RN-21-U Roving Networks Inc, RN-21-U Datasheet - Page 16

• Manufacturer Part Number: RN-21-U
• Description: MODULE BLUETOOTH 2.0/EDR CLASS1
• Manufacturer: Roving Networks Inc

Specifications of RN-21-U

• Frequency: 2.4GHz Center
• Data Rate - Maximum: 921kBaud
• Modulation Or Protocol: FHSS
• Applications: Bluetooth v2.0
• Power - Output: 16dBm
• Sensitivity: -86dBm
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Receiving: 60mA
• Current - Transmitting: 100mA
• Data Interface: PCB, Surface Mount
• Memory Size: 8MByte Flash
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

5
5.1 Optimizing Inquiry (Discovery) and Page (Connection) Windows
Power Management
www.rovingnetworks.com
WARNING: GPIO-4 is used by the system to reset stored parameters to factory defaults. If GPIO4 is pulled high on
power-up, and then toggled 3 times, all user settings will return to default values. Therefore this pin should not be used
as an output, and should not be driven high at power-up time (first 1 second of operation).
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:
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”.
S*,0101
S*,0100
S*,0202
809 University Avenue
GPIO-8 driven HIGH.
GPIO-8 driven LOW.
GPIO-9 driven HIGH.
•
Los Gatos, CA 95032
~ 16 ~
•
Tel [phone]
rn-bluetooth-um Version 4.77 1/24/2011
Advanced User Manual
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