Steps to install and configure minicom on a Raspberry Pi

Steps to install and configure minicom on a Raspberry Pi:

~~~~~
sudo apt-get install minicom lsof

On the Raspberry Pi, USB modems are usually assigned a device name of `/dev/ttyACM0`. To find out for sure, type the following:

dmesg | fgrep ACM

You should get back something like this:

[ 8.366672] cdc_acm 1-1.2:1.0: ttyACM0: USB ACM device

Next, use `lsof` to check if there are any other processes that might have the modem device open. Substitute the correct tty device from the step above.

sudo lsof /dev/ttyACM0

There should be no output, which means there is no other process using the modem.

Now start up `minicom` in setup mode:

sudo minicom -s

You'll see the following screen:

+-----[configuration]------+
| Filenames and paths |
| File transfer protocols |
| Serial port setup |
| Modem and dialing |
| Screen and keyboard |
| Save setup as dfl |
| Save setup as.. |
| Exit |
| Exit from Minicom |
+--------------------------+

Using the arrow keys on your keyboard, highlight `Serial port setup` and hit ENTER. You'll see:

+-----------------------------------------------------------------------+
| A - Serial Device : /dev/modem |
| B - Lockfile Location : /var/lock |
| C - Callin Program : |
| D - Callout Program : |
| E - Bps/Par/Bits : 115200 8N1 |
| F - Hardware Flow Control : Yes |
| G - Software Flow Control : No |
| |
| Change which setting? |
+-----------------------------------------------------------------------+

Only `Serial Device` needs to be changed. 

Press the letter `a`. The cursor will be positioned after the `/dev/modem`. Hit backspace to delete `modem` and then type `ttyACM0`. It should read `/dev/ttyACM0` when you're done. Hit ENTER.

Hit ENTER again to get back to the `[configuration]` menu.

Using the arrow keys, highlight `Save setup as dfl` (default). The screen should say, `Configuration saved`.

Highlight `Exit from Minicom` and hit ENTER.

Minicom is now configured.

When you are ready to troubleshoot, type:

sudo minicom

The screen will look something like this:

Welcome to minicom 2.6.1

OPTIONS: I18n
Compiled on Apr 28 2012, 19:24:31.
Port /dev/ttyACM0

Press CTRL-A Z for help on special keys
~~~~

You can now send commands directly to the modem. Type AT and the modem should respond with OK.

How you proceed now will depend on what the problem is you are trying to resolve. You will most likely be obtaining advice from someone in this forum.

As a simple test, call yourself. The modem should respond with RING lines.