Configuring CP 1242-7 GPRS V2 SMS with S7-1200 in TIA V15

1. Overview

The Siemens CP 1242-7 GPRS V2 (article number 6GK7242-7KX31-0XE0) extends the S7-1200 family with GSM/GPRS connectivity. In addition to IP-based telecontrol, the V2 firmware exposes a SMS signaling and switching channel that lets a station send operator alarms to mobile handsets and accept command SMS replies to drive Boolean outputs. The functionality is delivered as a reusable code library on top of TIA Portal and is documented in the Siemens application example, entry ID 58638283, titled "Signaling and Switching via SMS with S7-1200 and CP 1242-7 V2". The reference PDF is hosted on the Siemens Industry Online Support portal: 58638283_S7_1200_SMS_DOC_V13_en.pdf. The same entry page (which also serves as the download portal for the global library) is available at Siemens Support Entry 58638283.

This article closes the two most common gaps that prevent a first-time user from getting an SMS out of the box:

1. The SMS blocks are not bundled with TIA Portal; they live inside a downloadable global library (.zal file) shipped with entry 58638283.
2. The reference project is published under complete protection, which prompts for a user name and password when you open it. The protection credentials and the function block API are listed on page 56 of the documentation PDF.

The procedures below target TIA Portal V15 with STEP 7 V15, but the same library works with V13 SP1 through V17 as long as the project is recompiled under the active version.

2. Prerequisites

3. Hardware Identification: V1 vs. V2

The CP 1242-7 line has two firmware generations. Only the V2 generation ships the SMS blocks.

Before proceeding, confirm the module label. If the label reads 6GK7242-7KX30-0XE0, the SMS blocks will compile but fail at runtime because the V1 firmware does not expose the underlying CFB blocks SEND_SMS / RECEIVE_SMS over the internal bus.

4. Mechanical Setup and SIM Insertion

1. Power down the S7-1200 rack.
2. Snap the CP 1242-7 onto the leftmost free slot of the CPU (left of the CPU, right of any existing CPs).
3. Insert the SIM card into the spring-loaded slot behind the small door on the front of the CP. The contact surface faces the front of the module, the cut corner points outward.
4. Connect the GSM antenna to the SMA connector and route the cable away from the CPU's 24 V wiring.
5. Power up the station. The STATUS LED should pulse green within a few seconds; the CONNECT LED remains off until the configuration has been downloaded.

5. SIM and APN Parameters

The CP must know how to attach to the GSM network even when only SMS is used, because subscriber authentication runs over the same cellular control plane.

6. TIA Portal Project Structure

1. Open TIA Portal V15 and create a new project: Project → New… with a meaningful name, for example CP1242_SMS_Demo.
2. Insert an S7-1200 station: Add new device → Controllers → SIMATIC S7-1200 → CPU → your CPU (for example, CPU 1217C DC/DC/DC, 6ES7217-1AG40-0XB0).
3. Open Device configuration on the CPU. The CP 1242-7 must be dragged from the hardware catalogue (Communication → CP 1242-7) onto the left slot of the CPU. The catalogue entry must read V2 (not V1).
4. Save and compile the device configuration. The CP now appears as CP 1242-7_1 in the project tree.

7. CP 1242-7 V2 Configuration

Select the CP in the device view and configure the following tabs:

7.1 Ethernet addresses

Leave the IP address set to 0.0.0.0 if the station is purely SMS-driven. If you also intend to do telecontrol, assign a fixed IP and subnet mask that matches the LAN the CPU is on.

7.2 Mobile network

• APN: enter per Section 5.
• User name / Password: as supplied by the operator.
• Dial-in number: *99***1#.
• SMSC address: leave blank for automatic, or enter the explicit center number.
• PIN: enter if the SIM requires one.

7.3 Time-of-day synchronisation (optional)

If the CPU clock must be synchronised via the cellular network, enable Synchronisation and select the NTP server of the mobile operator. SMS does not depend on this setting.

8. Importing the SMS Global Library

The library is not part of the TIA Portal installation. It is downloaded as a zipped archive from Siemens Support under entry 58638283.

1. Go to Siemens Support Entry 58638283 and download the ZIP archive that contains the global library (.zal file) and the documentation PDF.
2. Extract the ZIP to a working folder. Locate the file CP1242-7_SMS_Vxx.zal.
3. In TIA Portal, open the Libraries task card (right side of the workbench).
4. Click the small icon "Open global library" in the toolbar of the Libraries task card.
5. Navigate to the extracted .zal file and confirm. The library appears under Global libraries.
6. Expand the library. You will find the master copies:
   • CP1242_SMS (FB) — high-level wrapper used by the example program
   • SndSms (FB) — send one SMS
   • RcvSms (FB) — poll incoming SMS
   • Associated data block types and a UDT for phone numbers
7. Drag SndSms and RcvSms from Master copies into a new Program blocks folder of your CPU to instantiate them. TIA Portal will auto-generate instance DBs (SndSms_DB, RcvSms_DB).

