User's Manual

Enhanced Class 1 Bluetooth v2.1 Module
User’s Guide
Americas: [phone] Option 2
Europe: [phone]
Hong Kong: [phone]
www.lairdtech.com/wireless
8
CONN-GUIDE-BT740_v0.2
Notes:
Unused pins may have internal connections and must not be connected.
Note 1: Pins 2, 6, 32, and 33 (SPI related) are only for Laird internal production purposes.
Note 2: Pins 34 - 36 are only for uFL connector version of module – BT740-SC
Note 3: Power-on-reset (power cycling and brown out consideration) – The reset circuitry within the
BT740 module incorporates a brown-out detector; this may simplify power supply design. The
BT740 reset line is an active low. Input debounced so must be low for more than 5 ms to cause
a reset. Upon the application of power, the Power On Reset circuit built into the module ensures
that the unit starts correctly. There is no need for an external power reset monitor.
Note 4: Power Supply Consideration – The power supply for the module should be a single voltage
source of VCC within the VCC_IN range of 3.0 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.
Note 5: The module includes regulators to provide 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.
Compatibility Note for Legacy Devices
If Reset compatibility is required with BTM402 and BTM404:
 Reset logic must invert (on the host PCB) by using suitable BJT (MMBT3904) with collector
connected to Reset pin BT730 module pin 5. A fixed 10k Ohm pull-down resistor to ground (BJT
input) ensures that the BT730 module is out of reset for the condition when host has yet to control
the reset line.
 Add a 10 k pull-up to the host PCB on the UART_RX, otherwise the module remains in deep sleep
if not driven to high.
 Add a 10 k pull-down to the host PCB on the UART_CTS. If it is not connected (which we do not
recommend) then the default state for UART_CTS input asserts, meaning that it can send data out
of UART_TX line.
 PIO lines can be configured through software to be either inputs or outputs with weak or strong pull-
ups or pull-downs. At reset, all PIO lines configure as inputs with weak pull-downs.
 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 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 converts 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 converts 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 definition for S Register 507), the
host should assert this pin to ensure that the connection maintains. 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.
 Access the GPIO pins by using S Registers 623 to 629.