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CoHost setup

Overview

The CoHost provides continuous health monitoring for your SenArch ARCH-1 Standard LoRaWAN Gateway through an independent LoRaWAN connection. It reports solar, battery, temperature, and humidity status continuously and runs on its own backup battery, which lasts at least one month of transmissions. The CoHost also accepts remote commands over LoRaWAN — for example, if the gateway loses its LTE connection, you can reboot it over LoRaWAN. It also includes tamper detection sensors that trigger immediate alerts when the gateway enclosure is opened (PIR sensor) or falls (accelerometer).

Prerequisites

Get the CoHost LoRaWAN keys

The CoHost keys are shown in the Gateway UI.

  1. In the Gateway UI, open Dashboard → CoHost Info & Controller.

  2. Press Refresh CoHost Info. The gateway reads the keys from the CoHost and displays them (this can take up to 30 seconds):

    • DevEUI — device identifier
    • JoinEUI — application identifier (also called the AppEUI)
    • AppKey — security key

Each value has a copy button. The section also shows the CoHost serial number (chXXXX), software version, and transmission interval.

Register the CoHost in your network server

  1. Access your LoRaWAN network server.
  2. Create a new device registration.
  3. Name the device using the CoHost serial number (chXXXX). Include the gateway serial number (archXXXX) as well — for example archXXXX-chXXXX — so you can tell at a glance which gateway the CoHost belongs to.
  4. Enter the DevEUI, JoinEUI (AppEUI), and AppKey from the Gateway UI.
  5. Set the device profile to LoRaWAN 1.0.4.
  6. Set the device region frequency.

The CoHost operates as a standard LoRaWAN Class A device.

Data monitoring

The CoHost transmits health data in structured LoRaWAN payloads containing solar panel voltage and current, battery charge level, internal temperature and humidity, gateway operational status, and tamper detection alerts. When tamper sensors activate, the CoHost wakes outside of its scheduled transmission cycle to send an immediate alert.

SenArch dashboard: contact SenArch for a pre-configured application server with a real-time monitoring dashboard.

Custom integration: use the payload specification below to implement monitoring in your own system.

Payload specification

The CoHost transmits a 48-byte binary payload with little-endian byte order:

Field Name Offset (bits) Size Type Units
Solar Bus Voltage 0-31 4 bytes float LE V
Solar Current 32-63 4 bytes float LE mA
Solar Load Voltage 64-95 4 bytes float LE V
Battery Bus Voltage 96-127 4 bytes float LE V
Battery Current 128-159 4 bytes float LE mA
Battery Load Voltage 160-191 4 bytes float LE V
System Bus Voltage 192-223 4 bytes float LE V
System Current 224-255 4 bytes float LE mA
System Load Voltage 256-287 4 bytes float LE V
Temperature 288-319 4 bytes float LE °C
Humidity 320-351 4 bytes float LE %RH
PIR Event Detected 352-359 1 byte uint8 boolean
Fall Event Detected 360-367 1 byte uint8 boolean
CoHost Battery Charge 368-375 1 byte uint8 %

Health uplinks are sent on FPort 10. For The Things Network, download this example payload formatter and paste it into your application as the uplink decoder:

Download the TTN decoder example

Downlink commands are processed only after an uplink (Class A behavior). The firmware reads only the first byte of the downlink payload as the command value; any additional bytes are ignored. Unknown commands are ignored.

FPort Command (hex) Payload Action Persists
13 0x50 (80) 1 byte Restart the Main-Host. No
20 0x01–0xFF 1 byte Set the transmission interval, in minutes (1–255). Yes

CoHost controls (Gateway UI)

Dashboard → CoHost Info & Controller also has buttons to manage the CoHost:

The CoHost controls in the Gateway UI

  • Clear Session and Nonces — clear the LoRaWAN session state and the nonces, so the CoHost rejoins the network from scratch. Requires your admin password.
  • Clear Nonces — clear the CoHost's stored LoRaWAN nonces (used for replay protection during OTAA joins). Try this if the CoHost cannot rejoin the network. Requires your admin password.
  • Set Transmission Interval — change how often the CoHost wakes and transmits (3–255 minutes). A shorter interval sends updates more often but uses more power; a longer interval is quieter but reports less frequently. The value is stored on the CoHost.
  • Reset CoHost — wake and restart the CoHost, even if it is asleep. LoRaWAN session data and nonces are kept; traffic pauses briefly while it restarts.
You may also need to reset the device on your LNS

After Clear Nonces or Clear Session and Nonces, if your network server (or Join Server) still holds the old nonce or session state, joins can be rejected until you reset the device on the LNS side as well.

Next steps