Digital inputs are available on the SensorData and SensorNode. These can be used to monitor the state of external devices or switches, or to count pulses - from a rain gauge, for example. The inputs have a maximum input of 48V, and anything about 2.5V or above is considered 'on'. 


Hardware Capabilities

SensorData LoRaWAN: 2 x DI on new stock. Only 1 for device serials lower than 70B3D5705000197D.

SensorData Sigfox: 3 x DI.

SensorNode LoRaWAN:  2 x DI.


Input Count

Input changes are always being counted on the inputs, and the count can be added to a schedule to be transmitted. Care must be taken when using the count values, as they are transmitted as 16 bit integers, and will overflow periodically. Readings should be compared to their last reported value, and the difference (modulo 65536) used to increment a larger counter on your backend. Additionally:

  • On the SensorData LoRaWAN, before firmware v2.2, and the SensorNode LoRaWAN before v2.4, the input counts would reset to zero when power was removed. There was no reliable way to detect this, as the reset message is sent for all resets, not just resets due to power removal.
  • In the latest firmware versions, the input counts are monotonic and non-volatile, so you don't have to handle resets to zero.


Alarms

An alarm message can be sent, if set up, when an input changes to a certain value. Care must be taken with the parameters to ensure that alarms can't be generated too frequently for the LoRaWAN network in use. 


Global Parameters

Alarm Rate Limit (s)

The minimum time between alarm transmissions. If an alarm occurs before this time has passed (from a previous alarm), it will be ignored. Default is 600s (10 minutes).


Per Input Parameters

Pull direction:

See explanation here. By default this is set to pull down. Note: Using a pull up on inputs slightly increases the sleep current of the device, which will affect the battery life.


Alarm On High/Low:

Enabling either of these will send an alarm message when the condition is met, ie, Alarm on high enabled = sending message when the input turns on. Default is disabled for both.


Count Edge:

Sets if the input count is incremented when the input turns on, or off. Default is high (count when input turns on).


Debounce Period (ms):

The input has to change for this amount of time for the change to be detected. Default value is 1000 ms (1 second).

The debounce period determines the rate at which the pulse changes are recognized. The minimum practical debounce period is about 50ms.