Logic level parsing Rigol oscilloscope CSV data with F#

I was recently debugging a SPI communication but had no logic analyser. Fortunately my oscilloscope (rigol DS1052e) can export a capture as CSV (I assume that most digital oscilloscopes can export to CSV too).
Parsing the CSV is trivial, getting a logic level from it is also fairly easy. I realise that this is terribly quick & dirty but it worked 100% for what I needed. Here is the high level process

1. Ignore timings - SPI is clocked so actual timing is irrelevant for this analysis
2. Parse X and Y channels
3. Convert clock channel voltage into logic level 1 or 0
4. Discard all rows apart from rows where the clock goes high
5. Convert data channel to logic level
6. Group into bytes
7. Display hex value

As I said, very simple but it worked well and I was able to see exactly what was going on. Obviously this only works for synchronous (clocked) protocols like SPI/I2C but that is all I needed.

Here is the full F# script (also see the gist)