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AT commands for the K750i

Once you have established a connection between your computer and your cellphone - either via Bluetooth or the USB cable - you can do some nifty stuff with it: You can retrieve data from the phone, trigger telephony functions, or create new menu items that send information back to your computer.

Content

Since there is a vast number of commands available for the modem interface of the phone, it is quite hard to pick the most interesting ones out of the extensive official documentation. This page tries to show some highlights of this interface, but don't expect a complete reference - If you need such, try the Sony Ericsson documents.

I also developed a C# class library named DisGUISE for these functions, which makes it easy to create applications using the phone as in- and ouput device.

Retrieving phone information

General device information

The most basic data can be gathered by using the ATI (I for information) command: Without additionals data (or with 0 appended), it just displays the phone model:

ATI0
Sony Ericsson K750

OK

Other numbers reveal different data, such as the software revision.

Power state

The command AT+CBC displays the current power state of the cellphone: It basically returns two numbers, the first one indicates whether the phone is connected to AC power or not, while the later reports the charging level of the battery.

Dialing Control

Of course the most basic task for a modem can be performed as well: Dialing a phone number is done with the command ATD, certain flags such as ATDT for tone dialing are supported, but have - since we are dealing with a mobile phone network - no real effect.

You might notice that a command like ATD0123456 produces the error message NO CARRIER: To be succesfull, a semicolon has to be appended to the phone number to be dialed.

Media Player

A running media player can be controlled by the AT command AT*SEMP:

parameter action
0 stop
1 play
2 pause
3 FF start/stop
4 REW start/stop
5 next
6 previous
8 random play mode
10 loop

So AT*SEMP=1 will start the playback of the running media player.

Key Presses

It is possible to emulate key events through two different commands: The older method is AT+CKPD, which takes a sequence of characters and simulates the pressing this key sequence.

The more recent one involves the command AT*EKEY: This command evokes one or multiple key events, and indicates whether the key has been pressed or released.

[more to come]

UI Control

One of the most interesting aspects of the modem interface is the creation and manipulation of user interfaces. With special commands, the phone establishs a user interface that sends its events back to the computer it is linked to. The main intention behind this technique is to enable extension hardware to interact with the user. The protocol employed is relatively easy and well documented, so it should be possible to program a custom microcontroller to use homebrew hardware with the phone.

Creating special menu items

The easiest aspect of hooking into the user interface of the phone is the creation of a custom menu item; This entry can be placed into various locations.

AT*SEAM="Foobar"
*SEAM: 4401

OK

This command adds a menu item labeled Foobar to the accessory menu of the phone (SettingsConnectivityAccessories (On german phones: OptionenVerbindungenZubehör). The number returned by the command is a reference ID to this item: Whenever the menu item is triggered by the user, a message containing this ID number is sent through the serial link:

*SEAAI: 4401

Those messages are called unsolicited result codes, since they are not the direct effect of an AT command, but of a user interaction with the phone. SEAAI specifically refers to a selected menu item, other events are indicated by different message codes.

The location of the menu item is not limited to the accessory menu: Using a second parameter, the new item can be placed at a different location: AT*SEAM="Foobar",2 will move the Foobar item to the Bluetooth menu.

For the menu of the K750i differs from those of other Sony Ericsson phones, the real effects partialy differ from the documentation - The following categories are recognized by the cellphone:

ID Description Location on K750i
0 Connectivity (directly)
1 Bluetooth
2 Entertainment
3 Messaging
4 Organizer
5 Settings - General
6 Settings - Sounds and alarms
7 Settings - Display
8 Settings - Calls
9 Multimedia Entertainment
10 Imaging Entertainment
11 Phonebook ?
12 Applications
13 Accessories (default)

For each accessory device connected, only a single menu item may exist: Once a new entry is created, the old one is removed automatically, as well as when the connection is terminated.

[to be continued, this is great stuff]