Item
Sensors
Part #
White M&M
none (Sentral only)
13734
Orange M&M
BMI055+AK8963
13771
Red M&M
MPU6500+AK8963
13763
Green M&M
LSM330+AK8963
13736
Yellow M&M
LSM9SD0
13738
Blue M&M
LSM330+RM3100
13759
SENtral M&M
Motion & Measurement Modules
General Description
PNI’s SENtral M&M motion and
measurement modules provide accurate
heading and orientation data in a small, lowpower-consumption, and easy-to-integrate
package. A module incorporates the
SENtral motion coprocessor, a
magnetometer, an accelerometer, and a
gyroscope, with different SENtral M&M
versions comprising different sensor models.
Unlike other inertial measurement units
(IMUs) requiring extensive sensor fusion
algorithm development and sensor
calibration work, the Sentral M&M modules
are pre-engineered to provide high accuracy
motion tracking and heading data. And this
is obtained at a fraction of the power used
by any other solution on the market.
The SENtral M&M comes ready to integrate
into a user’s system. Designed with SMT
soldering in mind, the pins are on an
industry-standard 3 mm pitch. The on-board
EEPROM contains SENtral’s configuration
file and this automatically uploads into
SENtral RAM when powered up.
Communication is via I2C protocol.
Features
All-in-one motion & orientation tracking
module, incorporates the SENtral motion
coprocessor, 3-axis gyroscope, 3-axis
accelerometer, and 3-axis magnetometer.
Low power consumption.
11x11 mm footprint and SMT design for
ease of integration into a user’s system
Multiple test points for debugging and
evaluating performance.
Multiple versions with different sensors.
Applications
Personal Navigation & LBS
Gaming & Augmented Reality
Movement Science & Fitness
Ordering Information
With the SENtral M&M modules you can
quickly and easily incorporate industryleading motion-tracking and orientation
measurement in your mobile device. We’re
sure you’ll be impressed.
Table of Contents
1 PRODUCT OVERVIEW ............................................................................................... 3
1.1 SENTRAL FEATURES AND BENEFITS ........................................................ 3
1.2 SENTRAL M&M SYSTEM OVERVIEW .......................................................... 4
2 SENTRAL SPECIFICATIONS ..................................................................................... 6
2.1 PERFORMANCE CHARACTERISTICS ......................................................... 6
2.2 ELECTRICAL CHARACTERISTICS ............................................................... 6
3 INTERFACE ................................................................................................................. 8
3.1 I2C TIMING ...................................................................................................... 9
3.2 I2C HOST INTERFACE (HOST BUS) ........................................................... 10
3.2.1 I2C Transfer formats ......................................................................... 11
3.3 I2C SENSOR INTERFACE (SENSOR BUS) ................................................. 12
3.4 HOST INTERRUPT/GPIO LINES ................................................................. 12
4 OPERATION .............................................................................................................. 13
4.1 POWER-UP ................................................................................................... 14
4.2 INITIAL REGISTER SET-UP ......................................................................... 14
4.3 RUNNING IN NORMAL OPERATION .......................................................... 16
4.3.1 Error .................................................................................................. 18
4.3.2 Read Results .................................................................................... 18
4.4 STANDBY STATE ......................................................................................... 19
4.5 PASS-THROUGH STATE ............................................................................. 20
4.6 TROUBLESHOOTING .................................................................................. 22
4.6.1 Hardware-Related Error Conditions ................................................. 22
4.6.2 Software-Related Error Conditions ................................................... 23
5 PACKAGE INFORMATION ....................................................................................... 25
6 ASSEMBLY GUIDELINES ......................................................................................... 27
APPENDIX I – CONVERTING QUATERNIONS .................................................................... 29
APPENDIX II – PARAMETER TRANSFER ............................................................................ 31
APPENDIX III – MEASURING CURRENT CONSUMPTION ................................................. 37
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 1
List of Figures
Figure 1-1: SENtral M&M Module Reference Schematic ......................................................... 4
Figure 3-1: I2C Timing Diagram ................................................................................................ 9
Figure 3-2: I2C Slave Write Example ...................................................................................... 11
Figure 3-3: I2C Slave Read Example, with Repeated START................................................ 11
Figure 3-4: I2C Slave Write Register Address Only ................................................................ 11
Figure 3-5: I2C Slave read register from current address ....................................................... 11
Figure 4-1: SENtral Initialization Sequence ............................................................................ 13
Figure 4-2: SENtral Operational States .................................................................................. 13
Figure 4-3: SENtral Normal Operation Flow ........................................................................... 18
Figure 6-1: SENtral Orange, Red, Green, & Yellow M&M Mechanical Drawing .................... 25
