GSM modem: SMS problems

  • Check if the PIN is set on the SIM card or if the VIDEO is set to the correct PIN
  • Make sure you have the correct baud rate at which the GSM modem communicates
  • If the GSM modem is located in a room with a lower signal, an SMS message may not be sent even though the vIDE function block does not return any error. We recommend putting a stronger antenna on the GSM modem
  • There may be a problem with RTS / CTS data flow control when returning error state 26 on the "SendSMSTrig" function block - try to switch data flow control off using our tutorial or on via the serial console (eg with PuTTY program)

Full memmory?

While SMS are leaving one SIM card, SMS are not leaving the other (same operator) - sometimes it throws error 47 - full inbox. You need to delete all messages on the SIM card. Proper communication with the GSM modem is visualized by the Tx A Rx LED on the appropriate port to which the modem is connected. If it connects to the modem at the start of RT (LEDs flash) and then no longer communicates with it - then this is probably the mentioned problem. Proper communication with the GSM modem takes place cyclically with a period of the order of seconds.

Unable to send SMS from GSM-BGS5-T2M modem

GSM modem BGS5-T2M (SEA Prague) does not support the command AT^SSMSS=1. This is part of the definition for the Siemens TC35i modem type in the alarm SMS configuration. Therefore, when using this type of modem, it is necessary to select another profile, ie Wavecom or General, which have an initialization sequence


Also note the need to enter the phone number in quotation marks, see "00420731585458".

For RCWare
The above modem does not support the AT^SSMSS (Set Short Message Storage Sequence) command. In the RcWare command definition file for the respective modem (usually the Siemens MC35i is selected), this command is on the last line. nIt is necessary to delete it: Settings - Computer resources - Modem - (select modem type in AT modem initialization commands) - Edit AT - (delete last line) - Save AT - OK - OK - restart RcWare.

The port monitor also helps with diagnostics, in which we can monitor all communication between RcWare and the modem. The port monitor is activated and deactivated by Ctrl-M - be careful, it only works with the licensed program!

Alarm SMS - one alarm for multiple numbers

It is possible to send one alarm to more numbers, but the numbers must be entered in the format + 420… and separated only by a comma ",", without spaces.

So an example:

Alarm SMS - specialties of operators

Please note that operators require a different number format to which the SMS is to be sent:

  • for O2: 00420xxxxxx
  • for T-Mobile: 00420xxxxxx
  • for Vodafone: +420xxxxxx

Another problem with Vodafone prepaid SIMs may be that the new SMS must be activated, which only occurs when the first call is made from it. Unactivated SMS normally log in to the network, but SMS from it cannot be sent.

If the GSM modem is disconnected from the power supply and reconnected, it is no longer able to establish communication with the IPLC, which is still connected to the power supply and the SMS no longer goes. Tested several times on GSM modem Cinterion TC35i and IPLC300.

GSM modem BGS3-T via USB - works

Sending alarm SMS: GSM modem BGS3-T of the company SEA Prague can AT commands via a virtual COM port, which arises when connected via USB. So we avoid installing a USB-COM adapter and a lot of settings. The modem is connected with a USB cable to a computer with RcWare Vision.

The default speed must be 115 kbps!

ER 75i modem

When installing the modem in some locations, it happens that there are problems (between the operator and the siemens ER 75i module) during automatic DNS assignment.

The solution is as follows:
The following command is entered into the Startup Script: echo „nameserver X.X.X.X“> /etc/resolv.conf, where X.X.X.X is one of the offered IP addresses of the DNS server offered by the operator, you will find it in the system log.

ER75i settings for the O2 CZ operator

For a SIM tariff with a public fixed IP address, the GPRS router needs to have the APN set in the GPRS Configuration
APN: internet.open.s.

For T-Mobile, APN is for both private and public fixed IP addresses internet.t-mobile.cz. More info https://www.svetmobilne.cz/jak-nastavit-pripojeni-k-internetu/57.

(Status from 2010)

MC35i modem and special characters

One of the features of this modem is that it cannot send some special characters (e.g. °). So if an alarm SMS is defined in RcWare Vision or in the Touch screen editor for an analogue that measures, for example, temperature and has degrees Celsius as units, then it simply will not be sent with this modem. On the other hand, Siemens MC75 or Wavecom can send it.