding the pause command works, all others do not. Nothing else is connected to the chip, it's all by itself on a breadboard.............