AVR-Chat

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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