Detrick Merz wrote:
> On 10/29/07, Byron Jeff <byronjeff@clayton.edu> wrote:
>   
>>> Thoughts?
>>>       
>> Only two. Did you program the chip? Did it work?
>>     
>
> A minor breakthrough today.  I took all the unused inputs on the
> 74HCT573 and tied them to ground.  Using FPP again, and a very simple
> bit of code compiled for an 'F84A, I was able to successfully do the
> following:
>
> - read the PIC (returned "blank" or all 0's every time I did it)
> - program the simple code to the PIC
> - verify the PIC
> - restart FPP
> - read the PIC again, noting that what was read matched my original code
>
> This worked on 2 different 'F84A's, one of which I had programmed
> years ago (it actually returned the old code the first time I read
> it), and one which was brand new.
>
> I tried the same with an 'F628A using 'F628A code, but no love there.
> At least I know the programmer works now.  Maybe the 'F628A is dead,
> or maybe it doesn't like the 16.3v I was putting into MCLR (or maybe
> it's dead because I was putting 16.3v into MCLR).
>
> For the "what cable works" file, this was done using a ~5' Belkin
> parallel cable.  I haven't gotten around to making a Cat5 based one
> yet, but was anxious to try a test after grounding inputs on the
> latch.  FPP was set to us the following timings (I haven't tried any
> lower, as my time is cheap, so a few extra seconds of programming time
> won't bother me):
>
> Prog cycle delay: 50ms
> Power up delay: 100ms
> I/O delay: 50 ticks
>
> I think I've got a 7808 around here I might try to wire in against my
> 7805, to get MCLR down to a more appropriate level, and try the 'F628A
> again.  If it is fried, I have a couple other PICs a bit higher up in
> the line I could try to write something simple to, just to try.
>
> So, what *really* made things work this morning?  I ordered a PicKit2
> direct from Microchip last night.  I'm sure that scared something into
> place!
>
> To answer the next question, "why use FPP instead of WinPicProg,"
> well, I tried WPP too.. while it was working fine the other day, today
> it doesn't seem to want to find my parallel port.  Go figure.
>   
16V is a bit high for a PIC. Can't you clip it with a zener and a 
current limit resistor to 13V?
The F628A has a different algorithm from the F84A.

For cheap programmers, I like DIY Electronics K128 (socketed parts) or 
K182 (ICSP parts)
as they work very well, cost $60 USD. My clients own bunches of these, 
and none have ever
failed them. They use USB<>serial FTDI devices, and need no other power 
supply except for
the 5V from the USB port. It uses a voltage tripler to obtain 15V then 3 
diode drops to reach
13V.

--Bob A
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