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Texting in a GPRS connection

JPRodrigues Nov 27, 2017 08:39 AM

Hi there

Im having a problem that i would like to know if any of you encountered before

I have a water/weather monitoring network (14 stations) that have to send warnings to 6 diferent people every time that the systems find a problem. Initiatly i had this system in GSM, but because of the costs i had to change it to GPRS comunication.

My problem: initialy i tested, sending sms texting in gprs mode. For my amazement the 1st few tests were a sucess, and the sms's seemed to be going out.

I deployed my program on my systems and now it seems that it stoped working this way.

I manage to put it to work another way: every time i want to send text messages i open the COM port, i run my script and after, i close the COM port. But still i have an issue: i have to send a "fake" message before i send th real ones.

My questions:

- Does anyone knows if there is a way to send txt messages using GPRS (im using a Cinterion modem, with at commands)?

- Not using only GPRS and setting up the com port, does anyone knows how not to send the "fake" message? (i tryed with delays but it doesnt seem to work!)

(In my network, im using CR800 and Cinterion modem's)

Best Regards

JDavis Nov 27, 2017 09:02 AM

I think it is an issue with that model of modem. I used AT commands with a Raven XT modem to send SMS commands, and I never had to resend the message.

JPRodrigues Nov 27, 2017 09:19 AM

Hi there

"resend the message"?

You mean after you Open the COM port you just send the text or you send the text in GPRS?


JDavis Nov 27, 2017 09:37 AM

If your modem is in AT command mode, you should be able to just send it the right AT command to send an SMS message.

In CRBasic, remember to add a carriage return at the end of your AT commands.   "AT+CMGF=1" & CHR(13)

The process is 3 steps; erase the buffer, write message to buffer, and transmit from buffer. There should be an AT command reference available for your modem.

Here is an example sequence I found online. These commands should be standard in all GPRS modems. In the Raven XT modems, they had a special command that allowed a single AT command.


A simple demo of SMS text messaging.
+CMGW: 1

+CMSS: 20


If connected to your datalogger on another port, you can watch the traffic on the com port. This video shows you how:


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