Alarm Engine & Rules (alarm)
The STICKER Alarm Engine continuously evaluates sensor measurements and system states against active rules. When a rule condition is met or cleared, an immediate uplink payload is generated and sent on fPort 3.
Rules are managed over the developer console using the alarm command (see Firmware Setup) or configured remotely via NFC and LoRaWAN downlinks (set_param on fPort 85).
The Alarm Engine described on this page is a core capability introduced in STICKER firmware v1.4.0. It supports dynamic multi-slot threshold rules, state transitions, pulse rate limits, system health monitoring (low-battery, watchdog), and immediate event uplink reporting on fPort 3.
Global Rate Limiting & System Alarms
Global alarm rate limiting is controlled via the config alarm-limit parameter:
| Command | Argument | Description |
|---|---|---|
config alarm-limit | 0-3600 (seconds) | Minimum interval between consecutive alarm uplinks. The first event triggers an immediate uplink; subsequent alarms within this window are queued or suppressed. 0 = rate limiting disabled. Default 0. |
Built-in System Alarms
In addition to user-configured dynamic rules, firmware v1.4.0 automatically manages two system-level health conditions:
- Low-Battery Alarm: Triggered when battery voltage drops under load below critical operational thresholds. Reported via fPort 3.
- No-Data Watchdog Alarm: Monitors internal sensor sampling. If a physical sensor fails to respond or misses successive sampling windows, a watchdog alarm is raised on fPort 3.
Dynamic Alarm Rules
Per-sensor thresholds are held in 16 fixed slots (0-15). The slot index serves as the rule's stable identifier, allowing multiple rules (e.g., warning vs. critical levels) to monitor the same sensor slot simultaneously.
| Command | Description |
|---|---|
alarm list [<index>] | List all active alarm rules or inspect a specific slot. |
alarm set <index> <source> <quantity> <args> | Write a rule into a designated slot (0-15). |
alarm new <source> <quantity> <args> | Assign a rule to the first available free slot. |
alarm clear <index> / alarm clear all | Delete a single rule slot or purge all active rules. |
alarm poll | Force an immediate sample and evaluation of all active rules (useful for bench testing). |
Rule Sources
| Source | Sensor Target |
|---|---|
onboard | On-board sensors (temperature, humidity, atmospheric pressure) |
s1 - s4 | 1-Wire sensor channels 1 to 4 |
hall-left, hall-right | Integrated magnetic door switches |
input-a, input-b | External industrial inputs |
pir | PIR motion detector |
accel | 3-axis accelerometer |
Quantities & Rule Types
| Quantity | Kind | Arguments | Supported Sources |
|---|---|---|---|
temperature, humidity, pressure | threshold | <lo> <hi> [dwell] | onboard; temperature/humidity also on s1-s4 |
illuminance, magnetic-field | threshold | <lo> <hi> [dwell] | s1-s4 |
tilt | state | <from> <to> [dwell] | s1-s4 |
state | state | <from> <to> [dwell] | hall-*, input-*, pir, accel |
count | rate | <N> [dwell] | hall-*, input-*, pir, accel |
- Threshold Rules: The alarm triggers when a measured value crosses outside the
[lo, hi]window. - State Rules: Evaluates
<from> <to>digital levels (0/1).from != torepresents an edge (triggers once upon transition);from == torepresents a level (active while line equalsto). Momentary sources (pir,accel) only accept edge rules. - Rate Rules: Fires if counter accumulation exceeds
<N>events within a single report interval.
The dwell Parameter
The optional dwell duration (in seconds, default 0) provides integrated noise filtering and hysteresis. It prevents false triggers from minor signal spikes or rapid input chatter.
| Rule Kind | dwell Behavior |
|---|---|
| Threshold | Value must continuously stay outside [lo, hi] for dwell seconds before activating. Returning inside the band deactivates the alarm immediately. |
| State (Edge) | The line transition must hold steady for dwell seconds before triggering. Once triggered, the rule enforces a cool-down window of dwell seconds before it can re-fire. |
| State (Level) | Line must remain in state to for dwell seconds continuously before triggering. |
Momentary (pir, accel) | Enforces a cool-down window of dwell seconds before a new motion event can trigger an alarm. |
| Rate | Hold-off time enforcing minimum spacing between successive rate limit alerts. |
Command Examples
alarm set 0 onboard temperature 5 30 # Alarm below 5 °C or above 30 °C (immediate)
alarm set 1 onboard temperature 5 30 60 # Alarm below 5 °C or above 30 °C (must hold for 60 seconds)
alarm set 2 input-a state 0 1 # Fire on rising edge (0 to 1) on External Input A
alarm set 3 input-a state 0 1 5 # Rising edge on Input A must hold for 5 seconds
alarm new hall-left count 10 # Alarm when left hall sensor exceeds 10 counts per interval
alarm list # Review all programmed alarm rules
alarm clear 1 # Erase rule in slot 1
Alarm rules can also be generated and updated over LoRaWAN or NFC using binary downlink payloads on fPort 85. Use the Downlink Commands Generator to build binary downlink strings for your network server.