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
13
CONN-GUIDE-BT740_v0.2
Note: The serial module output is at 3.3 V CMOS logic levels. Level conversion must be added to
interface with an RS232 level compliant interface.
Some serial implementations link CTS and RTS to remove the need for handshaking. Laird does not
recommend linking CTS and RTS other than for testing and prototyping. If these pins link and the host
sends data at the point that the BT740 deasserts its RTS signal, then there is a significant risk that
internal receive buffers will overflow, leading to an internal processor crash. This also leads to a drop in
connection and may require a power cycle to reset the module. Laird recommends to follow the correct
CTS/RTS handshaking protocol for proper operation.
4.2 SPI Bus
The module is a slave device that uses terminals SPI_MOSI, SPI_MISO, SPI_CLK, and SPI_CSB. This
interface programs firmware updates at the factory. Laird supplies a PC-based utility to allow a firmware
upgrade over the UART port. Laird highly recommends that customers use this method for updating
firmware.
Note: The designer should be aware that no security protection is built into the hardware or firmware
associated with this port, so the terminals should not permanently connect in a PC application.
4.3 PCM Interface
PCM_OUT, PCM_IN, PCM_CLK, and PCM_SYNC carry up to three bi-directional channels of voice data,
each at 8 k samples/s. The format of the PCM samples can be 8-bit A-law, 8-bit μ-law, 13-bit linear, or16-
bit linear. The PCM_CLK and PCM_SYNC terminals can configure as inputs or outputs depending on
whether the module is the master or slave of the PCM interface. Please contact a Laird FAE for further
details.
The module is compatible with the Motorola SSI TM interface and interfaces directly to PCM audio
devices including the following:
4.3.1 Compatible Codec Chips
 OKI 7702 single channel A-law and μ-law CODEC
 Winbond W681360 13 bit linear CODEC
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