Ok, here are the results.


First, I tested just the parport with the PSU disconnected. I am using the Computer PSU as I mentioned. With it disconnected, each pin registered a high of about 4.4V and a low of 90 mV. Connecting the PSU, but having it off resulting in wierd readings (a high would be 2.2V for example).. but I considered this insignificant since I would be only operating with the PSU on. With it on, I achieved the same results on the parport pins 2 through 5 - High = 4.4V and low = 90 mV.
Now, the voltage directly across the PSU's pins was 5.2V. +Vcc on the HCT (and yes, it is a 74HCT573 exactly) was 5.2V, along with +Vdd on the Pic. Also, pin 11 on the HCT was +5.2V (LE). GND on both the HCT and PIC were 0mV, and same with Pin 1 on the HCT (OE). Now, I tried the voltages at the PIC pins (first I tried with just the parport remember). I did this with the PIC removedl. For each pin (RB6/7, MCLR and PGM), a high was 5.2V and a low anywhere from 0.2 - 1.6 mV. The Q4/Pin 10 on the parport test showed a 5.2V high and a 32 mV reading. And the READ pin did follow RB7 correctly when using Debug.

I am using RB4, not RB3 as I am supposed to. So out of all of this, it seems the potential problem is the high of 5.2V instead of 5 as you suggested. Maybe this isn't a problem, but this is hte only thing I can see. I also switched PICs, again, and still didnt work. I think that ISO idea would be a great thing (not only for me), since it would enable live testing. I am so stumped. You should develop some FreeBSD code :-) I have only used their ppi interface so far... pretty easy.

Anyway, maybe all my testing might tip you off. Let me know.

Oh, btw, I am using a pot for the 1k resistor since I dont have a 1k on hand... and making a combo out of others is too annoying at this point. I have verified 1k on the pot though.

Thank you,

Jai
On Sat, Aug 24, 2002 at 04:24:31PM -0400, Byron A Jeff wrote:
> 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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