SENtral
Motion Coprocessor
General Description
The SENtral
Motion Coprocessor is a
custom integrated circuit that makes it easy
to quickly incorporate, optimize and operate
multiple motion sensors on mobile
consumer electronics devices.
SENtral
employs and manages a user-specified
3-axis magnetometer, 3–axis accelerometer,
and 3–axis gyroscope to provide reliable
motion tracking, and accurate heading and
orientation data. SENtral gathers data from
the individual sensors, then integrates and
fuses this data using PNI‟s proprietary
Kalman filtering and heuristic algorithms.
By offloading the sensor fusion and
interface from a dedicated sensor hub MCU
or the host CPU to SENtral, overall power
requirements are dramatically lowered and
processing power is opened up for other
uses.
These advantages make SENtral the ideal
choice for mobile and consumer electronics
devices
desiring
ultra-lower
power
consumption and best-in-class sensor fusion.
Features
Heading Accuracy of 2° rms.
Ultra Low Power Consumption
Continuous Soft and Hard-Iron
Magnetic Auto-Calibration
Magnetic Anomaly
Compensation
I
2
C Interface – 100 to 3400 kHz
Small Form-Factor
Sensor Flexibility
Applications
Cell Phones
Tablets
Ultrabooks
TV Remote Controls
Video Game Controllers
Ordering Information
Item
SENtral
SENtral
Part #
13658P
13658
Quantity Package
<4000
4000
Cut-Tape
Tape & Reel
Table of Contents
1
PRODUCT OVERVIEW ............................................................................................... 3
1.1
SENTRAL FEATURES AND BENEFITS ........................................................ 3
1.2
SENTRAL FUNCTIONAL DESCRIPTION ...................................................... 4
1
2
SENTRAL SPECIFICATIONS .................................................................................... 6
2.1
PERFORMANCE CHARACTERISTICS ......................................................... 6
2.2
ELECTRICAL CHARACTERISTICS ............................................................... 6
3
LAYOUT ....................................................................................................................... 8
3.1
SYSTEM LAYOUT .......................................................................................... 8
3.2
PIN ASSIGNMENTS ....................................................................................... 9
3.3
SENSOR LAYOUT ........................................................................................ 10
3.4
DEDICATED EEPROM (OPTIONAL) ........................................................... 11
2
4
I C INTERFACE ......................................................................................................... 12
2
4.1
I C TIMING .................................................................................................... 12
2
4.2
I C HOST INTERFACE (HOST BUS) ........................................................... 13
2
4.2.1 I C Slave Transfer formats ............................................................... 14
2
4.3
I C SENSOR INTERFACE (SENSOR BUS) ................................................. 15
2
4.4
I C PULL-UP RESISTANCE ......................................................................... 15
5
OPERATION .............................................................................................................. 16
5.1
POWER-UP AND CONFIGURATION FILE UPLOAD .................................. 17
5.1.1 Configuration File Upload from EEPROM ........................................ 17
5.1.2 Configuration File Upload from Host ................................................ 19
5.2
INITIAL REGISTER SET-UP ......................................................................... 20
5.3
RUNNING IN NORMAL OPERATION .......................................................... 22
5.3.1 Error .................................................................................................. 24
5.3.2 CPUReset ......................................................................................... 24
5.3.3 Read Results .................................................................................... 24
5.4
STANDBY STATE ......................................................................................... 25
5.5
PASS-THROUGH STATE ............................................................................. 26
5.6
TROUBLESHOOTING .................................................................................. 28
5.6.1 Hardware-Related Error Conditions ................................................. 28
5.6.2 Software-Related Error Conditions ................................................... 28
6
SENTRAL CONFIGURATION TOOL ........................................................................ 31
6.1
CONFIGURATION TOOL GENERAL SETTINGS ........................................ 32
6.1.1 SDK Revision ................................................................................... 32
6.1.2 Host Interrupt Pin .............................................................................. 32
6.1.3 EEPROM Max. Upload Speed ......................................................... 32
6.2
CONFIGURATION TOOL SENSOR CONFIGURATION .............................. 32
6.2.1 Sensor .............................................................................................. 32
6.2.2 Interrupt Pin ...................................................................................... 32
6.2.3 Slave Address .................................................................................. 32
6.2.4 Orientation Matrix ............................................................................. 33
6.2.5 Cal Offsets ........................................................................................ 34
7
PACKAGE INFORMATION ....................................................................................... 35
8
ASSEMBLY GUIDELINES ......................................................................................... 37
