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Peripherals and services

Board peripherals and system services

How the panel works with the ADS1115 analog-to-digital converter, with fitted retentive memory (FRAM/EEPROM) and with a real-time clock (RTC). Technical background: specs/007-peripherals-services/.

ADS1115 — analog inputs (project peripheral)

You connect the converter to the I2C header of the board and add it in the editor as a peripheral (exactly like the TCA9555 expander) — the procedure is shown in the clip Adding peripherals to a board:

peripherals:
  - { type: ADS1115, name: adc1, bus: i2c, addr: 0x48, range: 4.096 }
tags:
  - name: temperature
    datatype: f32
    source: { periph: { chip: adc1, pin: 0 } }   # pin = channel AIN0..3
    gain: 0.0125      # raw value -> physical units
    offset: -40.0
    deadband: 0.5     # mandatory on analog tags — filters noise
    unit: "°C"
  • The address is 0x48–0x4B depending on the chip's ADDR pin; range is the full-scale range in volts (6.144 / 4.096 / 2.048 / 1.024 / 0.512 / 0.256, 4.096 without the key). The raw value is 16-bit signed; with single-ended wiring 0..32767.
  • The channels are measured in turn, each one is refreshed within 4 PLC cycles at the latest (40 ms with a 10 ms cycle).
  • A disconnected or unfitted chip: one event in the diagnostics, the tags hold their last value, the panel keeps running; once it is connected the chip comes back to life on its own.

Retention — values that survive a power-down

Tags in the RVAR (retain) list are stored automatically according to what the board has fitted — nothing is configured:

The board has Behaviour
FRAM changes are stored within 1 s; no write-count limit
EEPROM changes are stored within 5 minutes at the latest (to preserve chip life — even with a permanently changing value it lasts > 9 years)
nothing internal flash (NVS), stored within 10 s — the original behaviour
  • The image in memory is protected by a checksum in two alternating copies — a power failure in the middle of a write can never corrupt both; after startup the last complete state applies.
  • Changing the list of retain variables (a different project/version) means the variables start from their initial values plus an entry in the diagnostics. Values are never mixed up between variables.
  • If the board catalog declares memory but the chip does not answer, the panel reports it and falls back to NVS — retention never stops working.
  • Capacity: 64 retain variables (NVS: 16).

For frequently changing values (piece counters updated every cycle) FRAM is the right choice — EEPROM only stores them once every 5 minutes.

Real time (RTC)

A board with a PCF8563 fitted (battery-backed) knows the date and time even after a power-down. Alarms and diagnostics then carry the real time.

Setting the time:

  • Service cable: python tools/settime.py COM5 --apply (sets it from the PC; without --apply it only prints the time), or the serial command VUT!2026-08-09 14:32:05 directly.
  • WEBview: the "Set panel time" button in the status bar — it takes the time from the phone/PC. The button only appears on panels that support setting the time.

States (VUT! prints source= and state=):

  • rtc / ok — the time runs from the RTC chip and survives a power-down
  • sys / none|invalid — there is no RTC (or its battery is flat): the time is valid until power-down, after a restart it begins at 2000-01-01; a flat battery is reported by the diagnostics

The time is local — the panel does not deal with time zones or daylight saving; at the changeover set the time the same way you would on a machine with a Simatic.

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