Rainbow Electronics DAB-WLS-C21 (BlueTooth) - Manual (Page 18)

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DSH_BTM402_0v9 BISM2 PA Data Sheet.DOC © 2007 EZURiO Ltd 18
Notes:
1. DSR is used by the module to sense that the host is connected, and is intricately linked with
connections. For outgoing calls, if this line is not asserted then an error is indicated. Similarly for
AT+BTP and AT+BTG.
While in a call, for appropriate modes, a de-assertion means fall into command state. If the de-
assertion exists for longer than the period specified in S Register 519 then the connection is dropped
as if an ATH command was received.
2. RI, is normally de-asserted. When an incoming connection is detected it will be asserted, until
the connection is either answered or rejected using ATA and ATH respectively. See S Registers 552 &
553 for more details
3. DCD will be de-asserted when the device is in the unconnected state. Asserted when a
connection is active. See S Registers 552 and 553 for more details.
4. PIO3 is either used as GPIO or driven as UART_DTR. When the unit is configured in pure host
mode, this pin is forced into UART_DTR and is asserted when there is a Bluetooth connection.
GPIO Pins 3 to 9 are available for general purpose use.
9.2 Modem signalling over Bluetooth
The RFCOMM protocol used in Bluetooth for implementing the serial port profile allows for the
exchange of four modem signals. This information is contained in a special transparent message
which contains bits identified as RTR, RTC, DV and IC which depending on the type of serial device
being emulated maps to DTR or DSR, RTS, DCD and RI respectively. In addition, this message also
includes the ability to convey a BREAK input from one end to the other.
To allow for the greatest flexibility and variability in how the modem control signals are used out in
the real world, S Registers 551, 552 and 553 have been provided which allow for any of RTR, RTC,
DV and IC to be mapped to any modem control/status line.
BREAK signal on RX line
If the host sends a break signal of duration greater than 100ms, then the module is
configured to treat that as a signal to perform a hardware reset.
For obvious reasons it is not possible to convey a BREAK over Bluetooth to the peer device.
9.3 Pure Cable Replacement Mode
The module has the capability of being preset into a pure 5-wire data cable replacement mode. The 5
wires being RX, TX, CTS, RTS and GND. This mode requires no changes to a host application since
the Bluetooth connection is automatically set up on power up. If the connection is lost the BISM II PA
module will constantly retry until the connection is reinstated.
By implication, two devices are needed to replace a cable. One device is pre-configured to always be
a master and the other, a slave.
Assuming the Bluetooth address of the master to be and that of the slave to be
, the master module is configured by sending it the following AT commands:
AT&F*
ATS512=1
ATS504=1
ATS507=2
ATS530=2000
AT&W
AT+BTR