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Digital Inputs Introduction - Dart3

The Dart3 has 1 x Ignition Digital Input and 3 x Digital Inputs with configurable pull up/pull down parameters. 

These inputs detect the voltage at the input, check it against the thresholds, and then record the digital input as on "1" or off "0". This can be used to determine the state of an asset, for example:

  • Door open/close
  • Ignition on/off
  • Pump on/off
  • Button presses
  • Pulse counting

This article provides general information about Digital Inputs on the Dart3. Specific set up examples/wiring guides can be found in subsequent articles.

Digital Input Specs

  • Input voltage range = 0-48V. This can technically be exceeded without damaging the device, but the input will not work properly outside of this range. 
  • On/Off Thresholds
    • Pull Up Enabled
      • Input registers low/off below 0.4V
      • High/On above 1.9V
    • Pull down enabled
      • Registers low/off below 0.8V
      • High/On above 2.2V

Bias Resistors

The Dart3 has a configurable 'Active Level' and Bias Resistor. 

  • The Active Level determines the physical line level (high or low) at which the input is considered on. 
  • The Bias Resistor essentially determines the state of the input when nothing is connected to the input. Since often we would leave them disconnected, or 'open circuit' meaning the state isn't well defined. The bias resistor handles this.

There are 3 options:

  • Pull up: pull the input high
  • Pull down: pull the input low
  • Disable: do not bias the input

These options are useful when one of the states being read is open-circuit (disconnected/high impedance). In this case, enable the bias resistor setting in the opposite state to the level being switched to.  This is commonly used when working with an "open collector" output. The pull up/down is a "weak" pull up/down.

Results of different configurations.

Bias ResistorActive LevelInputResult
 Pull DownHigh

Pull DownLow

Pull UpHigh

Pull UpLow


Setting Up a Digital Input

To set up either Digital Input 1, 2 or 3, you will need to use the corresponding wires. (See DART3 12-wire Harness Definition)

  • Digital Input 1 = PINK
  • Digital Input 2 = BLUE
  • Digital Input 3* = GREEN

*Digital Input 3 is shared with one of the Driver ID lines, so DI3 cannot be used at the same time as a DM RFID reader, or Wiegand Reader.

Then we can add the corresponding parameter tab to apply the right settings.

Function - Either Digital Input or Pulse Counting.

Digital Input - The virtual input number that you want it mapped to.

Bias Resistor and Active Level - See table above.

Log/Upload on Active - By default, the device will only log a record when the input changes. It is not immediately uploaded. In most cases we want to turn this on. So set Upload on Active/Inactive to Yes

Buzzing Parameters - We can optionally have any buzzers connected to notify us that the input is on/off.

Emergency Uploads - A device can be set to not upload in certain areas. This can be set up as part of Geofence Downloads to Device. If the Emergency Uploads is set to Yes, then the device will upload even in a no comms zone.

Config 1 - Debounce Time. By default, the input must stay on continuously for 1000ms = 1sec for the device to register it as on and send an update to the server.

Digital Input 3

To use Digital Input 3, set the 4 Wire Plug Function to iButton/Digital Input 3

Buzz on Active/Inactive

We can configure the Dart3 to sound any connected buzzers, or flash an LED, when an input is active/on or inactive/off. 

This can be very useful for providing feedback to drivers/operators, for example:

  • Sounding a buzzer when a seatbelt is undone or a tailgate is open.
  • Sounding a buzzer when a duress button has been pressed, to provide feedback that it was registered (note, this doesn't confirm that it has been received by the server). This can also help prevent false alerts as drivers are notified of accidental presses and can contact response teams. 

We can configure buzzing with these parameters. Setting the count to 255 enables continuous buzzing, for the entire time an input is on/off.

Example - 3 beeps when an input goes active.

This would result in the below when the input goes active:

Buzzer on 20ms -> off 20ms -> on 20ms -> off 20ms -> on 20ms -> off 20ms

Example - Continuous buzzing when an input is on, long buzzes (500ms on/off)

Buzz only when the ignition is on

We may want to set up the Dart3 to buzz when an input is active, and the ignition is on. i.e. we want to buzz if the tailgate is left open and the engine is running. We can solve this using the Input Monitor

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