Save reading, load reading, small bitcount calculator

[holiman]

#./rfidler.py /dev/RFIDler 'set tag askraw' 'potset h 150' 'set fc 745' 'set rate 33' dump 6000
sending 'SET TAG ASKRAW'
sending 'POTSET H 150'
sending 'SET FC 745'
sending 'SET RATE 33'
Wrote dump to dump_20141121-075357.xml

• Added functionality to plot from a previously saved reading:

  ./rfidler.py /dev/RFIDler load dump_20141121-075357.xml

• Added some logic to print out bit periods, i.e. the number of samples before the next toggling (not the true bit period, just to help determine the true bit period)

[AdamLaurie]

Thanks for this - looks useful, but you can't use the command "DUMP" as it conflicts with an existing command in RFIDler itself. I would suggest "STORE". Also, I would prefer it if the command allowed filename prefix. The auto adding of time/datestamp is good, but you need to be able to specify the path and base filename.

[holiman]

I've fixed that now, and also fixed a bug where the three first ANALOGUE values were overwriten. I also started an autocorrelation graph, but that is commented out, since I haven't gotten it to work quite as it should.

[holiman]

Oh, and on another note.. I don't quite see how the 'scale' - factor in analogue.c was supposed to work. Does it do what you intended it to do ? It looks like you had in mind to make 'scale' a float, but in order for that to function properly, you'd probably be better off implementing a sample interpolator also. Right now, the receiver happily plots 9000 points, but only 4500 will be filled with data.

[AdamLaurie]

Scale is basically using a fixed size array to store data, so simply discards samples as appropriate. It would be better to average them somehow, but I was worried about this affecting the real-time nature of the data collection.