Digital outputs

Four outputs sit on pins P0…P3 of the PCF8574 (o1 = P0 … o4 = P3), on the same I2C bus as the LCD and SHT41. Pins P4…P7 are used by the touch buttons; both live on one chip.

All outputs are off by default (oN_en = false): a slot that is not enabled is not shown, not reported, and the output command for that slot is rejected. Enable a slot through configuration, then switch it with the output command or rules. All keys take effect without a reboot.

Key	Default	Function
oN_en	false	slot enabled. false = pin forced OFF and commands rejected
oN_active	low	the pin level that means ON. low: ON = pin pulled low (suits LEDs or active-low relay modules, and keeps the output off at power-up). high: ON = pin high
oN_label	O1…O4	name for the LCD, max. 11 characters
oN_name	empty	metric name (e.g. siren); empty = slot ID. Unique across all slots and must not be a reserved name

Switching an output

Over the cmd topic:

{"action":"output","output":"o1","state":true,"seconds":30,"id":"req-7"}

Field	Required	Notes
output	yes	o1…o4, or the metric name of an enabled slot (oN_name)
state	yes	true = ON, false = OFF (boolean)
seconds	no	only with state: true: the output turns OFF by itself after 1…86400 seconds (relay pulse). Without seconds, the output stays on until switched off or reboot
id	no	returned in cmd/result

Result in cmd/result: {"ok":true,"msg":"siren HIDUP selama 30 s"}. Rejected (ok:false) if the slot is unknown or oN_en = false, state is not a boolean, seconds exceeds 86400, or the PCF8574 does not answer.

Alternatives: python3 Tools/celestianctl.py cmd <mac> output output=o1 state=true seconds=30, out o1 on 30 in USB serial, or the Control tab of the web interface.

Reporting

• Telemetry carries a boolean metric oN_name for each enabled slot (true = ON, independent of oN_active).
• Every change (from a command, the seconds timer, a rule, or slot disabling) is sent as an event. A slot disabled while ON automatically turns OFF, and an OFF event is sent once before its metric disappears.
• Telemetry carries expander_ok (boolean). false = the PCF8574 does not answer: buttons are dead, output state cannot be trusted, and the output command is rejected.
• The LCD has an OUTPUT page when any slot is enabled: HIDUP (ON) / MATI (OFF), or I/O ERR if the PCF8574 does not answer.

What to know about the PCF8574

Current limits and state on reset

• Pins only sink current well. One pin sinks ±25 mA, but sources only ±100 µA when high. A small LED (to 3V3 through a resistor, cathode to the pin) can be driven directly; other loads need a transistor, optocoupler, or relay module.
• Every boot, all outputs are OFF. State is not stored; the server or a rule switches them on again if needed.
• The PCF8574 has no reset pin. If only the ESP32 is reset while the 3.3 V supply stays up, the chip keeps the pin state until the firmware rewrites it at the start of boot (a few hundred milliseconds). For loads that must not turn on during that time, use a safe driver (e.g. an optocoupler that defaults to off), and do not rely on the pin alone.

The firmware rewrites the output state to the chip every second, so a chip that briefly loses supply returns to the correct state.

Outputs and rules

On-device rules can take control of outputs with the out action (true, false, or follow). Manual commands keep working and win until that output’s next rule transition. Only one follow rule may control an output.