If you want to catch the transition from 1-0 or 0-1
accurately on the receiver, you will have to over sample the incomming
data. ie sample 4, 8 or even 16 time the transmit rate. Doing
that you will be able to work out where the clock edge of the trasnmitter is and
adjust the receiver accordingly.
Chad
Jim,
what i am doing in codifing 1 byte as manchester (1-0 or 0-1) and
then sending it over the uart ,so it is actually working as an uart, thas
why it seems not to work. I've understood it now. I'll use software
manchester
Regards
Javier
I'm a little confused. You said,
earlier, I think, that you
are using manchester coding. That really does not
fit with
"UART". Trying to use a UART with manchester seems like a
real
problem. I'd do it all in software.
Jim
On Tue, 22 Mar 2005
13:39:40 -0300
"Javier Fiasche" wrote:
>
That's right the uart ist triggering on noise.
> Unfortunatelly my
reciever does not have signal strength
> output. I am using
> a very
cheap
> Yong Horng reciver and transmitter (not a transciver).
>; I
would need to detect a real transmition and to reject
> noise, but
>
digitally, ideas???
> I tried transmitting a Hi level before setting the
uart
> to transmitt, and
> trying to detect this continuos hi level
on the reciver
> before setting the
> reciever uart to recive, But
it doesn't work that
> fine............
> Thanks
>
Javier
>
> -----Mensaje original-----
> De: Bruce Parham
[mailto:obparham@jpl.nasa.gov]
> Enviado el: Martes, 22 de Marzo de 2005
01:29 p.m.
> Para: AVR-Chat@yahoogroups.com
> Asunto: Re: [AVR-Chat]
RF link
>
>
>
>
> Javier Fiasche
wrote:
> >
> > Hi everybody, i'm having trouble.....
>
>
> > I am trying to transmit data over Rf using 2
>
atmega8l(via USARt) and
> 433Mhz
> > transmitter and reciver
module. One will work as
> transmiter and the other
> as
>;
> reciever. The transmiter will send a code composed of:
>
>
-----------------------------
>
> | SYNC
|Package|CHECKSUM|end|
> >
-----------------------------
> > all of this coded as manchester. Afer
sending the
> package, the mega8 will
> > shut down the
transmitter until next transmition.
> > The reciever would listen to
the reciver module only
> when it is desired,
> > selecting this
with a pushbutton.When i dont want to
> listen, i shut down
>
the
> > 433 reciver module
> > Here is the problem:
>
> i dont seem to sincronice
the transmitter and
> the reciver usart,
> because
> > when
the transmitter is off and the reciever is on i
> keep getting and
>
> Framming error.
> > i've tried
listening to the RXd pin, with the
> RXEN=0, till i get a
> >
long enought "1" and then set the RXEN=1, but this seem
> to have
no
> > effect.........
> > Any ideas of how to sincronice
them????????????
> >
> > Thanks
> > Javier
>
> Sounds like the rx doesn't have any squelch and the uart
> is
triggering on
> noise.
> I don't know what kind of receiver you're
using but, if
> it has a RSS (Rx Sig
> Strength)
> line, you
could use that to enable/disable the rx uart.
> (You may need to
use
> the
> analog comparator on the RSS signal.)
>
>
Bruce
>
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