Figure 6-2: SENtral White M&M Mechanical Drawing............................................................ 25
Figure 6-3: SENtral Blue M&M Mechanical Drawing.............................................................. 26
Figure 7-1: SENtral Orange, Red, Green, & Yellow M&M Solder Pad Layout ....................... 27
Figure 7-2: SENtral White M&M Solder Pad Layout .............................................................. 27
Figure 7-3: SENtral Blue M&M Solder Pad Layout ................................................................ 28
Figure A2-1: Parameter Load Process ................................................................................... 32
Figure A2-2: Parameter Retrieve Process ............................................................................. 33
Figure A3-1: SENtral Blue M&M Zero-Ohm Resistor Location .............................................. 37
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 M&M Module Pin Assignments .................................................................. 8
Table 3-2: I2C Timing Parameters .......................................................................................... 10
Table 4-1: Configuration File Upload from EEPROM Registers ............................................ 14
Table 4-2: Registers for Initial Set-up ..................................................................................... 15
Table 4-3: Normal Operation Registers .................................................................................. 17
Table 4-4: Results Registers .................................................................................................. 19
Table 4-5: Standby Registers ................................................................................................. 20
Table 4-6: Pass-Through Registers........................................................................................ 21
Table 4-7: Hardware-Related Error Indications ...................................................................... 22
Table 4-8: Software-Related Error Indications ....................................................................... 23
Table 4-9: ErrorRegister Indications ....................................................................................... 23
Table 4-10: RAMVersion Register Values .............................................................................. 24
Table A2-1: Registers Used for Parameter Transfer .............................................................. 31
Table A2-2: Parameter Numbers............................................................................................ 34
Table A2-3: DriverID & AlgorithmID Definition ....................................................................... 36
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 2
1 Product Overview
The SENtral M&M Motion and Measurement Module is a castellated printed-circuit assembly
that makes it easy to quickly integrate a complete motion-sensor-fusion system into a mobile
device. A module incorporates the SENtral Motion Coprocessor, a magnetometer, an
accelerometer, and a gyroscope, with different SENtral M&M versions integrating different
sensor models. The SENtral Motion Coprocessor manages and uses data from the three sensors to
provide reliable motion tracking and an accurate compass heading, while consuming about 1% of
the power of a comparable ARM-based sensor fusion microprocessor. SENtral outputs Euler
angles (aka heading, pitch, and roll), quaternions, and sensor data. Quaternions uniquely define
orientation and, unlike Euler angles, do not experience a singularity (i.e. gimbal lock) when
pointing straight up. They easily can be converted to Euler angles, the rotation vector, and the
rotation matrix (aka DCM), as discussed in Appendix I.
1.1 SENtral Features and Benefits
At the heart of the SENtral M&M module is PNI’s revolutionary SENtral Motion
Coprocessor. Listed below are some of the features and benefits of this device.
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 auto-calibration. Unlike other motion-tracking
products, SENtral calibrates for both hard-iron and soft-iron magnetic distortion.
Specifically, soft-iron distortion is quite difficult to correct, and can contribute up to
90° of error. It can be caused by materials widely used in mobile and consumer
electronic devices, such as EMI shielding tape and other shielding. Additionally,
since a host system’s magnetic signature can change over time and temperature,
SENtral’s continuous auto-calibration ensures accuracy over time.
Magnetic anomaly compensation. With SENtral, heading and motion tracking is
unaffected by short-term magnetic anomalies, such as rebar in buildings, desks,
speakers etc., that can easily throw off the accuracy. SENtral establishes if a transient
magnetic anomaly is present and compensates for this.
Sensor flexibility. SENtral works with most common consumer electronics motion
sensors, so designers can choose the sensors most appropriate for their systems.
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 3
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.
I2C interface. Uses industry-standard I2C protocol in a low-power implementation 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 natively outputs Euler angles (heading, pitch, and roll),
quaternions, rotational velocity, linear acceleration, and magnetic field.
Pass-Through allows for direct communication with devices on the I2C sensor bus.
1.2 SENtral M&M System Overview
Figure 1-1 provides a reference schematic for SENtral M&M modules. While this diagram
applies for most versions of the SENtral M&M, the White and Blue M&M modules differ
from what is shown. Specific schematics for each module are available from PNI on request.
How to interface with the SENtral M&M is covered in more detail in Section 3.
Figure 1-1: SENtral M&M Module Reference Schematic
A few points on diagram:
The layout shows a discrete magnetometer, accelerometer, and gyroscope. SENtral
M&M modules generally incorporate a combo sensor that combines the gyroscope
and accelerometer into a single device or all three sensors into a single device.
