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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specific intervals, and sleeps in very low power mode (around 2ma) otherwise. The power savings can be
quite dramatic.
To enable it, use the “SW,<hex word>“ command.
Example interval timers:
0x0020 = 20ms. (32 decimal * .625 = 20).
0x0050 = 50ms, 0x00A0 = 100ms, 0x0190 = ¼ second, 0x0320 = ½ second, 0x0640 = 1 second.
Sniff mode only pertains to an active connection. When a connection is made, both master and slave must
support Sniff mode, and agree to the Sniff window, otherwise the radio will stay in full active on mode.
Note: the maximum allowed Sniff interval is about 20 seconds = 0x7FFF sniff word setting.
5.3 Enabling Deep Sleep
Deep Sleep mode can be used to obtain extremely low power operation. The device totally shuts down and
only draws about 300uA of current in this mode. To enable Deep Sleep, set the high order bit of the Sniff
word = 0x8000. This bit is NOT used to determine the sleep interval, it is only used as a flag to enable deep
sleep. For example, If you want ½ second sleep 0x0320, with Deep sleep, you would set the sniff word to
0x8320.
In normal low power sleep (not deep sleep) the firmware is still running in idle mode, and wakes up about 20
times per second to check ports, update Leds etc. During Deep sleep, the firmware actually stops running
some tasks. For example, the LEDs only update about once per second.
There are 3 ways to wake the radio from sleep mode. The first is to send a character to the UART.
Transitions on the RX pin will wake the device from sleep. Wake time is worst case 5ms. Because of this,
the first character sent is generally lost by the radio. A better way to wake the radio is to toggle the CTS line
from LOW to HIGH,
Wait 5ms, and then send data. The third way is automatic, the radio will wake every <hex word> slot times
(1 slot time = 625us) as defined above. The radio wakes and listens to see if the other side of the connection
has anything to send. This wake time is typically about 5ms (8 slots) even if no data is to be transferred.
Once the radio is awake it will stay active for exactly 1 second of inactivity, and then sleep again.
NOTE: setting this mode can cause latency issues, and dropped bytes/loss of performance in cases where
large amounts of data are being transferred. The nuances of Bluetooth Sniff can be complex, contact Roving
Networks if necessary for more details on how to utilize Sniff mode.
To enable even lower power utilization, use the S|, <hex word> command to set an on/off duty cycle.
5.4 Disabling Output Drivers
Use the command “ S%,1000” to set all PIO0-11 to inputs.
This will also turn off the LED (PIO5) on the FireFly adapter.
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