SerialModem

Simple interface for Serial Modems. Tested:

• Huawei E303 in serial mode

Installation

Add this line to your application's Gemfile:

gem 'SerialModem'

And then execute:

$ bundle

Or install it yourself as:

$ gem install SerialModem

Usage

Simple

If everything is connected and the modem is recognized (/dev/ttyUSB* is available), then you can simply do:

require 'serialmodem'

SerialModem::setup_modem
return unless SerialModem.attached?

SerialModem::ussd_send('*100#')
SerialModem::sms_send('+23599999999', 'Hello from SerialModem')

Ussd

Huawei-modems with Hilink don't support USSD, so you have to switch them to serial-mode. Older modems (pre-2015) are handled with HilinkModem, newer versions not yet. Once the modem is in serial-mode, you can send and receive USSD-codes. It is even possible to use USSD-menus.

Sending

Supposing the modem is setup, you can do

SerialModem::send_ussd('*100#')

Or, if you need a menu where each step needs an answer, you can do

SerialModem::send_ussd('*800#', '1', '2', '1234')

Now each command waits for the last command to be completed.

Receiving

The received codes are stored in an array of hashes, where each hash has three fields:

• time: a string of "%H:%M"
• code: the ussd-code as sent out by 'ussd_send'
• result

There is a maximum of SerialModem::serial_ussd_results_max messages stored.

SerialModem::send_ussd('*128#')
sleep 10
result = SerialModem.serial_ussd_results.first.result

Asynchronous receiving

You can also define a listener in SerialModem.serial_ussd_new

SMS

Similar to USSD, you can send and receive SMS. Due to some restrictions in Huawei-modems, there is a thread that checks for new SMSs every 20s. Normally modems should reply as soon as an SMS is received, but most of the Huawei-modems tested delete SMS automatically when in this mode. If you prefer nonethelss to rely on this mode, set SerialModem.serial_sms_autoscan to 0.

Sending

If everything is recognized, simply do:

SerialModem.sms_send('+23599999999', 'Hello from SerialModem')

And the message should be sent.

Receiving

All SMS are put in a hash of arrays with the key of the hash being the message-id and the elements of the array as follows:

0: sms-flag 1: number of sender 2: unknown field 3: date and time of SMS 4: the message

Asynchronous receiving

You can also use the SerialModem.serial_sms_new variable to set up an automatic callback whenever a new SMS is received:

def treat_sms(list, id)
  p "Received SMS from #{list[id][1]}"
end

SerialModem.serial_sms_new.push(Proc.new { |list, id| treat_sms(list, id) })

# Wait for SMS

Special

Some care has been taken that the serial modem is recognized and can be functional again in case of error:

detach and re-attach in case of power-failure

It can happen that the modem is in use and is reattached because of errors in the power. In that case it is not attached anymore to '/dev/ttyUSB2', but to '/dev/ttyUSB3'. With some luck, the SerialModem.reload_option can help to make things OK again.