Code to turn PyBoard with accelerometer into tilt current meter.

Assembly instructions and DIY project page:

https://hackaday.io/project/158083-cheap-underwater-tilt-current-sensor

This guide assumes that

• You are running Linux with Python 3 installed
• When connected PyBoard is available as /dev/ttyACM0

1. Connect battery
2. Right after PyBoard launch sequence press and hold USR button until green led blinks - that means board switched into Storage/Serial device mode. If you missed and orange LED started blinking (meaning that PyBoard started logging) press RST followed by holding USR button until green LED blinks a few times
3. Connect PyBoard to computer
4. Execute ./setrtc.py - this will set UTC time on the board based on computer time
5. Push RST button to recycle PyBoard. Press nothing else. If orange LED starts blinking that means PyBoard entered logging mode
6. Assemble the meter
7. Calibrate still vertical position by attaching meter tether to a bottom of a bucket/pool/container filled with water. Leave it like this to 10-20 logging cycles
8. Deploy the meter underwater
9. After desired period of time has been logged, unmount the meter and bring back to the surface
10. Dry it out and open the housing
11. Push RST button followed by pushing USR button to switch the board into Storage/Serial device mode
12. Execute ./checkpointrtc.py - this will measure and record difference between your computer clock and PyBoard clock. (PyBoard Lite has cheap oscillator as real-time clock and it is not precise. setrtc.py and checkpoint.py together establish cumulative error. That information will be used to calculate correction of record timestamps during log processing)
13. Download log *.csv files into some folder
14. Proposed scripts to use for log processing
    • average-sample-series.py - take all records within logging frame and average them to one record
    • axes_to_angle.py - convert axes values to angle between accelerometer (x,y,z) vector and vertical direction
    • pyboard-to-posix-timestampe.py - convert PyBoard timestamps to POSIX timestamps.