In principle, if I had to decode Morse code without a MCU, Perhaps the simplest circuit for distinguishing "long" vs "short" pulses uses a Camenzind 555 timer ICs in something like a "missing pulse detect" circuit. Is there a good circuit that can detect when a signal goes high for a certain amount of time? You might find some of the articles in early issues of Byte Magazine at the library. Which the decoding algorithm, doing its best with slightly uneven element spacing and a result string that didn't match any known Morse character, got one of the above digraphs. Operators naturally developed keying habits on common words, and would key (and understand) f/ex, the word 'the', Your hardware decoder would need to be similarly adaptive.Īs an aside, an interesting issue came up when the words 'T5' or '6E' appeared frequently in the decoded text. The same technique was applied to decoding hand-sent Morse off the air, with a simple circuit going high and low with the receiver's audio output, fed to a similar algorithm. The solution ended up being for the decoder program to initially collect enough white-black to black-white transition times to discover the mean wide-bar and narrow-bar times, assign '1's and '0's, respectively, to the collected data, and continue decoding the incoming stream while simultaneously updating the wide-bar and narrow-bar mean times to account for changes in the wand speed over the bars. It was assumed impractical (until shown otherwise) due one's inability to hand-scan at a uniform speed. The reader (person, not machine) could then scan it into their machine with a hand-held scanner. There were some hobbyist experiments (in the early '80s, I believe) with decoding variable speed digital data with the intent of being able to distribute code to accompany magazine articles by printing it as bar-codes.
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