16 SAIL Instrument 1

Hardware

Our first target will be to match and extend the capabilities of the popular Velocitek ProStart instrument for sportboats and skiffs.

Outside Case of Sail 1 instrument
This prototype is housed in the original case from a Velocitek SC-1, the predecessor of the ProStart.

It’s only fitting to protect it from the elements in an old case from an earlier commercial instrument.

Inside the SAIL 1 Instrument
With the case open, there’s access to the power switch, USB, and a much clearer view of the components that make up the Instrument. The display provides diagnostics while the WiFi can provide data to display units located on the boat, or to a nearby coach boat in real time.

The first prototype was assembled on a solderless breadboard as a proof of concept, however the connections were unreliable in a marine environment, especially if the system was exposed to spray. This version includes a feather processor module on the left and an instrumentation module on the right, along with a battery. Separating the instrument system from the processor provides the option of exploring performance capabilities of different processors. The initial combination includes:

Note that the trace for the wake pin on the M0 WiFi was cut on the underlying prototyping wing to allow the cable harness connection to include a ground pin.

Timing Considerations

There are multiple sources for time of day. The WiFi can provide NTP time if there’s a connection. The GPS provides time of day, but may be a little off due to the latency of the serial communication, and some jitter has been seen at the fractions of a second level. The RTC needs an initialization source from somewhere to re-sync. The millis() clock gives a long time base that increases monotonically and has very little latency.

We don’t want the time base to shift in the middle of a measurement.

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