mrburnette
Senior Member
Morse Code Decoding @10WPM with a PICAXE 08M2
See the 20X2 in action: http://www.youtube.com/watch?v=9kZOqdeUl2w&feature=youtube_gdata
2011 Aug 26: Updated code base to sync with 20X2 code. Eliminated GOTO and optimized algorithm. These changes reduced the code size while increasing the performance from 8WPM to 10WPM based on ARRL training files. With the 20X2, speeds of 15WPM+ can be achieved (29WPM/15Farnsworth.) You can feed the NPN-clipper circuit with the output of a 700Hz-800Hz Morse oscillator (NE555, etc.) attached to a key for instant visual feedback while learning Morse Code.
http://www.picaxeforum.co.uk/showthread.php?19088-Morse-Code-Decoder-for-Cheap-using-a-20X2&p=177912#post177912
The 08M2 running at 32MHz and using the Pulsin command can decode 10WPM Morse Code in a similar manner to the 20X2. However, since the 20X2 using Pulsin at 64MHz "times out" much quicker and the WPM that can be handled is much higher... the 20X2 works without modification of code for 5WPM to 15WPM (higher if Farnsworth spacing is being used.)
However, error free decoding of 10WPM on a 08M2 is kind of a fun project. The Morse signal is taken from the Wikipedia article on Morse Code and the 8WPM is the alphabet, A-Z. A single transistor NPN transistor is utilized for clipping the audio output from your PC... a value of 0.75V - 0.8V is required to saturate the NPN and adequately clip the waveform so that Pulsin can decode the signal. My previous article on Morse using the 20X2 has the SPICE definition of the NPN circuit, so I will not repeat here. If you wish to do anything more seriously than just play around, you will need to build a much better amplifier and clipping circuit. Input from the NPN collector goes to the 08m2 pin C.3 and you can tie a LED to C.2 through a 100-150 ohm resistor to +5V.
Basic NPN clipper: (see 20X2 thread for JPG of circuit)
+5V through 10K to Collector of NPN
Collector goes to pin C.3 of PICAXE 08M2
GND goes to Emitter of NPN
GND goes to shield of earphone jack on PC
Base goes through 2.2K resistor to earphone jack center
As with the 20X2 code, I'm using my Magic Morse DAH-Weighted algorithm. A PDF can be found in the 20X2 article that explains the scheme.
- Ray
See the 20X2 in action: http://www.youtube.com/watch?v=9kZOqdeUl2w&feature=youtube_gdata
2011 Aug 26: Updated code base to sync with 20X2 code. Eliminated GOTO and optimized algorithm. These changes reduced the code size while increasing the performance from 8WPM to 10WPM based on ARRL training files. With the 20X2, speeds of 15WPM+ can be achieved (29WPM/15Farnsworth.) You can feed the NPN-clipper circuit with the output of a 700Hz-800Hz Morse oscillator (NE555, etc.) attached to a key for instant visual feedback while learning Morse Code.
http://www.picaxeforum.co.uk/showthread.php?19088-Morse-Code-Decoder-for-Cheap-using-a-20X2&p=177912#post177912
The 08M2 running at 32MHz and using the Pulsin command can decode 10WPM Morse Code in a similar manner to the 20X2. However, since the 20X2 using Pulsin at 64MHz "times out" much quicker and the WPM that can be handled is much higher... the 20X2 works without modification of code for 5WPM to 15WPM (higher if Farnsworth spacing is being used.)
However, error free decoding of 10WPM on a 08M2 is kind of a fun project. The Morse signal is taken from the Wikipedia article on Morse Code and the 8WPM is the alphabet, A-Z. A single transistor NPN transistor is utilized for clipping the audio output from your PC... a value of 0.75V - 0.8V is required to saturate the NPN and adequately clip the waveform so that Pulsin can decode the signal. My previous article on Morse using the 20X2 has the SPICE definition of the NPN circuit, so I will not repeat here. If you wish to do anything more seriously than just play around, you will need to build a much better amplifier and clipping circuit. Input from the NPN collector goes to the 08m2 pin C.3 and you can tie a LED to C.2 through a 100-150 ohm resistor to +5V.
Basic NPN clipper: (see 20X2 thread for JPG of circuit)
+5V through 10K to Collector of NPN
Collector goes to pin C.3 of PICAXE 08M2
GND goes to Emitter of NPN
GND goes to shield of earphone jack on PC
Base goes through 2.2K resistor to earphone jack center
As with the 20X2 code, I'm using my Magic Morse DAH-Weighted algorithm. A PDF can be found in the 20X2 article that explains the scheme.
- Ray
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