lifting keel sensor, how to integrate ?

[PaddyB]

Hi,

I have a boat with a lifting keel. I know it is not that common. But i would like to make a sensor which tells me the position of the lifting keel.

So I've found a sensor which measures distance. This sensor has an I2C interface. And there is an C arduino library available, which arrange calibration, measuring etc.

On the end I would like to have a signal K format signal, which can be displayed.

Code:

/vessels/<RegExp>/design/keel/lift

Units: ratio (Ratio)

Description: In the case of a lifting keel, centreboard or daggerboard, the part of the keel which is extended. 0 is 'all the way up' and 1 is 'all the way down'. 0.8 would be 80% down.

related to this is of course 

Code:

Description: Depth related data

/vessels/<RegExp>/environment/depth/belowKeel

Units: m (Meter)

I now come to the implementation part and have several possibilities;

1. directly connect sensor to I2C bus of PI. I don't have a library, i think I have to program something in phyton ?
   
2. connect sensor to a small arduino board and use USB/serial interface to communicate between (sensor/arduino) and openplotter 
   a. native like described in: part2  and part 3
   

          b. via MQTT between (sensor/arduino) and OP/PI sending native or JSON messages
          c. via NMEA 0183 (Private) messages between (sensor/arduino) and OP/PI
      3. ??

I'm sailor and not an experienced programmer ..
Any suggestions are welcome

G.

I might  be worth looking at node red,  already installed in raspian,  just type "node-red"  in a terminal to check it out, very powerful. It has an i2c input so it may be a way to get the data and format a signalk message then send it out to openplotter. 
https://www.npmjs.com/package/node-red-contrib-i2c