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Electrical Data Connection and Addressing
Enabling the SPI/I2C interface is controlled by Pin 2 (SPI/I2C Enable). Applying power to Pin 2
(from pin 6) disables USB connectivity and enables the SPI/I2C interface. Choosing SPI or I2C for a
LB5900 sensor is done using Pin 1 of the interface cable. Applying power (from Pin 6), selects I2C
and disables SPI, grounding the pin will enable SPI and disable I2C.
When using I2C, external pull-up resistors are required, refer to Figure 2. LadyBug's nominal
recommended value is 2.2K ohms. The pull-up resistors should be connected to the
microcontroller's logic power supply (3.3-5.0 volts) near the microcontroller. High speed
applications may benefit from a capacitor to ground on I2C data and clock lines. Recommended
starting value is 27pf. The resistor and capacitor values can be optimized to reduce overshoot.
Up to four sensors may be addressed on a single I2C connection. Each sensor's address is set by
hardware. When I2C is selected the device address is as shown in Table 1.
Address
1001100
1001101
1001110
1001111
DOC: SPII2CHDWBrief - V2.71 07/25/2017
USING I2C
Connector Pin 5
SPI
MOSI or I2C Adr1
0
0
1
1
Figure 3 - I2C Device Address
Figure 4 - Typical I2C Connection
Connector Pin 3
SPI SS or I2C Adr0
0
1
0
1
PAGE 8
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