Roving Networks RN-374 Manual do Utilizador descarregar pdf (Página 16)

Advanced User Manual

www.rovingnetworks.com

rn-bluetooth-um Version 4.77 11/21/2009

809 University Avenue • Los Gatos, CA 95032 • Tel (408) 395-6539 • info@RovingNetworks.com

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NOTE: GPIO2 and 5 are driven by the embedded software as outputs, they can be disabled using the direction

command, (to save power, for example) and used as inputs. If set to outputs the software will override any user values.

SETTING GPIO 8-9-10-11

S*,<hexword> = MASK[11..8] VALUE[11..8]

For the upper 4 GPIO, a single word controls the mask and values, and only the lower 4 bits of each byte are used. The

first time this command is used, all 4 GPIO are driven as outputs and remain so until a power cycle. There is no

powerup command for these bits, only the interactive one. Some modules do not offer these GPIO.

Examples:

S*,0101 GPIO-8 driven HIGH.

S*,0100 GPIO-8 driven LOW.

S*,0202 GPIO-9 driven HIGH.

5 Power Management

5.1 Optimizing Inquiry (Discovery) and Page (Connection) Windows

In slave mode there are two timers that can be used to lower power of the radio while idle. When not

connected, the Bluetooth radio is active for a percentage of time listening for other devices. Other devices

can Discovery (inquire) or Connect (page). The amount of time the radio listens is called the window, and

the interval at which the process repeats is called the interval.

The inquiry and page interval is fixed at 0x1000 = 2.56 seconds. The default window is 0x200 (320 ms) or

12.5% duty cycle.

By lowering the window values, power can be saved at the expense of possibly missing an inquiry or page

request. Since the host usually retries automatically many times, the only downside is a delay in discovery or

connection time.

The page scan window can be adjusted using the SJ command. The minimum window for inquiry or page is

0x0012 (11.25ms), this corresponds to about a 0.5% duty cycle.

The inquiry scan window can be adjusted using the SI command. The minimum window for inquiry or page

is 0x0012 (11.25ms), this corresponds to about a 0.5% duty cycle.

Thus, average power can be reduced from more than 20ma to less than 5ma in standard mode, and less than

3ma in Sniff mode.

It is also possible (and desirable for security reasons) to completely disable inquiry. Once a host has found

and installed a device, inquiry is not needed, only page is used to make a connection. To disable inquiry and

still allow connections, set the Inquiry timer to 0 with “SI,0000”.

5.2 SNIFF mode

Sniff mode is another power conservation method utilized by Bluetooth. By default, Sniff mode is disabled,

and the radio is active continuously when connected (about 25-30ma) . In Sniff mode, the radio wakes up at

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