User's Manual

www.lairdtech.com

Laird Technologies

BTM510/511

Bluetooth

Multimedia Module

5. ATO {Enter Data Mode} (letter ‘o’)

Return to data mode. Assume that the module is in data mode after OK is received. Responds with

an error if there is no Bluetooth SSO connection.

Response:

<cr,lf> CONNECT 123456789012,<<cr,lf> (if it was an incoming connection)

<cr,lf> CONNECT 123456789012,><cr,lf> (if it was an outgoing connection)

Response: <cr,lf>ERROR nn<cr,lf>

6. Dropping SSO Connections

In a conventional telephony modem, a call is normally terminated by rst sending a +++ character

sequence enveloped by an escape sequence guard time (of the order of 100 to 1000 milliseconds)

to enter local command and connected mode and then the ATH command.

Laird Technologies BTM devices provide a variety of ways of dropping a connection. One method is

similar to the above, but instead a ^^^ character sequence is used. This is to eliminate ambiguity when

a data call is in progress via a mobile phone which was established using the mobile phone’s Bluetooth

AT modem. The second method involves the host dropping the DTR (DSR from the module’s viewpoint)

handshaking line.

Being able to drop a connection using the escape sequence ^^^ has a severe penalty on data

throughput. In fact, the data rate is of the order of 85kbps instead of about 300kbps. To cater for

this performance hit, the device’s connection drop capability is congurable to be in one of two modes.

One mode allows for a connection to be dropped using either method, and the other mode allows for

a connection drop using the DTR method only. By default, the device is in the former mode. This mode

is selected using the S507 register (Appendix, Table 4.1).

To reiterate, the escape sequence is as follows:-

This means that even when a le transfer is occurring and it happens to be full of <Esc Chr> characters

then it is not going to drop into command mode because, when transferring, a le it is going to happen

as fast as possible and so the inter character gap is going to be signicantly shorter than the <Guard time>.

The <Esc Chr> character can be changed via the S2 register and the <Guard time> interval can be

specied via the S12 register (Appendix, Table 4.1).

7. SSO - Asynchronous Messages

RX<string>

This response is sent to the host when the unit is in online-command mode and S Register 531 is set

to 3 and data arrives from a peer.

If the data from the string contains non-visual characters (for example ASCII 0 to 31 and ASCII 128

to 255), then those characters are translated into a three character escape sequence starting with ‘\’.

For example the embedded <cr><lf> sequence would be sent as the six character string \0D\0A.

If the data contains the character ‘“’ then it is sent as \22.

If the data contains the character ‘\’ then it is sent as \5C.

AT COMMAND SET

REFERENCE