Home Assistant

Booking calendars, occupancy sensors, locks in both directions, access events, meter readings and room displays with the Home Assistant integration.

With the inwendo ERP integration for Home Assistant, you control your building according to your bookings in vynst (inwendo ERP): heating on before training, lights off after it ends, door open for the booked group. The integration is open source: github.com/inwendo/iw_erp_homeassistant.

What you get

Feature	Default	Switch in vynst
Calendar per room or object, updated instantly via webhook, otherwise every 15 minutes	on	none
Locks from vynst as Home Assistant locks	off	none
Open locks from Home Assistant in vynst, with vynst’s access rules	off	none
Occupancy sensors: occupied, lead time, open, next booking, participants	off	`integration_occupancy_api_enabled`
Events `iw_erp_access` and `iw_erp_check_in`, sensor “Last access”	off	`integration_ha_access_events_enabled`
Service `check_access` for card, QR and keypad readers	none	`integration_ha_access_check_enabled`
Service `create_ticket`, for example for a water alarm	none	`integration_ha_ticket_enabled`
Meter readings from vynst as sensors, Home Assistant counters reported to vynst	off	`integration_usage_counter_api_enabled`
Room displays on OpenDisplay e-paper signs	off	none

The switches in vynst are under Settings → Smart home & automation (Einstellungen → Smart Home & Automationen) and are off by default. If a feature is off in vynst, the integration skips it and writes an info line to the log.

Installation

In Home Assistant, open HACS → Integrations → ⋮ → Custom repositories (HACS → Integrationen → ⋮ → Benutzerdefinierte Repositories).
Add https://github.com/inwendo/iw_erp_homeassistant as an Integration, install “inwendo ERP” and restart Home Assistant.
Go to Settings → Devices & services → Add integration → inwendo ERP (Einstellungen → Geräte & Dienste → Integration hinzufügen → inwendo ERP).
Enter the address of your instance (https://your-instance.iw-erp.de) and an API token.

Home Assistant 2025.1 or later is required.

API token

Create the token in vynst, in your user settings under API access. It needs these rights:

Right	Purpose
Read locations (`location`)	read rooms and objects, occupancy, room displays and meters
Write locations (`location`)	report meter readings
Read and write bookings (`event_booking`)	calendar and webhook sign-up
Write events (`event`)	offer locks to vynst, `check_access`
Write tickets	`create_ticket`

Also restrict the token to the path /api/homeassistant/.*. The .* at the end is required so that the pattern works as a prefix.

Webhook

During setup, the integration registers a webhook with vynst itself (POST /api/homeassistant/webhook). When a booking changes, vynst sends an update immediately.

vynst only accepts https:// addresses with a public hostname. Home Assistant therefore needs an external URL (Settings → System → Network, or Home Assistant Cloud). Without one, the integration polls regularly and reports this under Repairs.
vynst sends the token that was passed during registration back as X-IW-Webhook-Token. Only then do events arrive with verified: true. Check verified before an automation does anything security-relevant.

Locks in both directions

Importing locks from vynst: For every lock that the token’s user may open, a lock is created in Home Assistant. Opening goes through vynst, which checks the rights and writes to the lock log.

Offering Home Assistant locks to vynst: You select locks. The integration reports them, and every state change, to vynst. There they appear as a smart lock connection with the name of your Home Assistant. Only after an administrator syncs the devices in vynst and grants rights can anyone open them. Commands from vynst are signed:

Header X-IW-Signature: HMAC-SHA256 over the content, with a key that only this installation and vynst know
Commands older than two minutes, or sent twice, are rejected
Only selected locks are accepted. Locks imported from vynst cannot be offered back.

Examples

Light on with the first check-in in the studio:

triggers:
  - trigger: event
    event_type: iw_erp_check_in
    event_data:
      attendance_list_name: Fitnessstudio
      checked_in: true
actions:
  - action: light.turn_on
    target:
      entity_id: light.studio

RFID reader checks with vynst and opens the door:

triggers:
  - trigger: event
    event_type: esphome.rfid_scanned
actions:
  - action: iw_erp_homeassistant.check_access
    data:
      credential: "{{ trigger.event.data.uid }}"
      credential_type: card
      lock: lock.haupteingang
    response_variable: access
  - if: "{{ access.granted }}"
    then:
      - action: lock.open
        target:
          entity_id: lock.haupteingang

The response contains granted, reason (granted, unknown_credential, no_access, invalid_code, code_expired), person and opened.

Ticket for a water alarm, without duplicates:

actions:
  - action: iw_erp_homeassistant.create_ticket
    data:
      title: Water alarm hall 1
      bookable_id: 7
      priority: urgent
      dedupe_key: water_leak_hall_1

Blueprints

Three ready-made automations work with the calendars only: Preheat room before each booking, Light for booking and Frost protection outside bookings and opening hours. Import them via the link in the README. A room’s lead time comes from its field automation_pre_start_minutes in vynst, otherwise it is 30 minutes.

Room displays

In vynst, under Rooms & resources → Room displays (Räume & Ressourcen → Raum-Displays), create a display of type OpenDisplay. In Home Assistant, you assign an e-paper sign to it. Home Assistant fetches the image from vynst (/api/homeassistant/displays/{id}/frame.png, with ETag), transfers it via Bluetooth and reports the battery level and the last contact back. If the battery is low or the display fails, vynst sends an email to room management.

API

The endpoints under /api/homeassistant/ are listed under Smart home and automation. vynst runs its own contract tests against them so that the integration does not break on updates.