On Fri, 12 Sep 2003 12:54:39 -0400, you wrote:

>> Bob Ammerman wrote:
>>
>> > The user is depending on  the receiver recognizing the start bit
>correctly,
>> > which is problematic at best.
>>
>> Why ?
>> He is using the UART as an async UART, and hence uses normal,
>> standard start/stop bits. It's of no importance that the
>> higher level software then decodes the "bytes" as Manchster code...
>
>Because he really doesn't have a good idea of where the start of the =
message
>is. Typically the receiver will either be generating noise on its =
digital
>output, or possibly squelch will keep it quiet. In either case, the UART=
 can
>easily see the wrong bit as the start of things (it can't tell a real =
start
>bit from a data bit).

I think there may be some confusion arisin here - I was under the =
impression that the issue was
generating RF -suitable data patterns from TX uart.=20
I don't think anyone was proposing trying to receive it via a uart - if =
so, it's really not a good
idea.=20
What you typically see is noise, then the preamble, which stabilises the =
gain and the data slicer,
then you need some synchronisation pattern or gap to define the byte =
framing.=20
A bit-bashed receiver (or interrupt driven, or using input capture =
hardware) which can deal with all
the rubbish correctly is not hard to implement and will be much more =
reliable than trying to bend a
UART into doing something it's not deaigned for.

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