# GNSS Compass Main (4-pin) RS-232 Connection

The GNSS Compass modules drive longer cable lengths than can be done reliably with TTL-level serial signals. The ROVL-ethernet PC board is set up to accommodate this.

  The GNSS Compass modules expect DC power (Vin) of 4.1V to 5V.

{% hint style="info" %}
The GNSS Compass main connection is RS-232. Many modern serial ports call themselves "RS-232" but are actually TTL or CMOS level signals of 0V to 3.3V or 0V to 5V. The GNSS Compass modules use actual RS-232 signaling of -12V to +12V with the signal sense inverted from the TTL signals. Connecting a GNSS Compass Module to a TTL serial port will likely damage the TTL port.
{% endhint %}

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