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
144
CONN-GUIDE-BT740_v0.2
Figure 13-1: Sniff Mode
13.8.2 UART Host Power Saving Facility
There are circumstances where a CPU driving the module consumes a lot of power and some means are
necessary to reduce that power consumption while the module is in a Bluetooth connection.
To facilitate that, the module has many GPIO pins, and using S Registers 50 to 65, one (and only one)
GPIO pin can configure with the value 13 so that it is an output configuration.
The state of the pin is 0 when the module’s UART transmit buffer is empty and 1 when there is at least
one byte waiting to be transmitted to the UART host.
Hence a workable power saving strategy by the CPU is illustrated in Figure 13-2.