9. Resolving the Password Prompt

The example project shipped with the entry is protected against accidental editing. When you try to open the project, TIA Portal will ask for a User type, User name and Password. Three resolutions exist:

1. Read the documentation, page 56. The project protection credentials, the block interface, and the ladder example are printed there. The credentials change between revisions; always cross-check against the PDF revision that ships with the library you downloaded.
2. Create your own copy. Instead of opening the supplied project, create a fresh project (Section 6), then import only the global library (Section 8). The library itself is not write-protected; only the sample project is. You will then build the program from scratch against the unprotected library blocks.
3. Strip the protection in TIA Portal. If you must edit the supplied project and you have the credentials, change the protection under Project tree → right-click project → Properties → Protection, set the protection level to "No protection", recompile, and save.

10. The SndSms Block Interface

11. The RcvSms Block Interface

12. Building the Program (OB1 Skeleton)

The following LAD/ST skeleton wires the two blocks to a 2-Hz clock bit and a Boolean trigger.

Network 1 — RcvSms enable, always on

// RcvSms_DB (EN := TRUE,  PollCyc := T#2s,  NewSms => Tag_NewSms, ...)

Network 2 — SndSms trigger from a rising edge

// SndSms_DB (REQ := "SendTrig",  PhoneNumber := '...',  SmsText := 'Alarm: Tank High');

Network 3 — Acknowledge and parse the incoming command

IF Tag_NewSms THEN
   // compare RcvSms_DB.SmsText against 'PUMP_ON', 'PUMP_OFF', 'STATUS'
   // set corresponding output bits, latch until next command
END_IF;

13. Compile and Download

1. Right-click the CPU in the project tree → Compile → All. Resolve any type conflicts before downloading.
2. Connect the engineering PG to the CPU via PROFINET or PROFIBUS.
3. Right-click the CPU → Download to device → Hardware and software.
4. In the download dialog, tick "Include SMSC and APN parameters" if your TIA Portal version prompts for it. This guarantees the mobile network configuration reaches the CP, not only the CPU.
5. After the download, the CP will reset, register on the GSM network and attempt to attach to the GPRS APN. Registration takes 20-60 seconds on a cold boot.

14. Verification Procedure

1. Open an online watch table on the instance DBs.
2. Force REQ of SndSms_DB to TRUE. Expect BUSY TRUE for 2-5 seconds, then DONE TRUE for one cycle and a non-zero SMS_ID.
3. Check the recipient handset: an SMS with the text configured in SmsText must arrive within 30 seconds. If the operator network is congested, delivery can take up to 5 minutes.
4. Send an SMS from a handset to the SIM number installed in the CP. Within the PollCyc interval, NewSms must pulse TRUE and PhoneNumber/SmsText must populate.
5. From the handset, send the command string (e.g. PUMP_ON). Verify that the corresponding Boolean is set in the CPU.

15. CP 1242-7 V2 LED Diagnostics

16. STATUS Word Error Codes (SndSms / RcvSms)

17. Troubleshooting Matrix

18. Migration Notes

If you are upgrading an existing project from a CP 1242-7 V1 to a V2 module:

• The hardware article number changes from 6GK7242-7KX30-0XE0 to 6GK7242-7KX31-0XE0. The device configuration must be replaced, not patched.
• Any program that uses SEND_SMS/RECEIVE_SMS as native CFBs from the V1 catalogue will disappear after the swap and must be replaced with the SndSms/RcvSms library blocks.
• The TIA Portal project version can stay the same; only the device configuration and the program blocks need re-compilation.

19. Field-Commissioning Checklist

1. Confirm CP part number 6GK7242-7KX31-0XE0 on the label.
2. Verify SIM works in a mobile handset: outgoing SMS, incoming SMS, no PIN prompt.
3. Insert SIM, attach antenna, power up.
4. Download hardware + software to the S7-1200/CP pair.
5. Wait for STATUS solid green (configuration accepted).
6. Force one SndSms in the watch table; confirm DONE=TRUE and handset receives the message.
7. Send a command SMS from a handset; confirm RcvSms populates and the user program reacts.
8. Log the SIGNAL QUALITY LED state and the operator name (visible in the online diagnostics of the CP) for future maintenance.