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Forest Rock SMS Driver - Teltonika Firmware Issue Explained

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Training Guide: Downgrading Teltonika Firmware for Forest Rock SMS Driver (Niagara)

Last Updated: January 30th 2026
Applies To:Teltonika RUT241 / RUT9xx / TRB500 (Firmware 7.14 Works with our SMS Driver)
Audience:Field Engineers, Support Technicians
Purpose:Ensure Teltonika modems run a firmware version compatible with the Forest Rock SMS Driver used by Niagara Supervisors and JACEs.
SMS Driver Installation Guide:Forest Rock Downloads Site

Overview

We’ve found that the Forest Rock SMS Driver depends on a very specific, older set of AT‑command behaviours inside Teltonika modems. Over the last few firmware releases, Teltonika have changed how those SMS commands work, and that’s what leads to the odd issues we’re seeing, things like HTTP 422 errors, IO exceptions, or random timeouts when Niagara tries to send an SMS.

The confusing bit is that SMS still works perfectly from the Teltonika WebUI, so at first glance everything looks fine. In reality, the newer firmware just doesn’t behave the way our driver expects. Rolling the modem back to a known‑good 00.07.14‑series firmware restores normal operation.

”It’s not a long‑term fix - it’s a temporary workaround”
We’re already engaging with Teltonika to understand their upcoming firmware roadmap so we can build a proper, future‑proof solution that aligns with their changes rather than fighting them.

So you cant wait for a fix and need an SMS modem now

If you follow the downgrade steps and load a known‑good 00.07.14‑series firmware onto the Teltonika modem, the Forest Rock SMS Driver will work exactly as expected again. The older firmware restores the AT‑command behaviour our driver relies on, meaning SMS delivery from Niagara becomes reliable immediately after the downgrade.

1. Why Firmware Downgrade Is Needed

Some newer Teltonika firmware versions change how the modem handles SMS and AT commands.
The Forest Rock SMS Driver expects the older behaviour.

Typical issues caused by new firmware:

  • Niagara SMS fails but modem WebUI SMS works.

  • HTTP 4xx errors (e.g. 422) when sending SMS.

  • IO exceptions, timeouts, or “Unable to reach modem”.

  • SMS works only when sent directly from the modem.

Temporary Fix:
Downgrade the modem to a known‑good 00.07.x firmware for that exact model.

2. Before You Start

Confirm the issue matches this pattern:

✔ Hardware

  • Teltonika RUT241 / RUT9xx / TRB500

  • Using modem as SMS gateway for Niagara.

✔ Modem works locally

  • SMS sends successfully from Teltonika WebUI.

✔ Niagara path fails

  • Niagara cannot send SMS OR throws HTTP 422 / IO errors.

✔ Network OK

  • Ping from Niagara → modem works.

  • SIM has credit.

  • Signal is good.

If all checks are positive → firmware regression is the likely cause.

3. Gather Device Information

Log in to modem WebUI → Status → Device

Record:

  • Device model: e.g. RUT241, RUT956, TRB500

  • Firmware version:
    e.g. RUT2M_R_00.07.xx.x, TRB5_R_00.07.xx.x

  • For TRB500: note modem module firmware
    (e.g. RG501QEUAAR12A11M4G_04.200.04.200)

If the customer or RMS recently upgraded the firmware → high confidence cause.

4. Choose a Compatible Firmware Version

Rules:

  1. Must match the exact model

    • RUT241 firmware does not work on RUT9xx

    • Wrong model → “Wrong image” error

  2. Choose a stable earlier 00.07.x release

    • One known to work with Forest Rock SMS driver

    • Avoid the newest builds until the new driver is released

  3. Download from Teltonika support

    • Ensure file ends in .bin

    • Confirm device family matches (RUT2M, RUT9M, TRB5)

If unsure: pick the last non-problematic firmware for that model.

5. Back Up Configuration

Before downgrading:

WebUI → System → Backup/Restore

  • Click Backup / Download

  • Save config file to your PC

Optional (recommended):

  • Screenshot APN settings

  • IP address / LAN settings

  • Serial/TCP port settings

  • Firewall/port forwarding rules

6. Disable Automatic Updates

Prevent the modem re-updating after downgrade:

WebUI → System → Firmware / Update

  • Turn off auto‑check and auto‑update

  • If RMS is used → remove from any automatic update group

7. Perform the Downgrade

Step 1: Upload Firmware

WebUI → System → Firmware / Update

  • Click Choose file

  • Select the older .bin firmware

  • Click Upload

If you see:

  • “Wrong image” → firmware does not match model

  • “Invalid firmware” → corrupt or incorrect file

Step 2: Apply & Reboot

  • Confirm upgrade/downgrade

  • Device flashes + reboots (2–5 minutes)

  • Do NOT power cycle during flashing

  • Wait until LEDs return to normal

  • Verify you can ping the modem again

8. Validate Firmware and Restore Config

After reboot:

✔ Check version

WebUI → Status → Device
Ensure downgraded version is shown.

✔ Restore settings (if required)

WebUI → Backup/Restore
Upload backup file
—or—
Reconfigure manually.

✔ Check mobile registration

  • SIM detected

  • Signal present

  • SMS can send from WebUI

9. Test with Niagara / Forest Rock SMS Driver

In Workbench:

  1. Open station

  2. Locate Forest Rock SMS Driver

  3. Confirm:

    • Correct modem IP and port

    • Driver “Service OK”

    • No active faults

Send a test SMS:

  • Use driver’s test action (if available)

  • Or send from SMS Alarm Recipient

Working indicators:

  • No HTTP 422

  • No IO exceptions

  • SMS appears in modem’s SMS log

  • SMS received on handset

  • Alarm routing sends SMS reliably

If intermittent: check signal/network separately.

10. Prevent Future Auto‑Upgrade

After successful fix:

On modem:

  • Keep auto-update disabled

  • Remove from RMS auto-update groups

Documentation:

  • Record the approved “known‑good” firmware

  • Warn customer not to upgrade firmware until Forest Rock issues updated driver

11. Special Notes for TRB500

TRB500 has two firmware layers:

  1. TRB device firmware

  2. Cellular module firmware (Quectel), example:
    RG501QEUAAR12A11M4G_04.200.04.200

Potential problems:

  • Upgrading module firmware alone can break SMS

  • Teltonika often provides module firmware through support only

Fix:

  • Revert both TRB firmware + modem firmware to a previously confirmed working combination.

12. Future Forest Rock Driver Update

Forest Rock is developing an updated SMS driver that:

  • Supports newer Teltonika firmware

  • Removes requirement for firmware downgrade

  • Improves AT command handling compatibility

This guide should be updated once that driver is released.

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