Searching \ for '[PIC] [EE] Problems with NOPPP and PIC16F84A' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/devices.htm?key=16F
Search entire site for: '[EE] Problems with NOPPP and PIC16F84A'.

Exact match. Not showing close matches.
PICList Thread
'[PIC] [EE] Problems with NOPPP and PIC16F84A'
2007\03\02@161042 by Joseph Marlin

picon face



Byron A Jeff wrote:
>
> What voltage does the serial port generate? All of the serial port designs
> were designed to work with true blue EIA-232C serial ports. PCs haven't
> had
> such serial ports in close to 10 years. Many PC serial ports only generate
> voltages of 0 to 5V, with some generating voltages as low as 3.3V.
>

 I'm not using the serial port. The NOPPP design interfaces to the parallel
port. Not that that really matters.


Byron A Jeff wrote:
{Quote hidden}

My circuit uses and external pc power supply to send 12v to !MCLR,
controlled by the parallel port via a transistor, and the 5v for the chip's
voltage input. I thought I had read that the '84A needed about 12v on !MCLR,
but perhaps I was mistaken and I need something more powerful.
 
  When you say Vpp, are you actually referring to !MCLR? Because every
programmer design I've ever seen applies 5v to Vpp to power the chip and
uses the higher voltage purely to trigger the chip into high-voltage
programming mode on !MCLR. Perhaps I'm misunderstanding something, but
perhaps not. I'll attempt applying a higher voltage to !MCLR when I get back
to it, but I do believe I already tried with a wall-wart outputting about
17v and the results were the same, however I may have just tried this with
the COM84. I can't remember. I'll verify this when I get back to the
project.

--
View this message in context: www.nabble.com/-PIC--Problems-with-NOPPP-and-PIC16F84A-tf3330790.html#a9277465
Sent from the PIC - [PIC] mailing list archive at Nabble.com.

2007\03\03@011500 by Byron A Jeff

face picon face
On Fri, Mar 02, 2007 at 01:10:40PM -0800, Joseph Marlin wrote:
> Byron A Jeff wrote:

> > What voltage does the serial port generate? All of the serial port designs
> > were designed to work with true blue EIA-232C serial ports. PCs haven't
> > had
> > such serial ports in close to 10 years. Many PC serial ports only generate
> > voltages of 0 to 5V, with some generating voltages as low as 3.3V.

>   I'm not using the serial port. The NOPPP design interfaces to the parallel
> port. Not that that really matters.

Actually it does. Sorry for the mistake.

Michael covers two of the major issues using the parallel port: port voltage
and cable crosstalk. For cable crosstalk In his README he suggest using a
cable of 3 ft or less.  I agree. Even when you get a statically correct
reading on the programmer, when the bits start flying, it can get messed up.

The second is port voltage. The NOPPP was designed at a time where parallel
ports actually output 5V for a high signal. Virtually no parallel port does
that today. Most output 3.3V max which isn't enough to trigger a high reading
on the PIC. The revised schematic in noppp-x.gif addresses the issue by using
pullups with diodes.

One other thing I see is that for that schematic Michael has a 2.2K pullup
between the 13V power supply and MCLR. That only provides 5 mA of current
which is 10 times less than needed. Substitute a 220 ohm resistor there
instead.

{Quote hidden}

12V is the bare minimum. 13V is nominal.

>    When you say Vpp, are you actually referring to !MCLR?

I'm referring to the 13V programming voltage that must be applied to the MCLR
pin. The programming voltage isn't a reset signal, which MCLR (Master Clear)
indicates. It's really two different functions (reset and programming) assigned
to a single pin.

> Because every
> programmer design I've ever seen applies 5v to Vpp

That's Vdd, not Vpp.

> to power the chip and
> uses the higher voltage purely to trigger the chip into high-voltage
> programming mode on !MCLR.

That's Vpp.

> Perhaps I'm misunderstanding something, but
> perhaps not. I'll attempt applying a higher voltage to !MCLR when I get back
> to it,

13V. No more than 14V or you'll potentially fry the part.

> but I do believe I already tried with a wall-wart outputting about
> 17v and the results were the same, however I may have just tried this with
> the COM84. I can't remember. I'll verify this when I get back to the
> project.

Keep at it. Also I would seriously advise you to heed my advise about using
an updated part. The 16F84A limitations will lead to poor design habits out
of necessity.

BAJ

2007\03\03@154219 by Joseph Marlin

picon face

>One other thing I see is that for that schematic Michael has a 2.2K pullup
>between the 13V power supply and MCLR. That only provides 5 mA of current
>which is 10 times less than needed. Substitute a 220 ohm resistor there
>instead.

This could very well be the thing that's giving me problems. I'll go back
through and check all of my amperages to see what kinds of values I'm
getting and try replacing that resistor. I appologize for all of my
stupidity on this subject because I have almost no real experience in
working with electronics, but I do so enjoy jumping into the deep end, which
I realize doesn't really constitute a right for me to ask someone else to
pull me out, so thank you once again for your patience and helpfulness. I'll
try and pass it on.

{Quote hidden}

*slap to the forehead* d'oh! I'm really sorry, I knew that. Don't know what
I was thinking. My appologies.

So yes, once I can find another 9v for my multimeter I'll address these
issues and, if I'm going to report anything, I won't report until I can
report sucess. Thank you again and, again, my appologies for inconviniencing
you with my noobish ways.

--
View this message in context: www.nabble.com/-PIC--Problems-with-NOPPP-and-PIC16F84A-tf3330790.html#a9289482
Sent from the PIC - [PIC] mailing list archive at Nabble.com.

2007\03\03@173259 by Bob Axtell

face picon face
Joseph Marlin wrote:
{Quote hidden}

No apology is ever needed here.

--Bob

2007\03\03@200251 by Byron A Jeff

face picon face
On Sat, Mar 03, 2007 at 12:42:18PM -0800, Joseph Marlin wrote:
>
> >One other thing I see is that for that schematic Michael has a 2.2K pullup
> >between the 13V power supply and MCLR. That only provides 5 mA of current
> >which is 10 times less than needed. Substitute a 220 ohm resistor there
> >instead.
>
> This could very well be the thing that's giving me problems. I'll go back
> through and check all of my amperages to see what kinds of values I'm
> getting and try replacing that resistor. I appologize for all of my
> stupidity on this subject because I have almost no real experience in
> working with electronics,

There's no stupidity here. That would be insisting that you did everything
right so it's Microchip's fault or something like that.

The only part if you education I'll keep pounding on is upgrading to a newer
part. In the 16F family I'd suggest the top end parts with the nanowatt
features and the most memory which is the 16F88 for the 18 pin package and
the 16F886/16F887 for the 28/40 pin packages. It'll help you a lot in the
long run.

> but I do so enjoy jumping into the deep end, which
> I realize doesn't really constitute a right for me to ask someone else to
> pull me out, so thank you once again for your patience and helpfulness. I'll
> try and pass it on.

No problem. Hope that it works for you.

{Quote hidden}

Again no need to apologize. Just clearing up a misunderstanding.

> So yes, once I can find another 9v for my multimeter I'll address these
> issues and, if I'm going to report anything, I won't report until I can
> report sucess. Thank you again and, again, my appologies for inconviniencing
> you with my noobish ways.

Actually report even if it's not successful. Homebrew programmer debugging
tends to be an interative process.

BAJ

More... (looser matching)
- Last day of these posts
- In 2007 , 2008 only
- Today
- New search...