Texas Instruments MSP430FR6047, User Manual, Page: 9 / 19

The "Algorithm Option" determines which algorithm is used. Only the lobe algorithm is currently available for
water metering. A detailed explanation of how this algorithm works can be found in the
Ultrasonic Sensing
Metrology Subsystem Reference Design for Water Flow Measurement design guide .
The "Envelope Crossing Threshold" determines which lobe the AbsToF algorithm will lock onto. Set this
threshold to lock onto the earliest lobe peak that is above the noise. In the example shown in
Figure 4-5 , this
lobe peak corresponds to a threshold of approximately 22%. Additional information regarding the envelope
crossing threshold can be found in the
Optimized ultrasonic sensing metrology reference design for water flow
measurement .
Figure 4-5. Representative Captured Waveform With Interpolation
The “Search Range” parameter is specific to gas algorithms and is not currently used by the “Lobe” algorithm.
"User Param #6" is reserved for future use.
"User Param #10" is reserved for future use.
4.2.3 Conditional Parameters
Modify the following parameters only under specific conditions.
The "ULP Bias Delay" determines when the bias circuit is turned on. The relevant timing diagrams for the
operation of the ULP bias circuit can be found in the
MSP430FR58xx, MSP430FR59xx, and MSP430FR6xx
Family User's Guide . For low current consumption, the recommended value is 3.
The “Start PPG Count” determines when the PPG is started. The timing diagrams for the operation of the ULP
bias circuit can be found in the
MSP430FR58xx, MSP430FR59xx, and MSP430FR6xx Family User's Guide . For
low current consumption, the recommended value is 10000 nanoseconds. The only scenario in which this value
should be changed is when the time of flight between transducers is less than 30 µs. Use a corresponding
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SLAU810B – SEPTEMBER 2019 – REVISED SEPTEMBER 2020
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