Enhanced Class 1 Bluetooth v2.1 Module
Hardware Integration Guide
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www.lairdtech.com/bluetooth
13
CONN-HIG-BT740
5
F
UNCTIONAL
D
ESCRIPTION
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 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.
5.1
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 of the required S-register in the Firmware User manual), 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
BT740
UART_TX
UART_RX
UART_CTS
UART_RTS
UART_DSR
UART_DTR
UART_RI
UART_DCD
Application - Host
/RXD
/TXD
/RTS
/CTS
/DTR
/DSR
/RING
/DCD
