RS232 filter IC

[MC]

Heywood Jablome wrote:

Hi all,

I'm trying to send RF signals from a PC to a microprocessor. I have a
microprocessor which is programmed to receive serial in at 1200 baud. It
does what its told to when it is directly connected to the computer, but is
very temperemental when connected to the RF link. I believe that the RF link
is not outputting clean 0's and 1's, and therefore is tricking the
microprocessor. I would say that the microprocessor is sensing a rising edge
or a falling edge and using that to calibrate the baud rate for the next
bit. Problem is (i think) that each bit received by the receiver is not a
clean 1 or a clean 0, and is therefore being misinterpreted by the
microprocessor.


I have purchased the RX434LC and the TX434 from
http://www.oatleyelectronics.com/remote.html

I finally had a look on Oatley, and the RX434LC is
*not* crystal locked (whereas the RX434 is crystal driven)

So., your problem *could* be due to a (small/variable) difference
in the oscillator frequencies of the receiver and transmitter.

 

[Jeff]

On Fri, 12 Nov 2004 12:08:05 +1100, "Heywood Jablome" <reply to
thread> wrote:

Hi all,

I'm trying to send RF signals from a PC to a microprocessor. I have a
microprocessor which is programmed to receive serial in at 1200 baud. It
does what its told to when it is directly connected to the computer, but is
very temperemental when connected to the RF link. I believe that the RF link
is not outputting clean 0's and 1's, and therefore is tricking the
microprocessor. I would say that the microprocessor is sensing a rising edge
or a falling edge and using that to calibrate the baud rate for the next
bit. Problem is (i think) that each bit received by the receiver is not a
clean 1 or a clean 0, and is therefore being misinterpreted by the
microprocessor.

Most radio receivers need some preamble bits, I would not expect
intermittent data (say typed from a terminal) to transfer correctly.
I've always used a packet protocol (and preamble) with radio links.

Regards,
Jeff

 

[Franc Zabkar]

On Sat, 13 Nov 2004 16:33:04 +1100, "Heywood Jablome" <reply to
thread> put finger to keyboard and composed:

Check whether the output of the receiver is open collector, ie does it
go to 5V in the absence of a load? If it is OC, then you may need a
pull-up resistor.



I put in a pull down resistor in and it didn't help. It is receiving
something (I have an LED connected to the output) so it isn't open
collector.

It looks like you're not the only one having problems with the Oatley
kit:
http://www.rev-ed.co.uk/picaxe/forum/topic.asp?topic_id=1730&forum_id=12&Topic_Title=Picaxe+Wireless+Problems+via+RX434+and+TX434&forum_title=No+new+posts+please%21+6&M=True&S=True


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.