On Thu, Aug 21, 2003 at 07:56:34AM -0400, Jai Dhar wrote:
> Hello all,
>
>Despite all the things I have tried in the last few months, I STILL
>have not got a successful program loaded into my 16f628.

Oh dear!

> I am using TLVP with
>David Tait's FPP. I HAVE verified that the parport works by using FPP's debug
>function, and every pin works out as it should. I have rewired numerous times
>from scratch to ensure no errors.

If you've verified pin operation at the socket and it's right, then no amount
of rewiring will matter.

> Initially, I had a longer parport cord
>(6'), but I made my own that was much shorter.

Good.

> I thought maybe this was the
>problem, but it works with the debug feature.. I verified each pin's voltage
>high

What voltage? It needs to be between 4 and 5 volts.

> and low

Same here. It needs to be between 0 and 1 volts.

> with a DMM while switching them with FPP's debug feature. Even
>the read pin works fine, as it shows in the debug section.

That's good.

> I have increased
>the cycle delays to mad numbers that are extremely high, and still nothing
>works.

Cycle delays won't help if the problem is elsewhere.

> It just sais Read: 3FFF expected: 2828 (as 2828 was the first code to
>program). What is going on? I am getting desparate here for nothing has
>worked. I have even switched PIC's.

Jai,

It's not supposed to be this hard. I'm so sorry that you are having all these
troubles. Maybe we can setup a chat somewhere so that you and I can go over
this together.

I'm going with the only one presumption:

* That you are using a parallel cable of 2 feet or less.

Let's go through it one more time:

* Are you sure that the PIC has 5V power? And it's grounded?
* Are you using a 74HCT573? The HCT is critical for level conversion.
* Are you sure that the HCT573 has power and its control signals are wired
  correctly. Power needs to be 5V. BTW where are you getting that from?
* You have RB4 pin 10 wired as the PGM pin right? Not RB3.
* You verified each signal pin (RB7/DATA, RB6/CLK, RB4/PGM, MCLR) to make sure
  that they toggle between 0-1V for low and 4-5V for high?
* You double checked the polarity of each of the control signals?
* You double checked that the READ IN pin follows the DATA OUT pin.
* You have the resistor in place between Q0 (pin 19) of the HCT573 and RB7/DATA
  of the PIC?
* Have you checked the voltage between Q4 (pin 15) of the HCT573 and pin 10
  of the parallel port to ensure that it's between 0-0.8V for low and above
  2.0V for high?

Note that the voltages are critical because if they are not above the required
thresholds, then you won't get the desired effect.

I think I'm going to start working on a TLVP debugging floppy/iso using
picprg2.3e. One thing I think that both FPP and picprg are missing is the
ability to sigle step through the programming process. Because then I would
suggest verifying each step during a live programming session so that you can
see using the DVM what's actually going on.

Don't rewire again. Changing for change's sake isn't going to help. Take one
more crack at configuring FPP while I try to get a simple floppy/iso image
together that can facilitate debugging the programmer.

We will get this thing working. We must!

Again I am deeply sorry at your frustration. I will do my best to help you get
it working.

BAJ

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