gbbickerton
Member
Manchester encoding
Quite some time ago I posted a simple manchester encoding and decoding program and Hippy kindly showed how it could be done more easily. However I do not think that most people realise that the manchester encoding is needed for the receiver modules to work correctly they use what they call bit slicing, this uses the average value of the receiver output as the switching level for a comparator to determine what is a 1 and what is a 0 on one of my receivers this level has a such a short time period that it would not be able to receive 8 0 bits or 8 1 bits at 2400 baud without error. This means that you must send a peamble of equal 1's and 0's to get the comparator level in the receiver set up before any data and then use manchester encoding to keep the receiver operating at the correct level for the data I have found that I can double the reliable range of my system using this method. This also means that slow serial links would not work either.Has any one looked at AFSK as used by radio teletype the chips may not be available but the tones should be possible in software although decoding them will probably need hardware.
Quite some time ago I posted a simple manchester encoding and decoding program and Hippy kindly showed how it could be done more easily. However I do not think that most people realise that the manchester encoding is needed for the receiver modules to work correctly they use what they call bit slicing, this uses the average value of the receiver output as the switching level for a comparator to determine what is a 1 and what is a 0 on one of my receivers this level has a such a short time period that it would not be able to receive 8 0 bits or 8 1 bits at 2400 baud without error. This means that you must send a peamble of equal 1's and 0's to get the comparator level in the receiver set up before any data and then use manchester encoding to keep the receiver operating at the correct level for the data I have found that I can double the reliable range of my system using this method. This also means that slow serial links would not work either.Has any one looked at AFSK as used by radio teletype the chips may not be available but the tones should be possible in software although decoding them will probably need hardware.