The G120 has 2 switched ground digital outputs and 1 switch power output.
- Switched Ground Digital Outputs
- Digital Output 1 - Pin 11 - Yellow
- Digital Output 2 - Pin 10 - Green
- Switched Power Output
- Pin 9 - Orange
Switched Ground Outputs
Switched ground outputs provide a path to ground when 'on' (i.e. allow a path for current, closing the circuit) and are high impedance when off (breaking the circuit). This is an example of a low side switch.
The function of the digital output can be set in system parameters. Functions include:
Setting the function dictates what 'controls' the output. i.e.
- if we set the output up with the function as Immobiliser - when the immobiliser should be on according to the device, the output is on.
- If we set it up as a Buzzer - this output will pulse on/off when buzzing should happen (i.e. if no driver ID is scanned) -so that if it is connected to a buzzer we will hear the buzz.
The active level setting depends on what we are using the device for and how is wired. The active level can be used to invert the output.
LED's and Buzzers should generally be Active High and Immobilisers Active Low.
Switched Power Output
Instead of providing a ground when on, and disconnected when off - these outputs provide a voltage source when on. The G120 will provide 5V at the pin when on. In this case, we wire the negative terminal of the buzzer to ground, and the positive side to the Switched Output wire.
Parameters are the same as for Switched Ground Outputs. You can set the function to determine what causes the output to turn on or off.
Remote Switching via the Server
Digital Outputs can be used for remote switching. i.e. to turn a pump or lighting tower off or on.
One example is how a vehicle can be immobilised by sending a command from the server - which is covered here Immobilisation Install - Asset can be immobilised from server [G120]. Telematics Guru has an 'immobilise' button, which causes a message to be sent down to the device to turn any outputs set up with function "Immobiliser" on or off. This same message can be sent from a 3rd party server using the OEM WebAPI - contact DM support for documentation.
Any outputs set up with function "Digital Output" can similarly be controlled by sending a different message to control outputs.
Remote Switching Latency
It is important to note that all of our devices (even hard-wired vehicle trackers) will sleep during periods of inactivity. For example, the G120 default tracking parameters are for the device to heartbeat hourly when the ignition is off and the asset is stationary. Between heartbeats, the device will sleep and the cellular modem will be off.
This means that a command sent down to the device will not be received until the next heartbeat, when the device next connects.
If we require low latency output switching, to improve upon this, we can set this parameter under the upload settings, available on hard-wired devices.
This will cause the device to attempt to remain connected to the network all the time. In practice, generally the network will kill the connection after 5-10 minutes. So the device additionally needs to be set to upload often enough to keep the connection alive. This can be done by setting the heartbeat interval to a sufficiently short window (may require some experimenting)
This will allow commands to toggle outputs to be received by the device within 60 seconds in most cases. It should be noted that this functionality was not designed with live control applications in mind.