Cellular SMS Gateway

v1.0

The Cellular SMS Gateway driver provides bidirectional SMS messaging between an RTI XP processor and a 3GPP-compatible RS-232 cellular modem. It can send queued notifications, insert current RTI system variable values into messages, receive authenticated keyword commands, run dealer-assigned RTI macros, and return optional progress and completion replies to the originating caller.

Validated Hardware and Service

The physically validated configuration used an RTI XP-8v processor, an RTI RJS-232 adapter, and a MultiTech MTC-L4G2D-B01-WW cellular modem containing a Telit LE910C4-WWXD radio. Testing used an active SpeedTalk SMS-capable SIM registered to the STKMOBI LTE network.

The validated serial settings are 115200 baud, 8 data bits, no parity, one stop bit, and no hardware handshaking.

The driver also includes a Generic 3GPP profile for modems implementing the applicable 3GPP TS 27.005 SMS commands and TS 27.007 control commands.

Generic support is standards-based, not a statement that every modem, firmware revision, SIM, or carrier has been tested.

Proprietary serial-to-cloud gateways that do not expose a conventional cellular AT command interface are not supported.

Hardware Preparation and Wiring

1. Install an activated SIM that supports SMS and attach the cellular antenna before powering or initializing the modem.

2. Connect the modem to an RTI RS-232 port using an RTI RJS-232 adapter and standard network cable.

Configuration and Commissioning

Configure the Driver Properties from top to bottom. Resend the RTI project after changing property counts, names, variable selections, or trigger configuration.

1. Under License, enter the processor-bound key when supplied. The driver provides a persistent 30-day evaluation beginning on first use. License Status, Licensed, and License Expired provide commissioning feedback.

2. Under Serial Connection, select the RTI serial port, baud rate, modem profile, and startup delay. Use 115200 baud and Automatic Detection for the validated MultiTech modem.

3. Under SIM and Carrier Configuration, leave Configure APN disabled for ordinary SMS-only service unless the carrier specifically requires an APN. Leave operator selection automatic unless the carrier requires MCC/MNC values. Leave Set SMS Center Number disabled unless the carrier requires a manual SMSC.

4. Under SMS Service, enable outbound SMS, inbound SMS, or both as required. Inbound control is disabled by default.

5. Configure the bounded Outbound SMS Queue. The production defaults are ten active or waiting messages and two seconds between completed SMS transactions.

6. Configure one to ten Saved SMS Destinations using dealer-friendly names and international-format numbers where possible.

7. Optionally configure as many as twenty SMS Variable Templates for cross-driver values and as many as fifty Configured Notifications with recipient preferences.

8. If inbound control is required, configure allowed phone numbers, a strong SMS control password, temporary lockout behavior, and only the keyword triggers that are needed.

9. Under Modem Health and Recovery, retain the default heartbeat and bounded recovery settings during initial commissioning.

10. Temporarily enable TraceViewer logging, initialize the modem, and verify modem identity, SIM Ready status, carrier registration, signal, SMSC, and storage feedback. Disable TraceViewer logging after commissioning because message bodies appear in trace output.

11. Send a test SMS to every required recipient and verify receipt. Then test every authorized inbound keyword, unauthorized sender rejection, incorrect-password behavior, lockout behavior, acknowledgments, progress replies, final completion replies, and processor-reload recovery used by the project.

Modem Profile and Carrier Settings

Automatic Detection selects the MultiTech/Telit profile when the modem identity contains Telit, LE910, MultiTech, or MTC-L4G2. Otherwise the driver uses Generic 3GPP. PAP or CHAP APN authentication uses the Telit AT#PDPAUTH command and therefore requires the MultiTech/Telit profile. APN and optional authentication settings are applied during every initialization, not as a one-time provisioning action.

Saved Destinations and Outbound Messaging

Saved SMS Destinations provide one to ten reusable recipients. Each number must contain 3 through 20 digits with only an optional leading plus sign.

A command stores the stable destination slot, so changing a slot's name or number changes where that command sends without changing the macro assignment. Saved destinations are separate from inbound Allowed Phone Numbers; configure a number in both places when it must send and receive authorized commands.

