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Item Description
4.7 kiloohm pull-up
resistor
(not required in all
applications)
I2C SDA connection
I2C SCL connection
5 Vdc power (+)
connection
Power ground (-)
connection
PWM Wiring
Item Description
Trigger pin on
microcontroller
Monitor pin on
microcontroller
Power ground (-)
connection
1 kΩ resistor
Mode control connection Yellow wire
5 Vdc power (+)
connection
PWM Arduino Wiring
Notes
In installations with long cable
extensions or with multiple devices on
the I2C bus, you must install a 1 kiloohm
to 10 kiloohm pull-up resistor on each
I2C wire to account for cable
capacitance. Garmin recommends
starting with 4.7 kiloohm resistors and
adjusting if necessary.
Blue wire
Green wire
Red wire
The sensor operates at 4.75 to 5.5 Vdc,
with a maximum of 6 Vdc.
Black wire
Notes
Connect the other side of the resistor
to the trigger pin on your
microcontroller.
Connect one side of the resistor to the
mode control connection on the device,
and to a monitoring pin on your
microcontroller.
Black wire
Red wire
The sensor operates at 4.75 to
5.5 Vdc, with a max. of 6 Vdc.
Item Description
5 Vdc power (+)
connection
Power ground (-)
connection
Mode control connection Yellow wire
Monitor pin on
microcontroller
Trigger pin on
microcontroller
1 kΩ resistor
Operational Information
Technology
This device measures distance by calculating the time delay
between the transmission of a near-infrared laser signal and its
reception after reflecting off of a target, using the known speed
of light.
Theory of Operation
When the device takes a measurement, it first performs a
receiver adjustment routine, correcting for changing ambient
light levels and allowing maximum sensitivity.
The device sends a reference signal directly from the transmitter
to the receiver. It stores the transmit signature, sets the time
delay for "zero" distance, and recalculates this delay periodically
after several measurements.
Next, the device initiates a measurement by performing a series
of acquisitions. Each acquisition is a transmission of the main
laser signal while recording the return signal at the receiver. If
there is a signal match, the result is stored in memory as a
correlation record. The next acquisition is summed with the
previous result. When an object at a certain distance reflects the
laser signal back to the device, these repeated acquisitions
cause a peak to emerge, out of the noise, at the corresponding
distance location in the correlation record.
The device integrates acquisitions until the signal peak in the
correlation record reaches a maximum value. If the returned
signal is not strong enough for this to occur, the device stops at
a predetermined maximum acquisition count.
Signal strength is calculated from the magnitude of the signal
record peak and a valid signal threshold is calculated from the
noise floor. If the peak is above this threshold, the measurement
is considered valid and the device will calculate the distance. If
the peak is not above the threshold, it will report 1 cm. When
beginning the next measurement, the device clears the signal
record and starts the sequence again.
Interface
Initialization
On power-up or reset, the device performs a self-test sequence
and initializes all registers with default values. After roughly 22
ms, distance measurements can be taken with the I2C interface
or the mode control pin.
Power Enable Pin
The power enable pin uses an internal pull-up resistor and can
be driven low to shut off power to the device.
I2C Interface
This device has a 2-wire, I2C-compatible serial interface (see
I2C-Bus Specification, Version 2.1, January 2000, available from
Philips Semiconductor). It can be connected to an I2C bus as a
Notes
Red wire
The sensor operates at 4.75 to
5.5 Vdc, with a max. of 6 Vdc.
Black wire
Connect one side of the resistor to the
mode control connection on the device,
and to a monitoring pin on your
microcontroller board.
Connect the other side of the resistor to
the trigger pin on your microcontroller
board.
3
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