Howdie! I trying to run a GPRS modem on an Arduino. My full stack is Nimbelink's NL-SW-GPRS Modem (containing Telit GE910-QUAD GPRS module) with the Nimbelink Arduino Development Shield on an Arduino UNO R3.

My goal is to connect to an FTP server and upload a file. I am following this guide from Nimbelink and section 3.3 from Telit's user guide.

I am stuck because the AT#FTPOPEN command doesn't seem to ever timeout nor does it return any result (ERROR or OKAY).

Here is the AT commands I am running:

> OK

> +CGREG: 0,1
> OK

> OK

> OK

> OK

> OK

> <My IP Address>
> OK

> OK


Where is the IP address of ftp.earthlink.net which I am just using for testing purposes, but I have tried several others. I have tried with FTP mode 0 (active) and 1 (passive) with no change in behavior.

The AT#FTPOPEN just never returns anything (no ERROR and no OK). I've waited up to 5 minutes. The command does returns "ERROR" if I deliberately mess up the syntax of the command (eg. AT#FTPOPEN="") but for any valid format it just seems to hang.

Is this a known problem or something I can easy work around? Am I doing something crazy with my timeout values? Is there an easy way to test the context that I activated with the SGACT?

This is more of a question for an M2M forum, but I'm on an Arduino and it seems like there are many people using GSM modules on Arduino - so I thought I'd post here because I am a bit desperate. Thanks :)

  • The example in the guide uses the URL and port number like this "ftp.earthlink.net:21". Try that instead of the IP address. Commented Jul 26, 2016 at 6:27

1 Answer 1


The issues were:

  1. Pin 9 MSM_nRESET should be explicitly set to HIGH.
  2. Pin 10 (DTR) and pin 11 (RTS) should be explicitly set to LOW.
  3. The Nimbelink device requires 5V external power. With USB power, the modem can intermittently reset during period of high activity. If the modem resets, then the command can appear to run forever when nothing is actually running.
  4. Must use FTPOPEN with connection type 1 (passive).

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