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how to connect 2 gsm/gprs modem?

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In general you need a hardware interface of some kind to a PC or other "terminal device".

On a PC you would use an appropriate serial modem program to connect to the hardware interface as a serial port. You would then use the Hays/Rockwell modem attention (AT) comands to send the appropriate data to dial and then connect.

Having established the basic serial connection you might need to establish another protocol such as SLIP or PPP over the top of this. If this is the case you will need to have an appropriate "stack" in place to connect.

Before you go any further you need to find out what it is you are trying to do and the parameters of the service you are connecting to by that I mean the actuall destinatin modem you are dialing not the phone network you are connecting to.

If you are not sure I would look at using a Linux box not a windows box to get yourself up and running as the diagnostic tools available and the help on line generaly better.

---------- Post added at 23:04 ---------- Previous post was at 23:01 ----------

In general you need a hardware interface of some kind to a PC or other "terminal device".

On a PC you would use an appropriate serial modem program to connect to the hardware interface as a serial port. You would then use the Hays/Rockwell modem attention (AT) comands to send the appropriate data to dial and then connect.

Having established the basic serial connection you might need to establish another protocol such as SLIP or PPP over the top of this. If this is the case you will need to have an appropriate "stack" in place to connect.

Before you go any further you need to find out what it is you are trying to do and the parameters of the service you are connecting to by that I mean the actuall destinatin modem you are dialing not the phone network you are connecting to.

If you are not sure I would look at using a Linux box not a windows box to get yourself up and running as the diagnostic tools available and the help on line generaly better.
 

lurchman said:
In general you need a hardware interface of some kind to a PC or other "terminal device".

On a PC you would use an appropriate serial modem program to connect to the hardware interface as a serial port. You would then use the Hays/Rockwell modem attention (AT) comands to send the appropriate data to dial and then connect.

Having established the basic serial connection you might need to establish another protocol such as SLIP or PPP over the top of this. If this is the case you will need to have an appropriate "stack" in place to connect.

Before you go any further you need to find out what it is you are trying to do and the parameters of the service you are connecting to by that I mean the actuall destinatin modem you are dialing not the phone network you are connecting to.

If you are not sure I would look at using a Linux box not a windows box to get yourself up and running as the diagnostic tools available and the help on line generaly better.

---------- Post added at 23:04 ---------- Previous post was at 23:01 ----------

In general you need a hardware interface of some kind to a PC or other "terminal device".

On a PC you would use an appropriate serial modem program to connect to the hardware interface as a serial port. You would then use the Hays/Rockwell modem attention (AT) comands to send the appropriate data to dial and then connect.

Having established the basic serial connection you might need to establish another protocol such as SLIP or PPP over the top of this. If this is the case you will need to have an appropriate "stack" in place to connect.

Before you go any further you need to find out what it is you are trying to do and the parameters of the service you are connecting to by that I mean the actuall destinatin modem you are dialing not the phone network you are connecting to.

If you are not sure I would look at using a Linux box not a windows box to get yourself up and running as the diagnostic tools available and the help on line generaly better.
Click to expand...

ok, i have 2 sim data card , one of them are dynamic IP,and the other are static IP
also i have a GSM/GPRS modem telit GE865-quad and it's AT command files in the links below
https://www.telit.com/module/infopool/download.php?id=542
for GPRS commands
https://www.telit.com/module/infopool/download.php?id=573

i have PIC18F4550 microcontroller used for send AT command for the GSM modem and data "transmitter unit "
and i have GSM modem connected to pc ,used for recieve data from the first GSM modem "reciever unit "

already i have the configration of the network like IP, DNS,APN,user name , password ,etc ...
i don't know how to start this data call between the 2 GSM modems
what AT command i need to establish this data call ????
i need some example to establish this data call over GPRS
or some help plz
thanks for your reply
 

what AT command i need to establish this data call ????
i need some example to establish this data call over GPRS
Click to expand...
There are no data calls over GPRS, just TCP socket connections. I noticed, that Telit brings an embedded TCP/IP stack, so TCP connections can be achieved without involving much software overhead. The method is basically described in the GPRS command manual. Firstly, you have to know, what kind of TCP protocol you want to utilize, e.g. FTP, HTTP or a more low level generic port connection.