APPENDIX I – CONFIGURATION FILE IMAGE FORMAT.................................................... 40
APPENDIX II – CONVERTING QUATERNIONS ................................................................... 42
APPENDIX III – PARAMETER TRANSFER ........................................................................... 44
APPENDIX IV – SAMPLE SCHEMATIC SET ........................................................................ 50
PNI Sensor Corporation
SENtral Technical Data Sheet
Doc #1018049 R06
Page 1
List of Figures
Figure 1-1: SENtral Block Diagram .......................................................................................... 4
Figure 3-1: SENtral System Reference Schematic .................................................................. 8
2
Figure 4-1: I C Timing Diagram .............................................................................................. 12
2
Figure 4-2: I C Slave Write Example ...................................................................................... 14
2
Figure 4-3: I C Slave Read Example, with Repeated START................................................ 14
2
Figure 4-4: I C Slave Write Register Address Only ................................................................ 14
2
Figure 4-5: I C Slave read register from current address ....................................................... 14
Figure 5-1: SENtral Initialization Sequence ............................................................................ 16
Figure 5-2: SENtral Operational States .................................................................................. 17
Figure 5-3: SENtral Normal Operation Flow ........................................................................... 23
Figure 6-1: SENtral Configuration Tool .................................................................................. 31
Figure 7-1: Mechanical Drawing ............................................................................................. 35
Figure 7-2: Tape Dimensions ................................................................................................. 36
Figure 8-1: Typical Solder Mask and Land Pad Parameters ................................................. 38
Figure 8-2: Typical Solder Reflow Profile ............................................................................... 39
Figure A3-1: Parameter Load Process ................................................................................... 46
Figure A3-2: Parameter Retrieve Process ............................................................................. 47
List of Tables
Table 2-1: Performance Characteristics ................................................................................... 6
Table 2-2: Absolute Maximum Ratings .................................................................................... 6
Table 2-3: Operating Conditions............................................................................................... 7
Table 3-1: SENtral Pin Assignments ........................................................................................ 9
Table 3-2: Recommended Power Line Distance from Magnetometer ................................... 11
2
Table 4-1: I C Timing Parameters .......................................................................................... 13
2
Table 4-2: I C Pull-Up Resistance Table ................................................................................ 15
Table 5-1: Configuration File Upload from EEPROM Registers ............................................ 18
Table 5-2: Configuration File Host Upload Registers ............................................................. 19
Table 5-3: Sample Host Upload Data Order .......................................................................... 20
Table 5-4: Registers for Initial Set-Up .................................................................................... 20
Table 5-5: Normal Operation Registers .................................................................................. 23
Table 5-6: Results Registers .................................................................................................. 25
Table 5-7: Standby Registers ................................................................................................. 25
Table 5-8: Pass-Through Registers........................................................................................ 27
Table 5-9: Hardware-Related Error Indications ...................................................................... 28
Table 5-10: Software-Related Error Indications ..................................................................... 28
Table 5-11: SensorStatus Register Values ............................................................................ 29
Table 5-12: ErrorRegister Values ........................................................................................... 29
Table 5-13: RAMVersion Register Values .............................................................................. 30
Table 8-1: Typical Solder Processing Parameters ................................................................. 39
Table A1-1: Configuration File Image Format ........................................................................ 40
Table A1-2: Configuration File Data Structure ....................................................................... 41
Table A3-1: Registers Used for Parameter Transfer .............................................................. 44
Table A3-2: Parameter Numbers............................................................................................ 48
Table A3-3: DriverID & AlgorithmID Definition ....................................................................... 49
PNI Sensor Corporation
SENtral Technical Data Sheet
Doc #1018049 R06
Page 2
1
Product Overview
The SENtral
Motion Coprocessor is an integrated circuit that makes it easy to quickly integrate,
optimize and operate multiple sensors on mobile consumer electronics devices.