Send SMS to Saved Destination and Send SMS to Entered Number send literal text. The two Variable Template commands expand selected RTI values immediately before queueing. All outbound paths use the same bounded queue, spacing, license checks, modem readiness checks, counters, feedback, and events.

Queue-full attempts are rejected. Clear Queued Outbound SMS removes only waiting messages and never cancels an active submission that the modem may already have accepted.

Configured Notifications and Recipient Preferences

Each configured notification has a dealer-defined name, a Default Message Template, and one initial/reset delivery checkbox for every configured destination slot. These checkboxes establish defaults only when no persistent runtime preference exists or when a reset command is used. User changes made through Set Notification Preference are saved independently and survive project downloads and processor restarts. Resending programming does not overwrite an established runtime preference.

Send Configured Notification uses the saved Default Message Template. Send Configured Notification with Custom Message uses the same recipient preference group but obtains the message from the macro. Invalid or duplicate enabled numbers are skipped; an all-recipient capacity check prevents capacity-related partial submission. Notification events indicate queue acceptance, not handset delivery.

System-Variable Message Templates

A message can contain {VAR1} through {VAR20} or a configured friendly-name token such as {Alarm Keypad Display}. Configure each source as Boolean, Integer, or String and set Boolean labels, integer divisor, prefix, and suffix as required. Missing values expand to N/A.

Unknown tokens remain visible so configuration errors are not hidden. The driver reads the source value immediately before sending; GUI display formatting is not automatically applied.

Inbound Control Security

Phone-number normalization removes a leading plus sign and common formatting characters but does not remove country-code digits. Configure each allowed number with the same country code reported by the modem. The normalized sender must exactly match an allowed number.

When an SMS Control Password is configured, a command must begin with the exact case-sensitive password followed by a space and the keyword. Keyword matching is exact and case-insensitive after authentication. Generic Macro:: execution is disabled by default and should remain disabled unless the dealer has a documented need and has tested the risk.

Temporary authentication lockout tracks failures independently for each otherwise allowed sender. Unauthorized outside numbers cannot lock an allowed user. During lockout, messages may still be received and logged but cannot execute RTI macros. Clear Inbound Security Lockouts provides a manual reset.

Keyword Triggers, Progress, and Completion Replies

Keyword Trigger Count displays zero through thirty trigger slots. Each trigger has a dealer-facing Name, an exact inbound Keyword, an Enable property, a Macro To Run, and optional completion-reply behavior. The Name appears in command dropdowns; the Keyword remains the SMS text. Reducing the count hides and disables higher slots without erasing their properties.

Send Keyword Trigger Acknowledgments optionally queues <keyword> Received after an authorized exact match is submitted to RTI. This confirms authentication, matching, and macro submission, not completion of every macro action.

For verified completion replies, enable Wait for Macro Completion Reply on the trigger. Use Send Progress Reply to Trigger Sender or Send Variable Reply to Trigger Sender for intermediate messages, then place Reply to Trigger Sender as the final macro action. Select the same Trigger Name in each command.

Progress replies do not release the caller; the final reply does. The macro must complete before Trigger Completion Timeout expires. Requests for the same trigger are serialized while different triggers remain independent.

Startup and Unread-Message Recovery

After every driver or modem initialization, the driver verifies the inbound-notification mode and scans modem storage for unread messages. Each recovered entry is deleted before execution, then its 3GPP service-center timestamp is validated against Recovered SMS Maximum Age. Only fresh, verifiable entries proceed to authentication and trigger matching. This delete-before-execute policy prevents the same physical-control command from being replayed after another restart. Stale, malformed, or unverifiable recovered entries cannot execute.

The initial startup state establishes a baseline and does not manufacture historical SMS, recovery, or security transitions. Operational outbound and trigger queues are held in memory and are cancelled by a driver or processor restart. Modem storage is the authoritative persistent inbound queue.

Notification preferences, the license evaluation timestamp, and the optional last-ten inbound history use RTI persistence.

Modem SMS Storage Maintenance

Refresh SMS Storage Status updates the selected storage, used count, and capacity. Delete Read SMS Only removes messages marked read. Delete All Stored SMS permanently removes every stored message, including unread commands, and should be used only as an explicit maintenance action. These commands are separate from Clear Queued Outbound SMS.

