Data Sheet

ICM-20948
Document Number: DS-000189 Page 24 of 89
Revision: 1.3
ICM-20948
SDO
SCLK
SDI
Digital
Motion
Processor
(DMP)
Sensor
Master I
2
C
Serial
Interface
Interrupt
Status
Register
FIFO
Config
Register
Sensor
Register
Factory
Calibration
nCS
Slave I
2
C
or SPI
Serial
Interface
System
Processor
Interface
Bypass
Mux
SDI
SCLK
SDO
nCS
Processor SPI Bus: for reading all
data from MPU and for configuring
MPU and external sensors
AUX_CL
AUX_DA
External
Sensor
SCL
SDA
Optional
I
2
C Master performs
read and write
transactions on
Sensor I
2
C bus.
Sensor I
2
C Bus: for
configuring and
reading data from
external sensors
VDD
Bias & LDOs
GND REGOUT
INT1
Figure 7. ICM-20948 Solution Using SPI Interface
4.12 AUXILIARY I
2
C SERIAL INTERFACE
The ICM-20948 has an auxiliary I
2
C bus for communicating to external sensors. This bus has two operating modes:
• I
2
C Master Mode: The ICM-20948 acts as a master to any external sensors connected to the auxiliary I
2
C bus
• Pass-Through Mode: The ICM-20948 directly connects the primary and auxiliary I
2
C buses together, allowing
the system processor to directly communicate with any external sensors.
Auxiliary I
2
C Bus Modes of Operation:
• I
2
C Master Mode: Allows the ICM-20948 to directly access the data registers of external sensors. In this
mode, the ICM-20948 directly obtains data from auxiliary sensors without intervention from the system
applications processor. The I
2
C Master can be configured to read up to 24 bytes from up to 4 auxiliary
sensors. A fifth sensor can be configured to work single byte read/write mode.
• Pass-Through Mode: Allows an external system processor to act as master and directly communicate to the
external sensors connected to the auxiliary I
2
C bus pins (AUX_DA and AUX_CL). In this mode, the auxiliary I
2
C
bus control logic of the ICM-20948 is disabled, and the auxiliary I
2
C pins AUX_CL and AUX_DA (pins 7 and 21)
are connected to the main I
2
C bus (Pins 23 and 24) through analog switches internally. Pass-Through mode is
useful for configuring the external sensors.
4.13 SELF-TEST
Self-test allows for the testing of the mechanical and electrical portions of the sensors. The self-test for each
measurement axis can be activated by means of the gyroscope and accelerometer self-test registers.
When the self-test is activated, the electronics cause the sensors to be actuated and produce an output signal. The
output signal is used to observe the self-test response.
The self-test response is defined as follows:
S
ELF-TEST RESPONSE = SENSOR OUTPUT WITH SELF-TEST ENABLED – SENSOR OUTPUT WITHOUT SELF-TEST ENABLED