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Range-finding in an awakening period takes about 12ms, and awaiting users’
read-operation consumes about 42.2mW. Assuming it waits for 5ms, based on the
information, it consumes on average 4.1mW if we wake it up every one second, and on
average 1.76mW if we wake it up every ten seconds.
6.11.3 Caveats
Users should not send any setup command in the Ultra-low Power Mode, because MCU will be in
sleep so that it may not respond to users’ command. In Ultra-low Power Mode, it is only allowed to
bring up range-finding, or to turn off the mode. All other operations should be performed after the
mode is turned off.
6.12 Single Frequency Mode
TF-Luna obtains distance measurement from phase shift of the sinusoidal modulated laser light.
The model is subjected to the “periodic distance” problem. The periodic distance for TF-Luna is 15
meters, when working in Single Frequency Mode. However, when the distance is beyond 15 meters, the
measured value starts from zero again. Assuming there is a highly reflective object at 16 meters;
TF-Luna may mistake it as at 1 meter. In order to extend the periodic distance, TF-Luna sets the default
work mode to Dual Frequency Mode. The periodic distance in such a mode is over 65 meters, far wider
than the sensor’s measuring range. In this way, the “overshoot” problem is addressed.
However, in Dual Frequency Mode, the range-finding algorithm requires higher stability on sensor
data. When the signal is weak (AMP lower than 100), the low data stability produces errors in the range
algorithm, and thus yields anomalies in output range values. The error can reach tens of meters. In
some application scenarios, the target reflection rate is low so that AMPs lower than 100 are needed. In
this case, users can set TF-Luna to Single Frequency Mode. In Single Frequency Mode, when AMP is
lower than 100, the stability of range data is low. Even so, it is not allowed to have significant anomalies
on data values. Meanwhile, users should make sure their application scenarios are not subjected to the
overshoot problems.
6.13 Additional notes
Please check Appendix II Serial communication protocol for more options, such as version ID
report, system software restore, baud rate configuration, etc.
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