User's Manual

Enhanced Class 1 Bluetooth v2.1 Module
User’s Guide
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www.lairdtech.com/wireless
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CONN-GUIDE-BT740_v0.2
4 FUNCTIONAL DESCRIPTION
The BT740 Bluetooth module is a self-contained Bluetooth product and requires only power to implement
full Bluetooth communication. The integrated, high performance antenna, together with the RF and base-
band circuitry provides the Bluetooth wireless link and the UART interface provides a connection to the
host system.
The variety of interfaces and the AT command set allow the BT740 module to be used for a wide number
of long range wireless applications, from simple cable replacement to complex multipoint applications,
where multiple radio links are active at the same time.
The complexity and flexibility of configuration are made simple for the design engineer by the integration
of an extremely comprehensive set of AT commands, supplemented with a range of “S” registers which
are used for non-volatile storage of system parameters.
To provide the widest scope for integration a range of different physical host interfaces are provided.
4.1 UART Interface
UART_TX, UART_RX, UART_RTS, and UART_CTS form a conventional asynchronous serial data port
with handshaking. The interface is designed to operate correctly when connected to other UART devices
such as the 16550A. The signalling levels are nominal 0 V and 3.3 V, and are inverted with respect to the
signalling on an RS232 cable. The interface is programmable over a variety of bitrates: no, even, or odd
parity; stop bit; and hardware flow control. The default condition on power-up is pre-assigned in the
external flash. UART_RTS and UART_CTS implement two-way hardware flow control. UART_RTS is an
output and is active low. UART_CTS is an input and is active low.
These signals operate according to normal industry convention. UART_RX, UART_TX, UART_CTS,
UART_RTS, UART_RI, UART_DCD, and UART_DSR are all 3.3 V level logic. For example, when RX
and TX idle, they sit at 3.3 V. Conversely for handshaking pins CTS, RTS, RI, DCD, and DSR, a 0 V is
treated as an assertion.
By writing different values to the relevant S register the UART_RI can continuously poll to detect incoming
communication. The UART_RI signal serves to indicate incoming calls.
UART_DSR is an active low input. It should connect to the DTR output of the host. When the module runs
in high speed mode (see definition for S Reg 507), this pin should assert by the host to ensure a
connection maintains. A de-assertion means that the connection should be dropped, or an online
command mode is being requested.
The module communicates with the customer application using the following signals:
 Port /TXD of the application sends data to the module’s UART_RX signal line
 Port /RXD of the application receives data from the module’s UART_TX signal line