Turns out it was an issue with wiring the reset pin, although I will
investigate using _MCLRE_OFF, but it doesn't hurt in my usage to not have
the RA5 pin available. I'm getting the high programming voltage from the
PicKIT2.
Thanks for the assistance. (And I will probably reverse the drives of my
LEDs to be sinking to the pic instead, thanks for the tip).
On Sun, Nov 24, 2013 at 6:50 AM, Richard Gray
<rich...@reallyrathergood.com>wrote:
> These are just some thoughts that spring to mind, so don't take me too
> seriously...
>
> 1. Digital output pins on PICS are usually programmable as either inputs or
> outputs, and they default to inputs.
>
> 2. Most digital IC's, regardless of what they do can sink more than they
> can
> source. So, an LED to ground might not be such a good idea as turning it
> around
> and running it from the positive rail, although the sense is reversed of
> course. What you have described might be working, but the LED is lighting
> so
> weakly that you cannot see it - 10k is a bit big. A 'scope or good high
> impedance DMM might be a better tool.
>
> 3. Check that your oscillator is actually oscillating, if you can. A scope
> is
> handy here, again.
>
> 4. So many people omit to do this: I know that C is preferable to assembly
> language, but have a look at the assembler output from the compiler and
> then
> have a look to see if the instructions being emitted make sense. You might
> find
> that you're just writing to memory locations rather than doing any real
> I/O,
> for example. What you're trying to do here should only amount to a few
> instructions, so check that these are correct.
>
> Just thoughts, but (4) is very worthwhile. It's a while since I played with
> PICs, but they're a bit quirky and you have to go through the motions to
> check
> that you're not doing something daft.
>
> On Sunday 24 November 2013 12:07:13 Michael du Breuil wrote:
> > I'm confident its user error, but I seem to be unable to program my
> > PIC16F628A (it's my first foray into the world of PICs, been working with
> > arm M4's). All I'm trying to do is turn on LED outputs, but I this
> doesn't
> > seem to be working. I'm trying to use the internal 4MHz oscillator, all
> the
> > port A and B pins (so everything except for VDD and VSS) are connected
> to a
> > 10K resistor and LED. This is all done on a breadboard, so it's possible
> > there is an error in the wiring, but it appears to be correct.
> >
> > I'm using a PicKIT 2 to program it (and it can correctly auto identify
> the
> > device as a PIC16F628A) and believes it successfully flashes the device.
> > This leads to me to believe I have a good chip, and the ICSP worked out
> > correctly.
> >
> > I'm attempting to build with SDCC, with the appended code, but I don't
> get
> > any thing on any of the output pins, it simply sits there after power on.
> > Are there any obvious errors here?
> >
> > Thanks for your time.
> >
> >
> >
> ///////////////////////////////////////////////////////////////////////////
> > ////////// #include "pic16f628a.h"
> >
> > unsigned int __at 0x2007 __CONFIG = _INTOSC_OSC_NOCLKOUT & //
> Internal
> > oscillator
> > _WDT_OFF & // No Watchdog
> > _LVP_OFF & // No Low-Volt
> > Program.
> > _DATA_CP_OFF & // No Code
> Protect
> > _PWRTE_ON;
> >
> > static unsigned char count;
> >
> > void main(void) {
> > CMCON |= 0x07; // Disable comparators. NEEDED FOR NORMAL PORTA
> > TRISB = 0x00; // Set port B as all outputs
> > TRISA = 0x00; // Set port A as all outputs
> > PORTA = 0xFF;
> > PORTB = 0xFF;
> >
> > while(1) {}
> > }
>
> --
> Richard.
> PGP Key-id: 0x5AB3D350
>
> Be careful of reading health books, you might die of a misprint.
> -- Mark Twain
>
>
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