2018-02-15, 07:44 PM
(This post was last modified: 2018-02-15, 07:50 PM by seandepagnier.)
Using ratiometric cable and voltage signal.. if the cable is bad the wind speed will be 0, and the direction random. It is usually obvious there is a problem if the wind direction never changes.
It is nice to detect a problem in the cable. It is annoying to read 40mA though. Unless you have an amplifier and low ohm resistor, you need at least 30 ohms. This wastes quite a bit of power, up to 100mW, not to mention losses in the cable.
It might make more sense to put the uC in the sensors and send digital data down the cable.
For wireless... I don't really like it, because you already need a cable to supply power. Maybe 2 wires instead of 4, but wireless links also may have lag which can be bad and may be difficult to diagnose problems.
For signalk vs nmea0183... You probably are going to want both anyway for the foreseeable future. kplex converts nmea0183 to signalk. So for this reason, unless you have more interesting data than only speed and direction, what do you gain by using signalk here?
For wasting a usb port. It's possible to use any pin on the raspberry gpio header as a virtual serial port. It consumes a few % cpu, but it isn't really an issue with low data rates especially with 4 cores
pypilot can get the wind data from different sources, It can receive from opencpn, or kplex for example, but this adds lag. lag is bad in the autopilot control loop, so for this openplotter defaults to setting kplex to read the wind data from pypilot which reads the data directly from the sensor on a serial port. So the autopilot has it first. If you don't use the autopilot, then it's not important, and can be configured differently.
It is nice to detect a problem in the cable. It is annoying to read 40mA though. Unless you have an amplifier and low ohm resistor, you need at least 30 ohms. This wastes quite a bit of power, up to 100mW, not to mention losses in the cable.
It might make more sense to put the uC in the sensors and send digital data down the cable.
For wireless... I don't really like it, because you already need a cable to supply power. Maybe 2 wires instead of 4, but wireless links also may have lag which can be bad and may be difficult to diagnose problems.
For signalk vs nmea0183... You probably are going to want both anyway for the foreseeable future. kplex converts nmea0183 to signalk. So for this reason, unless you have more interesting data than only speed and direction, what do you gain by using signalk here?
For wasting a usb port. It's possible to use any pin on the raspberry gpio header as a virtual serial port. It consumes a few % cpu, but it isn't really an issue with low data rates especially with 4 cores
pypilot can get the wind data from different sources, It can receive from opencpn, or kplex for example, but this adds lag. lag is bad in the autopilot control loop, so for this openplotter defaults to setting kplex to read the wind data from pypilot which reads the data directly from the sensor on a serial port. So the autopilot has it first. If you don't use the autopilot, then it's not important, and can be configured differently.