Computer Display?

[HenrikOlsson]

Hi Ed,
If there really ARE pulses with a frequency of 2.4MHz then I'd say that's a problem, note that the width of the pulses alone doesn't say anything about the frequency. Can you post a screenshot and tell us exactly where you're probing?

[Ramius]

Hi henrik!
No idea what is going on I swear the analyzer showed 2.4mhz for the narrow pulse width and now when I go to do a screen shot it is much lower! Probably I was looking at the pulses before adding all the decoupling caps?

[Ramius]

Hi Henrik and all!
Just an update. After rebooting my computer things settled down and became more reasonable. I did some intense research and it turns out the TXB0104 does not like a capacitance load on any of the output or input pins of more than 70nf! So while twisting the wires seemed like a good idea (suspecting noise) it just made everything worse! I cannot believe they would make a device with such limits! Also I got my 3.0v regulator and things again look good. Thanks. Best, Ed

[Charlie]

1) There is no way you are getting more than 70 nF capacitance from twisting a few inches of wire. Not even 70 pF. 70 nF is HUGE!
2) All signal pins on all devices will have some value of capacitance that renders them inoperable. The value at which things fall over is usually related to the signalling speed, and sometimes related to the driver design.
3) Power pins are not signal pins. They need capacitors.
4) If rebooting your computer addressed the problem, then your circuit was fine all along. But it's hard to see how it could have had any impact at all. Very unusual. I think there's still "some 'splaining to do"...

[Ramius]

Hi Charlie!
You are right and I started off trying to go a few feet. At a few feet from the output of the TXB0104 to the PIC things would go "spritual". Then at a shorter distance back to "normal". You are also right there is something very strange and wierd going on just not sure what it is or how to track it down. Best, Ed

[Demon]

Do you have VERY large speakers near your desk? Or possibly industrial power cables?

(just a silly idea)

Robert

[Ramius]

Hi Robert!
Not silly, great idea and no, no big speakers as I also worked with a digital compass and try to stay with only brass for everything including the pressure sensor. Once in a great while aluminum which is difficult to solder! Yes, there is aluminum solder and it takes a lot of heat. Typically I take the aluminum soldering rods and cut them down so they are thinner than what I am trying to solder. While the specs for the TXB0104 states it can handle upto a 70nf (.07mf) load there is some other factor. Another problem was with my code. I had a "gosub" that should have been a "goto" which fixed a lot of issues. I have not tried longer cable lenght(s) again, just working with short lenghts.

What I would really love to know is what code to use and what the code would look like so I can run the PIC at full speed and not delayed using ICD to see the parameters. Maybe assign some pins to feed a MAX232 and use hyperterminal or similar? Second, I know this is probably been asked a million times and is there a simple way to tell at what speed the code is really running?

So many questions, so little time!

Best to all, Ed