Enhanced Class 1 Bluetooth v2.1 Module
Hardware Integration Guide
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www.lairdtech.com/bluetooth
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CONN-HIG-BT740
Power Supply Consideration – The power supply for the module should be a single voltage source
of VCC within the VCC_IN range of 3.3 V to 5.0 V. It must be able to provide sufficient current in
a transmit burst. This can rise to 200 mA. To limit dissipation it is recommended that you use a
voltage at the lower end of the range.
The module includes regulators to provide internal local 3.3 V. This rail is accessible on pin 13 for
monitoring purposes only. Under no circumstances should this pin be used to source current.
Pins 7, 8, 9 and 10 (PCM related) are NOT supported in Firmware therefore are NC (No Connect)
pins.
Add a 10 k pull-up to the host PCB on the UART_RX, otherwise the module will remain in deep
sleep if not driven to high. Add a 10 k pull-down to the host PCB on the UART_CTS that if it is not
connected (which we do not recommend) then the default state for UART_CTS input will be
asserted which means can send data out of UART_TX line.
GPIO lines can be configured through software to be either inputs or outputs with weak or strong
pull-ups or pull-downs. At reset, all GPIO lines are configured as inputs with weak pull-downs.
UART_RX, UART_TX, UART_CTS, UART_RTS, UART_RI, UART_DCD, and UART_DSR are 3.3 V level
logic. For example, when RX and TX are 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.
Pin 28 (UART_RI) is active low. It is normally 3.3 V. When a remote device initiates a connection,
this pin goes low. This means that when this pin is converted to RS232 voltage levels it has the
correct voltage level for assertion.
Pin 17 (UART_DCD) is active low. It is normally 3.3 V. When a connection is live, this pin is low.
This means that when this pin is converted to RS232 voltage levels it has the correct voltage level
for assertion.
Pin 16 (UART_DSR) is an input, with active low logic. It should be connected to the DTR output of
the host. When the BTM740 module is in high speed mode (see S Register (in AT mode) in the
Firmware User manual), this pin should be asserted by the host to ensure that the connection is
maintained. A deassertion means that the connection should be dropped or an online command
mode is being requested.
Pin 13 (VCC_3V3 monitor) may only be used for monitoring purposes. It must not be used as a
current source.
The GPIO pins can be accessed using S Registers in AT mode and a special command in MP mode.
See the Firmware User manual for S-register required.
GPIO3 is also used for DTR output (active low). See the Firmware User manual for S-register
required.
Analogue 0 and 1 should not exceed 1.8 V and see the Firmware User manual for S-register used
to access them.