SENtral
manages
and uses data from a user-specified 3-axis gyroscope, 3-axis accelerometer, and 3-axis
magnetometer to provide reliable motion tracking and an accurate compass heading, while
consuming about 1% of the power of a comparable sensor fusion microprocessor.
Note:
This revision of the SENtral Technical Datasheet applies to Configuration Files of revision 1.1 or
higher. The Configuration File is discussed in Sections 1.2, 5.1, 5.6.2, and 6, and
Appendix I.
It is
generated by the SENtral Configuration Tool and is uploaded into SENtral RAM after power up.
1.1 SENtral Features and Benefits
Features and benefits of the SENtral Motion Coprocessor include:
Low power consumption.
Offloads sensor processing from the less efficient host
CPU, consuming <1% of the power of a Cortex M0 running a comparable sensor
fusion algorithm. Provides the ability to tailor the tradeoff between power
consumption and motion-tracking performance.
Industry-leading heading accuracy.
Unparalleled heading accuracy for consumer
electronics applications.
Continuous hard and soft-iron magnetic auto-calibration.
Provides continual
background calibration of the sensors. Leverages PNI‟s more than 20 years of
experience and expertise in magnetic measurement.
Magnetic anomaly compensation.
Heading and motion tracking is unaffected by
magnetic anomalies such as rebar in buildings, desks, speakers etc., that can easily
throw off the accuracy. SENtral recognizes and compensates for these anomalies.
Sensor flexibility.
Works with common consumer electronic MEMS motion sensors,
so system designers can choose the sensors most appropriate for their systems.
Small form-factor.
1.6x1.6x0.5 mm chip-scale package on 0.4 mm pitch. Uses little
PCB real estate, allowing for painless integration.
I
2
C interface.
Uses the industry-standard I
2
C protocol to interface to the sensors and
the host, so system integration is straightforward. Standard, Fast, Fast Plus, and High
Speed are supported on the host bus.
Outputs.
SENtral outputs quaternions, Euler angles (heading, pitch, & roll), and
sensor data (rotational velocity, linear acceleration, & magnetic field).
PNI Sensor Corporation
SENtral Technical Data Sheet
Doc #1018049 R06
Page 3
1.2 SENtral Functional Description
Figure 1-1 provides a diagram of SENtral‟s primary functional blocks, and a brief description
of these functional blocks follows.
Figure 1-1: SENtral Block Diagram
Quaternion
generates the orientation output, where the actual orientation outputs can
be quaternions or Euler angles (heading, pitch, & roll). The outputs are updated at a
rate limited to the gyro output data rate (ODR), to a maximum of 400 Hz.
Kalman Update
fuses data from the 3-axis gyroscope, 3-axis accelerometer, and 3-
axis magnetometer, plus data from the magnetic anomaly determination and
continuous auto-calibration blocks to generate intelligent orientation updates. The
Kalman update involves a sophisticated multi-state Kalman algorithm.
Continuous Hard and Soft-Iron Auto-Calibration.
SENtral is the only product in
the market that auto-calibrates for both hard-iron and soft-iron magnetic distortions.
While others may calibrate for hard-iron distortion, soft-iron distortion is more
difficult to correct for, and it can be caused by EMI shielding tape and other shielding
materials widely used in mobile and consumer electronic devices. It is important to
correct for soft-iron distortions since these can contribute up to 90° of error.
Additionally, since a host system‟s magnetic signature can change over time and
temperature, SENtral‟s continuous auto-calibration ensures accuracy all the time.
Doc #1018049 R06
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PNI Sensor Corporation
SENtral Technical Data Sheet
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