Skip to main content

S0 interface (pulse output)

The S0 interface is a standardized pulse output used by many energy and utility meters: electricity meters, gas meters, water meters and heat meters. Each pulse corresponds to a defined amount of consumed energy or medium, and STICKER Input counts these pulses, enabling remote consumption readout over the LoRaWAN network.

Wiring​

Connect the S0 output of the meter to input A or B as a dry contact: DIP switch S1 positions 2+4 for input A or 5+7 for input B (see STICKER Input Wiring).

Configuration​

Firmware v2.0.0 and later counts S0 pulses with the pulse input mode:

config cap-gpio-mode inputs
config cap-gpio-input-a pulse

Use cap-gpio-input-b pulse for input B.

How pulses are counted​

  • S0 pulses are at least 30 ms long, so a pulse input counts them in an interrupt instead of the regular 100 ms input poll.
  • Either polarity works: the level of the input at start-up is taken as the idle level, and every move away from it counts as one pulse, whether the meter pulls the line low or drives it high.
  • An edge counts only when the input was stable for 20 ms before it, so contact bounce counts once.
  • A pulse input always counts: the input-a-counter / input-b-counter setting is ignored.
  • A pulse input has no state: no state alarm is raised and input_a_is_active / input_b_is_active stays false.

The total arrives in telemetry as input_a_count / input_b_count. The counter channel (input-a-count / input-b-count) can also be recorded in the history and used in a RATE alarm rule, for example 100 pulses within 15 seconds (hi 100 dwell 15).

Known limitation

The pulse counter is not tested on hardware yet in firmware v2.0.0 (pulse timing and bounce in both polarities).