ALM-173-R1: 17 Inputs, 3 Relays, ESPHome/HA support

What Can It Do?

The ALM-173-R1 is a standalone, RP2350-based Modbus RTU I/O module designed for alarm logic, fault monitoring, access control, or any automation system that needs grouped inputs and relay outputs.

Key Specs:

• 17 opto-isolated digital inputs (for dry contacts like door/PIR/fault)
• 3 SPDT relays (siren, strobe, lock, etc.)
• 4 front buttons (acknowledge, override)
• 4 user LEDs (blinking or steady indicators)
• Group logic: momentary or latched (per group)
• RS-485 Modbus RTU interface
• WebConfig via USB‑C (Web Serial, no app)
• 24 VDC power, DIN-rail mountable

Real Use Cases

• The ALM-173-R1 works great as:
• Zone alarm panel (e.g. intrusion/fire)
• Access controller with door supervision
• Equipment room annunciator
• Smart Home I/O interface (via Home Assistant)

With built-in group logic, it can:

• Trigger relays when inputs go active
• Blink LEDs based on alarm states
• Acknowledge alarms via button or HA
• Mirror states over Modbus to PLC/HA

IN1 = door contact → Group 1 → Relay 1 = strobe → Ack by Button 1 or via HA

How to Configure It?

No software install required. Just connect USB-C and use your browser.

Quick Setup:

• Connect USB-C to your PC
• Open: WebConfig Tool
• Configure everything in-browser:

Modbus ID, baud rate:

Inputs → groups (with invert, debounce)

Alarm logic per group

Map relays, buttons, and LEDs:

• All from a clean Web Serial UI
• Live device status preview
• All settings stored in flash memory

How to Use It with Home Assistant(via ESPHome)?

The ALM-173-R1 integrates natively with ESPHome and Home Assistant.

Wiring:

• Connect ALM to MiniPLC/MicroPLC over RS-485 (A/B/COM)
• Set Modbus ID (e.g. 5) via WebConfig

ESPHome YAML Snippet:

uart:
  id: uart_modbus
  tx_pin: 17
  rx_pin: 16
  baud_rate: 19200
  parity: NONE
  stop_bits: 1

modbus:
  id: modbus_bus
  uart_id: uart_modbus

# ---------- Pull ALM Modbus entities from GitHub ----------
packages:

  alm1:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: ALM-173-R1/Firmware/default_alm_173_r1_plc/default_alm_173_r1_plc.yaml
        vars:
          alm_prefix: "ALM#1"
          alm_id: alm_1
          alm_address: 5
    refresh: 1d

Home Assistant sees:

• Inputs IN1–IN17 as binary sensors
• Alarm states: G1, G2, G3, and Any Alarm
• Switches for relays, acknowledge, and override
• Live mirror states: LEDs, buttons, relays

✅ No HA add-ons required

✅ ESPHome does all the work

✅ Scalable with multiple ALMs (just use unique addresses)

Custom Firmware & Updates

The ALM-173-R1 is built on the RP2350 dual-core MCU and is 100% developer-friendly.

Supports:

• Arduino IDE
• PlatformIO
• C/C++ SDK

Update via USB-C:

• Press Buttons 1 + 2 = Boot mode
• Press Buttons 3 + 4 = Hardware reset
• Flash via Arduino/PIO

This project is open hardware + open firmware:

Schematics: https://github.com/isystemsautomation/HOMEMASTER/tree/main/ALM-173-R1/Schematics/

Firmware: https://github.com/isystemsautomation/HOMEMASTER/tree/main/ALM-173-R1/Firmware/

Web Serial: https://github.com/isystemsautomation/HOMEMASTER/tree/main/ALM-173-R1/Firmware/ConfigToolPage.html

No cloud dependency — everything runs locally and transparently