Automatic Recovery

Automatic Recovery is enabled by default. Repeated heartbeat failures or an unregistered LTE state cause bounded serial-session reinitialization after the configured failure threshold. Automatic Recovery does not software-reboot or power-cycle the modem. Recovery variables and events report the current state, consecutive failures, attempt number, completed cycles, and last reason.

MultiTech/Telit Software Reboot and Shutdown

Software Reboot MultiTech/Telit Modem uses AT#ENHRST=1,0 and is available only when the validated profile is active and initialized. It cancels the active modem transaction, clears queued outbound SMS, waits the configured startup delay, and performs complete initialization. Because the modem may restart before returning its final OK, a timeout is not immediately retransmitted; the driver waits and verifies the restart by reinitializing.

Power Down MultiTech/Telit Modem sends AT#SHDN, stops supervision, and waits 30 seconds. Remove power only after the completion event or Modem powered down feedback confirms completion. The modem cannot be restarted through the three-wire serial connection after shutdown; cycle external power, wait for boot, and invoke Initialize Modem.

Diagnostics and Troubleshooting

The driver exposes modem manufacturer, model, firmware, IMEI, SIM ICCID, SIM status, network registration, carrier, radio access, signal strength, SMSC, storage, queue, recovery, reconnect, reboot, security, and message diagnostics. Request Modem Status refreshes changing registration, signal, SIM, SMSC, and storage values. Identity values are refreshed during initialization.

If the modem does not initialize, verify the selected serial port, baud rate, wiring direction, signal ground, antenna, SIM readiness, and AT response in a PC terminal.

If the modem is responsive but not registered, verify carrier activation, antenna placement, supported LTE bands, account status, and automatic operator selection.

If inbound commands do not execute, verify Enable Inbound SMS Control, allowed-number formatting, country code, password capitalization, exact keyword text, trigger Enable, and the assigned RTI system macro.

If a progress or completion reply is rejected, verify Wait for Macro Completion Reply, matching Trigger Name, an active request, outbound SMS enablement, and the completion timeout.

If notifications do not reach a recipient, inspect the persistent preference variable, saved number, queue capacity, modem submission result, carrier service, and recipient route.

Disable TraceViewer logging after testing because inbound and outbound message bodies can appear in logs. APN credentials and the configured SMS control password are redacted, but message content may still be sensitive.

Message and Service Limitations

Outbound SMS is limited to 160 characters. Multipart or concatenated SMS, UCS2/Unicode, MMS, attachments, and carrier delivery reports are not supported. SMS Sent confirms that the modem accepted the submission and returned a message reference followed by OK; it does not confirm handset delivery.

The driver does not retry after sending the message body and Ctrl-Z because the modem may have accepted the message even when the final response was lost. This avoids duplicate messages.

Version History

Version 1.0 - Initial release.

Developed & Supported By

Buttonwood Technologies, LLC

rti@buttonwoodtechnologies.com

https://www.buttonwoodtechnologies.com

Product Specific Warning

SMS delivery is not guaranteed and can be delayed, duplicated, reordered, filtered, rejected, or lost because of modem state, signal quality, carrier service, account status, recipient service, message length, or network congestion. Incoming SMS automation must use restrictive sender authorization and command validation, but telephone-number identity is not equivalent to strong cryptographic authentication. Do not use this driver as the sole path for emergency, fire, medical, security, or life-safety notification or control. The dealer must test the installed modem, SIM, antenna, carrier, recipient routes, restart behavior, queue limits, authorization rules, and an independent fallback notification method.

Third-Party Driver Notice and Disclaimer

This driver is independently developed by Buttonwood Technologies, LLC and is not developed, endorsed, supported, or certified by the manufacturers or service providers with which it interoperates, unless expressly stated otherwise. The driver is provided “AS IS” and “WITH ALL FAULTS,” without warranties of any kind, express or implied, including warranties of merchantability, fitness for a particular purpose, and noninfringement. To the maximum extent permitted by applicable law, Buttonwood Technologies, LLC shall not be liable for indirect, incidental, special, consequential, exemplary, or punitive damages, loss of data, loss of use, service interruption, or lost profits arising from installation or use of the driver. Nothing in this notice excludes or limits liability that cannot lawfully be excluded or limited