Forums

PLL on LPC2000

Started by jdauchot February 2, 2009
come on you guys this is serious question

Regards

--- In l..., Timo wrote:
>
> jdauchot wrote:
> > OK how do I grandee this 1ms pulse not drifting
>
> You can't stop it drifting without external reference. Use ntp, radio
> time (en.wikipedia.org/wiki/Time_signal), gps, manual adjust... --
pick one.
>
> --
>
> Timo
>

An Engineer's Guide to the LPC2100 Series

On Mon, 2 Feb 2009, jdauchot wrote:

> come on you guys this is serious question

?!

You don't think these are serious answers?

-Kenny

--
Kenneth R. Crudup Sr. SW Engineer, Scott County Consulting, Los Angeles
O: 3630 S. Sepulveda Blvd. #138, L.A., CA 90034-6809 (888) 454-8181

jdauchot wrote:
> OK how do I grandee this 1ms pulse not drifting

To what accuracy?

Robert

http://www.aeolusdevelopment.com/

From the Divided by a Common Language File (Edited to protect the guilty)
ME - "I'd like to get Price and delivery for connector Part # XXXXX"
Dist./Rep - "$X.XX Lead time 37 days"
ME - "Anything we can do about lead time? 37 days seems a bit high."
Dist./Rep - "that is the lead time given because our stock is live....
we currently have stock."

Somtimes no, after reading some answers from previous e-mails

--- In l..., Kenneth Crudup wrote:
> On Mon, 2 Feb 2009, jdauchot wrote:
>
> > come on you guys this is serious question
>
> ?!
>
> You don't think these are serious answers?
>
> -Kenny
>
> --
> Kenneth R. Crudup Sr. SW Engineer, Scott County Consulting, Los
Angeles
> O: 3630 S. Sepulveda Blvd. #138, L.A., CA 90034-6809 (888) 454-
8181
>

I am not sure as I have no control over the receiving hardware and no
info on the way it work.

The only way I know it works its looking at a scope using the old CPU
8032 based hardware. Its a train of 8x 9 bit data packets starting
with a start bit (positive)on each data packet. It ends with a 20ms
gap. Each pulse has to be 1ms. Each bit of the remaining data packet
fires a relays on the receiving sub system(PIC Based). If the system
stop sending the data packets, the IO sub system will go into a fail
safe mode (drop all outputs). However. on the new hardware the IO
relays seem to fire randomly sugesting that the start bit is
expanding in some way due to drift of the PLL

Regards

Jean-Jacques

--- In l..., Robert Adsett
wrote:
>
> jdauchot wrote:
> > OK how do I grandee this 1ms pulse not drifting
>
> To what accuracy?
>
> Robert
>
> http://www.aeolusdevelopment.com/
>
> From the Divided by a Common Language File (Edited to protect the
guilty)
> ME - "I'd like to get Price and delivery for connector Part # XXXXX"
> Dist./Rep - "$X.XX Lead time 37 days"
> ME - "Anything we can do about lead time? 37 days seems a bit
high."
> Dist./Rep - "that is the lead time given because our stock is
live....
> we currently have stock."
>

On Tuesday 03 February 2009 02:22, Kenneth Crudup wrote:
> On Mon, 2 Feb 2009, jdauchot wrote:
> > OK how do I grandee this 1ms pulse not drifting
>
> You can't, really (temperature control, maybe?), but what I/we're
> saying is it shouldn't matter for your application; I'm pretty sure
> that at 1KHz measureable drift won't really be a factor, esp. in a
> UART-style application.

What is more likely is drift in the legacy system causing a problem.
Really old systems had crystals in a small oven (a
resistor -thermistor - transistor combo) to stabilise the temp.
Failure of this oven caused all sorts of wierdo problems.

--
Rgds
JTD

On Tuesday 03 February 2009 09:59, jdauchot wrote:
> I am not sure as I have no control over the receiving hardware and
> no info on the way it work.
>
> The only way I know it works its looking at a scope using the old
> CPU 8032 based hardware. Its a train of 8x 9 bit data packets
> starting with a start bit (positive)on each data packet. It ends
> with a 20ms gap. Each pulse has to be 1ms. Each bit of the
> remaining data packet fires a relays on the receiving sub
> system(PIC Based). If the system stop sending the data packets, the
> IO sub system will go into a fail safe mode (drop all outputs).
> However. on the new hardware the IO relays seem to fire randomly
> sugesting that the start bit is expanding in some way due to drift
> of the PLL

I would think it's more to do with rise times than drift.

--
Rgds
JTD

jdauchot schrieb:
> come on you guys this is serious question

Did you look into your crystals specs ? It should tell you about the drift.
Now do the math and compare it with the 1ms period. I am pretty sure a
drift in the PPM range will not hurt.

But it seems you are seeking for a global answer, which can't be given
by the information you did provide (and maybe even not, if you would
have done so).

--
42Bastian

Note: SPAM-only account, direct mail to bs42@...

Thanks for all the responses

I am using the IAR LPC2148 Kickstart demo board and I am driving the
IO sub system by pulsing P1.25 via a timer0 1ms interrupt. The P1
port is configured in GPIO. I will try using FGPIO, would that
improve the rise time. I am not a hardware engineer

Regards

Jean-Jacques
--- In l..., jtd wrote:
>
> On Tuesday 03 February 2009 09:59, jdauchot wrote:
> > I am not sure as I have no control over the receiving hardware and
> > no info on the way it work.
> >
> > The only way I know it works its looking at a scope using the old
> > CPU 8032 based hardware. Its a train of 8x 9 bit data packets
> > starting with a start bit (positive)on each data packet. It ends
> > with a 20ms gap. Each pulse has to be 1ms. Each bit of the
> > remaining data packet fires a relays on the receiving sub
> > system(PIC Based). If the system stop sending the data packets,
the
> > IO sub system will go into a fail safe mode (drop all outputs).
> > However. on the new hardware the IO relays seem to fire randomly
> > sugesting that the start bit is expanding in some way due to drift
> > of the PLL
>
> I would think it's more to do with rise times than drift.
>
> --
> Rgds
> JTD
>

jdauchot schrieb:
> Thanks for all the responses
>
> I am using the IAR LPC2148 Kickstart demo board and I am driving the
> IO sub system by pulsing P1.25 via a timer0 1ms interrupt. The P1
> port is configured in GPIO. I will try using FGPIO, would that
> improve the rise time. I am not a hardware engineer

Did you "play" with the period ? I mean, did you try it with 900us or
1100us ?
It'll give you a feeling if you have to be concerned about the drift.

--
42Bastian

Note: SPAM-only account, direct mail to bs42@...