LED control lines

Driving LEDs

The outputs are 3.3 V TTL level with a maximum source/sink current of 4 mA. An external series resistor must be used to limit the current. The value of the series resistor in Ohms is determined by:

(3.3-Vf)/(If) > Rs > (3.3 V - Vf)/(.004)

Rs = Series resistor

If = LED forward current, max typical If of the LED should be less than 3 mA

Vf = LED forward voltage, max typical Vf of the LED should be less than 2.7 V

Most LEDs can be driven directly as shown in the circuit below:

LEDs that do not meet If and Vf specification must be driven with a buffer to ensure proper voltage level and source/sink current.

Power LED

This active-high line indicates that the unit is powered on.

Satellite LED

This active-high line indicates that the unit has acquired satellites.

A rapid flash indicates that the unit has less than five satellites acquired, while a slow flash indicates greater than five satellites acquired. This line will stay on if the unit is in monitor mode.

RTK Correction

A slow flash indicates that the unit is receiving corrections. This will also flash when the unit is in monitor mode.