Instructions

5
Measurement Quick Termination Detection
Address Name Description Initial Value
0x04 ACQ_CONFIG_REG Acquisition mode control 0x08
You can enable quick-termination detection by clearing bit 3 in this register.
The device will terminate a distance measurement early if it anticipates that
the signal peak in the correlation record will reach maximum value. This allows
for faster and slightly less accurate operation at strong signal strengths without
sacricing long range performance.
Detection Sensitivity
Address Name Description Initial Value
0x1c THRESHOLD_
BYPASS
Peak detection threshold bypass 0x00
The default valid measurement detection algorithm is based on the peak
value, signal strength, and noise in the correlation record. This can be
overridden to become a simple threshold criterion by setting a non-zero value.
Recommended non-default values are 0x20 for higher sensitivity with more
frequent erroneous measurements, and 0x60 for reduced sensitivity and fewer
erroneous measurements.
Burst Measurements and Free Running Mode
Address Name Description Initial Value
0x04 ACQ_CONFIG_REG Acquisition mode control 0x08
0x11 OUTER_LOOP_
COUNT
Burst measurement count control 0x00
0x45 MEASURE_DELAY Delay between automatic
measurements
0x14
The device can be congured to take multiple measurements for each
measurement command or repeat indenitely for free running mode.
OUTER_LOOP_COUNT (0x11) controls the number of times the device will
retrigger itself. Values 0x00 or 0x01 result in the default one measurement per
command. Values 0x02 to 0xfe directly set the repetition count. Value 0xff will
enable free running mode after the host device sends an initial measurement
command.
The default delay between automatic measurements corresponds to a 10
Hz repetition rate. Set bit 5 in ACQ_CONFIG_REG (0x04) to use the delay
value in MEASURE_DELAY (0x45) instead. A delay value of 0x14 roughly
corresponds to 100Hz.
The delay is timed from the completion of each measurement. The means that
measurement duration, which varies with returned signal strength, will affect
the repetition rate. At low repetition rates (high delay) this effect is small, but
for lower delay values it is recommended to limit the maximum acquisition
count if consistent frequency is desired.
Velocity
Address Name Description Initial Value
0x09 VELOCITY Velocity measurement output --
The velocity measurement is the difference between the current measurement
and the previous one, resulting in a signed (2’s complement) 8-bit number in
cm. Positive velocity is away from the device. This can be combined with free
running mode for a constant measurement frequency. The default free running
frequency of 10 Hz therefore results in a velocity measurement in .1 m/s.
Congurable I2C Address
Address Name Description Initial Value
0x16 UNIT_ID_HIGH Serial number high byte Unique
0x17 UNIT_ID_LOW Serial number low byte Unique
0x18 I2C_ID_HIGH Write serial number high byte for
I2C address unlock
--
0x19 I2C_ID_LOW Write serial number low byte for
I2C address unlock
--
0x1a I2C_SEC_ADDR Write new I2C address after
unlock
--
0x1e I2C_CONFIG Default address response
control
0x00
The I2C address can be changed from its default value. Available addresses
are 7-bit values with a ‘0’ in the least signicant bit (even hexadecimal
numbers).
To change the I2C address, the unique serial number of the unit must be read
then written back to the device before setting the new address. The process is
as follows:
1
Read the two byte serial number from 0x96 (High byte 0x16 and low byte
0x17).
2
Write the serial number high byte to 0x18.
3
Write the serial number low byte to 0x19.
4
Write the desired new I2C address to 0x1a.
5
Write 0x08 to 0x1e to disable the default address.
This can be used to run multiple devices on a single bus, by enabling one,
changing its address, then enabling the next device and repeating the
process.
The I2C address will be restored to default after a power cycle.
Power Control
Address Name Description Initial Value
0x65 POWER_CONTROL Power state control 0x80
NOTE: The most effective way to control power usage is to utilize the enable
pin to deactivate the device when not in use.
Another option is to set bit 0 in this register which disables the receiver circuit,
saving roughly 40mA. After being re-enabled, the receiver circuit stabilizes by
the time a measurement can be performed. Setting bit 2 puts the device in
sleep mode until the next I2C transaction, saving 20mA. Since the wake-up
time is only around 2 m/s shorter than the full power-on time, and both
will reset all registers, it is recommended to use the enable pin instead.