Telit GT863 GPRS module

[metanoya]

Hi

Has anyone on this forum ever used a GPRS module to FTP a file from a PIC/DSP to an FTP server? I am using the GT863 from Telit and am running into some problems. When I connect the module to my PC and send it AT commands via hyperterminal, I am able to create a new file on the FTP server and transfer some characters to it. This works fine. As soon as I connect the module to my DSP through RS232, it doesn't work. I am able to establish a GPRS connection and an FTP connection. On the server, it shows that the modem is connected, but I can't transfer files. The files are created on the server with a size of 0 bytes and I can't transfer anything to them, as the GPRS module indicates that the FTP connection doesn't exist.

Can anyone please help me?

Thanks.

 

[Super_voip]

Sounds like a job for WireShark. It looks like the TCP stack on the PIC side may be having problems, the only way to find out what problem is to use a protocol analyzer any other way is guess work.

 

[Diver300]

Do you mean GM863?

I haven't done any FTP with a Telit module, but I have used GPRS.

To see what goes on when the microcontroller is talking to the Telit module, I connect the Tx and Rx lines to diodes and a pull up resistor, and to a MAX232. The output of the MAX232 is connected to a PC, running a terminal emulator which logs the data. Hyperterminal might well work for that.

The Telit module has local echo by default, but that stops as soon as the GPRS connection is open. That is why the diodes are needed, to monitor both the transmit and recieve.

I use the PC monitoring of the Tx ans Rx all the time to see if the microcontroller is doing what I want it to do, and if the Telit module is doing what I think it should be.

I would be interested to know how you do FTP through a Telit module.

 

[metanoya]

FTP through GT863

The GT863 is the same as the GM863, it just includes a nice casing, SIM card holder and GSM antenna. I looked at the output of the modem on a PC and everything seems fine. I establish a connection and receive an 'OK' to indicate that it was successful. When I issue the AT#FTP=? to check the connection, I get 'ERROR' indicating that there is no FTP connection. On the FTP server it shows that the module is indeed connected. Any ideas?

 

[Diver300]

I assume that you are writing the same thing with hyperterminal that you get the microcontroller to write.

If so, and you are getting the error, I suggest that you add some pauses. We were recommended to pause a second or so from each reply before the next command.

Also, I have found that the Telit modules are extreemly sensitive about baud rates. If the edges of any bits are slightly wrongly timed, the module doesn't understand it, although the PC handles the same signal no problem.

The EUSART on the 16 bit PICs has a fault that give a short stop bit , if you send more data as soon as TRMT goes high. I suspect that will upset the Telit modules.

You could look at **broken link removed**

 

[metanoya]

FTP through GT863

I tried the delays, but it doesn't work. Is flow control essential, because I realised that I only connected Tx, Rx and Gnd? Maybe FTP needs flow control? I'll post details on FTPing from a GM863 as soon as I fixed it.

 

[Diver300]

I don't know if FTP needs flow control, but I have found phones that work fine for GSM but stop when using GPRS. I think that was due to the extra noise affecting the flow control lines.

When I turned off hardware flow control with AT&K0<ret> it worked fine.

 

[metanoya]

FTP through GT863

Sorry for being so quiet, but project nearly killed me the last month or so. I actually managed to FTP a JPEG from a DSP to an FTP server with the GT863. Very easy. Open the GPRS connection, connect to the FTP server, set binary mode, specify filename on server, then you need to transfer the file byte-by-byte followed by "+++" when done. There are AT commands to do all of this. My problem was due to a setting on the FTP server that was incorrect. If you need code or anything, just let me know.

 

[rg470]

Need Help on AT Commands to establish FTP Connection!

I am in the middle of an academic project, trying to establish FTP Connection between GPRS modem & Web server to transfer files using AT commands... Would you be able to provide some help regarding this?? I am using microchip microprocessor to send AT commands to a GPRS/GSM modem via RS232. Thanks in advance!!

 

[metanoya]

FTP via GPRS

I haven't looked at these things in a very long time, but I am more than willing to share what I still remember. You can email me directly at

sheunis at gmail dot com

I am in the middle of an academic project, trying to establish FTP Connection between GPRS modem & Web server to transfer files using AT commands... Would you be able to provide some help regarding this?? I am using microchip microprocessor to send AT commands to a GPRS/GSM modem via RS232. Thanks in advance!!