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@ -42,6 +42,12 @@ The transmitter output is 2 Watts (+33dBm) and it has a verified range of over 1
The unit runs on 12V and exposes a 3.3V UART for connecting to the rest of the boat's system. The UART continuously sends GPS and AIS data in NMEA0183 format at 38.4Kbps. The breakout boxes pictured above deliver this stream via USB, NME0183 (RS422) or NMEA 2000 (CAN). All 3 breakouts feature **galvanic isolation** of their USB connection to avoid causing unintended problems with laptops and other devices whose power supplies are meant to "float".
In addition, there is now a "bare bones" UART breakout:
<img src="images/uart_breakout.jpg" height="420"/>
This provides the simplest, lowest cost interface to a Raspberry Pi (assuming the UART is available).
For the circuit to transmit, it must be configured with persistent station data (MMSI, call sign, name, dimensions, etc). This is stored in MCU flash and is provisioned over a USB/serial connection via a command line interface. If station data is not provisioned, the device will simply run as a 2 channel receiver.
The unit implements SOTDMA synchronization based on the very acurate 1 PPS signal from the GNSS and the UTC clock, but being a class B, it will not attempt to reserve time slots. It will just transmit autonomously and independently, based on Clear Channel Assessment, at the schedule permitted for class B devices.