Please excuse, that I can't give any examples in this regard, because embedded TCP commands are completely vendor specific. Software utilizing it has to be adapted for each modem type. The other method would be to use only basic PPP over GPRS, that's supported by any GPRS modem and run a software PPP and TCP/IP stack on the processor. That's the way, most computers connect through a GPRS modem. It involves a considerable overhead, but may be reasonable, if a ready-to-use TCP/IP stack is available for a particular micro.
 

FvM said:
There are no data calls over GPRS, just TCP socket connections. I noticed, that Telit brings an embedded TCP/IP stack, so TCP connections can be achieved without involving much software overhead. The method is basically described in the GPRS command manual. Firstly, you have to know, what kind of TCP protocol you want to utilize, e.g. FTP, HTTP or a more low level generic port connection.

Please excuse, that I can't give any examples in this regard, because embedded TCP commands are completely vendor specific. Software utilizing it has to be adapted for each modem type. The other method would be to use only basic PPP over GPRS, that's supported by any GPRS modem and run a software PPP and TCP/IP stack on the processor. That's the way, most computers connect through a GPRS modem. It involves a considerable overhead, but may be reasonable, if a ready-to-use TCP/IP stack is available for a particular micro.
Click to expand...

thanks mr.FvM
how i can establish this connection basic" PPP over GPRS"??
see the AT commands of my GSM/GPRS modem and tell from where i should start ????plz
i need point to point connection between those modems
some one told me u can't do this
i think now to define the receiver unit as server .
 

If one has static IP, then from your AT command set you have to program that static IP to the one with the dynamic IP and make this the Master device.

To clarify things:

Master with Dynamic IP----------------Slave with Static IP
In master program Slave IP
Master will send data to Slave whenever it is needed.

HTH
 

thx for your reply
u have an example for this connection ??
what is that AT command to be used ???
 

If you want to establish a data call on GSM and you can actually get a connection to the modems at either end where when you press the enter key you get OK or after typing ATZ then from one of them you need to send ATDT followed by the number of the other phone. And on the terminal connected to that you should see RING or CALL etc.

Have a look at the Wiki page for the Hayes AT command set and the GSM extensions it has a simple example of using it to establish a data setup between two Hayes AT modems,

Hayes command set - Wikipedia, the free encyclopedia
 

I fear, the intention isn't clear yet.

Basically any GSM modem can establish a CSD (circuit switched data) connection. The called party must have a data only or combined voice/data number and will be called by it. The connection has to be payed by the caller (unless covered by a flat rate). The transmission speed is slow, 9.6 or 14.4k maximum.

GPRS data connections go over dedicated access points (APN) offered by the network provider and are usually routed through the internet. Both peers must have internet access enabled by their internet provider and get either a temporary or permanent internet address. Routing of inbound connections is usually restricted with mobile internet connections, it may be e.g. limited to particular ports. If a permanent internet address has been assigned, it will be usually open to inbound connections, otherwise a permanen IP would be useless. An internet connection has to be payed according to volume or connection time (mostly covered by a flat rate) by both peers.

The original poster has been asking for a GPRS connection through APN, but then wanted to establish a "data call". I guess, that a TCP connection is meant, but it's not completely clear.
 
Last edited:

FvM said:
I fear, the intention isn't clear yet.

Basically any GSM modem can establish a CSD (circuit switched data) connection. The called party must have a data only or combined voice/data number and will be called by it. The connection has to be payed by the caller (unless covered by a flat rate). The transmission speed is slow, 9.6 or 14.4k maximum.

GPRS data connections go over dedicated access points (APN) offered by the network provider and are usually routed through the internet. Both peers must have internet access enabled by their internet provider and get either a temporary or permanent internet address. Routing of inbound connections is usually restricted with mobile internet connections, it may be e.g. limited to particular ports. If a permanent internet address has been assigned, it will be usually open to inbound connections, otherwise a permanen IP would be useless. An internet connection has to be payed according to volume or connection time (mostly covered by a flat rate) by both peers.

