Data Sheet

Digital interfaces LSM9DS1
28/72 DocID025715 Rev 2
5 Digital interfaces
The registers embedded inside the LSM9DS1 may be accessed through both the I
2
C and
SPI serial interfaces. The latter may be SW configured to operate either in 3-wire or 4-wire
interface mode.
The serial interfaces are mapped onto the same pins. To select/exploit the I
2
C interface, the
CS line must be tied high (i.e connected to Vdd_IO).
5.1 I
2
C serial interface
The LSM9DS1 I
2
C is a bus slave. The I
2
C is employed to write the data to the registers,
whose content can also be read back.
The relevant I
2
C terminology is provided in the table below.
There are two signals associated with the I
2
C bus: the serial clock line (SCL) and the Serial
DAta line (SDA). The latter is a bidirectional line used for sending and receiving the data
to/from the interface. Both the lines must be connected to Vdd_IO through an external pull-
up resistor. When the bus is free, both the lines are high.
The I
2
C interface is implemented with fast mode (400 kHz) I
2
C standards as well as with the
standard mode.
In order to disable the I
2
C block for accelerometer and gyroscope the I2C_DISABLE bit
must be written to ‘1’ in CTRL_REG9 (23h), while for magnetometer the I2C_DISABLE bit
must be written to ‘1’ in CTRL_REG3_M (22h).
Table 13. Serial interface pin description
Pin name Pin description
CS_A/G, CS_M
SPI enable
I
2
C/SPI mode selection (1: SPI idle mode / I
2
C communication enabled; 0: SPI
communication mode / I
2
C disabled)
SCL/SPC
I
2
C Serial Clock (SCL)
SPI Serial Port Clock (SPC)
SDA/SDI/SDO
I
2
C Serial Data (SDA)
SPI Serial Data Input (SDI)
3-wire Interface Serial Data Output (SDO)
SDO_A/G, SDO_M
SPI Serial Data Output (SDO)
I
2
C less significant bit of the device address
Table 14. I
2
C terminology
Term Description
Transmitter The device which sends data to the bus
Receiver The device which receives data from the bus
Master
The device which initiates a transfer, generates clock signals and terminates a
transfer
Slave The device addressed by the master