On Thu, Jan 19, 2017 at 6:59 PM, IVP wrote: > Hi Matthew, > > There are two important points about using those little 433MHz links > > When the receiver is not receiving a bona fide signal its AGC is turned > right up for signal detection and that's what causes the random digital > noise on the output > > Transmitting data to the receiver is best done using Manchester coding, > which is a balanced signal and also self-clocking > > https://en.wikipedia.org/wiki/Manchester_code > > Recovered data bit rate is half the baud rate because of the 01 and 10 > representations > > Sending "normal" bytes of data can cause the receiver's output to lurch > all over the place because of the probable unbalanced DC, eg a string > of 0s or 1s that will likely be found in data bytes > > A reliable link is established initially by sending a pre-amble of someth= ing > like a couple of bytes of 01010101, which turns the AGC down, lets the > receiver settle and allows the decoder to determine the baud rate by edge > detection or bit length measurement, followed by data, which might includ= e > an ID byte or bytes to identify the transmitter, as you would on an I2C b= uss > > Until you've established a verified link just ignore the output noise > > Joe > > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2016.0.7998 / Virus Database: 4749/13800 - Release Date: 01/19/1= 7 > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .