Ezurio BISM2 Guide de l'utilisateur télécharger pdf (Page 28)

5. Dropping Connections

In a conventional telephony modem, a call is normally terminated by first 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.

EZURiO Bluetooth modules 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 200kbps. To cater for

this performance hit, the device’s connection drop capability is configurable 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 former mode. This

mode is selected using the S507 register. See S register table described in an earlier section.

To reiterate, the escape sequence is as follows:-

This means that even when a file 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 file it is

going to happen as fast as possible and so the inter character gap is going to be significantly

shorter than the <Guard time>.

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

be specified via the S12 register.

DSH_50003_v1v3 AT Command Reference 28 of 33

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Ezurio BISM2 Guide de l'utilisateur Page 28