The original poster has been asking for a GPRS connection through APN, but then wanted to establish a "data call". I guess, that a TCP connection is meant, but it's not completely clear.
Click to expand...

ok friends,thanks for reply
iam talking about a connection over GPRS "GPRS data connections " by using a GSM network"Mobile operator in my country " ,i do not need establish data call on GSM
how i can use GPRS modem to send data to other GPRS modem ??
i have all configruation APN,IP for each sim card
what is the AT command for that ??
or give me some example for establish this connection and send data over it
now clear ??

---------- Post added at 20:10 ---------- Previous post was at 18:59 ----------

block diagram for my project

---------- Post added at 20:19 ---------- Previous post was at 20:10 ----------

 

After setting the GPRS connection parameters with AT+cgdcont, the PPP connection is started with ATD*99.

On the PC server side, Windows (or any OS) will do this for you. On the mobile side, a PPP and TCP/IP stack must implemented on your microcontroller. When both peers are connected to the network, you can establish a TCP socket connection between them.

Instead of implenting a PPP and TCP/IP stack for the microcontroller, the EasyGPRS (embedded TCP stack) of the Telit modem can be used.
 

FvM said:
After setting the GPRS connection parameters with AT+cgdcont, the PPP connection is started with ATD*99.

On the PC server side, Windows (or any OS) will do this for you. On the mobile side, a PPP and TCP/IP stack must implemented on your microcontroller. When both peers are connected to the network, you can establish a TCP socket connection between them.

Instead of implenting a PPP and TCP/IP stack for the microcontroller, the EasyGPRS (embedded TCP stack) of the Telit modem can be used.
Click to expand...

thanks for your reply
i did the first step
by using this at commands below

at
OK
AT+CGDCONT=1,IP,MMS,0.0.0.0,0,0 *Context parameter setting*
OK
AT+CGQMIN=1,0,4,0,1,31 *Minimum Quality of the Service Requested*
OK
AT+CGQREQ=1,0,4,0,1,31 *Requested Quality of the Service*
OK
ATD*99***1# *GPRS context activation and data state entering*
CONNECT

now , is this command true for the first step ??how i can test if the GPRS connection is being processed or not ??
what is the next step for transfer data and how to do this ???
 

The +CQDxxx stuff is optional and not necessarily required. Connect normaly indicates a connection to the APN (GPRS access point). But there are several negotiation steps performed through PPP that may fail. The problem is, that you can't proceed at this point if you don't have a PPP client implemented in your software. An overview, what PPP is can be found here, also linking the basic internet RFCs specifying the protocol Point-to-Point Protocol - Wikipedia, the free encyclopedia.

An example implementation for PIC can be found here https://ww1.microchip.com/downloads/en/AppNotes/00724c.pdf

If you see the complexity of a PPP implementation, I guess you understand why people are interested to have features like EasyGPRS.
 

thanks for your reply
i see it's complex , now what i can do ???
give me an advice ??
 

now what i can do ??? give me an advice ??
Click to expand...
I already gave it in my first post. Try with the embedded TCP stack of the modem, as described in the EasyGPRS manual. As a disadvantage, the software is restricted to Telit modems, but it's small and simple. You can usually test the connection by "hacking" AT commands to a terminal.

On the PC side, the GPRS modem can be be used in a regular remote network connection. Your software interface will be winsock2 or library working upon it.
 
How to Connect Android Device to GPRS Modem via GPRS.

Hi!
Friends Im doing my Final year Project, "Smart home Automation via Android"
so i need to develop an Android app, but i dont know How to Connect Android Device to GPRS Modem via GPRS.
plz help me
 

hi FvM

I want to send MMS from a PC to a mobile i have a GSM modem (GPRS, EDGE, 3G, etc.) connected to the PC,
plaese help me.
i did the first step
by using this at commands below

at
OK
AT+CGDCONT=1,IP,MMS,0.0.0.0,0,0 *Context parameter setting*
OK
AT+CGQMIN=1,0,4,0,1,31 *Minimum Quality of the Service Requested*
OK
AT+CGQREQ=1,0,4,0,1,31 *Requested Quality of the Service*
OK
ATD*99***1# *GPRS context activation and data state entering*
CONNECT

now , what is the next step for transfer MMS and how to do this ???
 

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