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 4
SENtral acts as a slave on a host system I2C bus. This does not need to be a dedicated
bus, although it is shown this way in the schematic.
The SCLM and SDAM lines can be used to monitor SENtral’s I2C sensor bus, but
this is not necessary. These lines are optional and may be left unconnected.
If the host will poll SENtral, rather than running in an interrupt-driven manner, it is
not necessary to connect GPIO[6], the host interrupt line, to the host system.
GPIO[4] is intended for future use and currently serves no purpose. This can be left
unconnected.
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 5
Parameter
Minimum
Typical
Maximum
Units
Heading Accuracy
2
° rms
Output Data Rate
200
400
Hz
Parameter
Symbol
Minimum
Maximum
Units
Supply Voltage
VDD
-0.3
+3.6
VDC
Input Pin Voltage
VIN
GND – 0.3
VDD + 0.3
VDC
Storage Temperature
-50°
+150°
C
2 SENtral Specifications1
2.1 Performance Characteristics
Table 2-1: Performance Characteristics
2.2 Electrical Characteristics
Table 2-2: Absolute Maximum Ratings
CAUTION:
Stresses beyond those listed above may cause permanent damage to the device. These
are stress ratings only. Operation of the device at these or other conditions beyond those
indicated in the operational sections of the specifications is not implied.
Footnote
1. Specifications subject to change.
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 6
Parameter
Symbol
Min
Typ
Max
Units
Digital Supply Voltage – Sensors &
EEPROM
DVDD
1.71
AVDD
VDC
Supply Voltage – SENtral
DVDD2
1.6 3.3
VDC
Analog Supply Voltage – Sensors
AVDD
2.4 3.6
VDC
Power-On Reset Threshold
V
POR
1.0 VDC
High Level Input Voltage
VIH
0.7*VDD
VDD
VDC
Low Level Input Voltage
VIL 0
0.3*VDD
VDC
High Level Output Current, VOH = VDD – 0.3V
IOH
-1
mA
Low Level Output Current, VOL = 0.3V
IOL 1 mA
I2C Interface
Data Rate1
Host Bus
3400
kbits/sec
Sensor Bus
1000
kbits/sec
Pass-Through
400
kbits/sec
Operating Temperature
TOP
-40
+25
+85
C
Table 2-3: Operating Conditions
Footnote:
1. SENtral’s I2C Host Interface supports Standard, Fast, Fast Plus, and High Speed Modes.
High Speed Mode (3400 kHz) is supported with a reduced range of VDD and bus
capacitance. SENtral’s I
Modes. Pass-Through state, which connects the sensor bus and host bus, supports
Standard and Fast Modes.
2
C sensor bus interface supports Standard, Fast, and Fast Plus
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 7
Pin Name
Description
M&M Orange,
Red, Green, &
Yellow Pin#
M&M
White
Pin #
M&M
Blue
Pin #
DVDD
Digital Supply Voltage – Sensors &
EEPROM
1
NA
2
DVDD2
Supply Voltage – SENtral
2
D1
2
AVDD
Analog Supply Voltage – Sensors
7
NA
7
GND
Ground 8 D2
8
SCLS
I2C host bus SCL clock line
3
B1
3
SDAS
I2C host bus SDA data line
5
A1
5
SDAM
I2C sensor bus SDA data line
9
A4
9
SCLM
I2C sensor bus SCL clock line
10
B4
10
GPIO[0]
SENtral Accelerometer Interrupt
--
D4
--
GPIO[1]
SENtral Magnetometer Interrupt
--
C4
--
GPIO[2]
SENtral Gyroscope Interrupt
--
A3
--
GPIO[3]
Reserved
--
B3
--
GPIO[4]
Reserved
6
A2
6
GPIO[5]
Reserved
--
B2
--
GPIO[6]
Host Event Interrupt
4
C1
4
SA0
Slave Address Pin 0
--
C3
--
VCAP
Regulator Capacitor
--
D3
--
Reserved
Reserved (not connected)
--
C2
1, 12, 13
3 Interface
The SENtral M&M pin-out is given in Table 3-1. Pin-outs also are given alongside the device
mechanical drawings in Section 5. See Table 2-3 for the operating ranges of DVDD, DVDD2,
and AVDD. A discussion of the communication interface follows the table.
Table 3-1: SENtral M&M Module Pin Assignments
Communication with the host processor is via SENtral’s I2C host interface, where the SENtral
M&M acts as a slave device and the host’s processor acts as the master. The host interrupt line
informs the host system when SENtral has updated measurement data. The SENtral Motion
Coprocessor on the SENtral M&M module communicates with the module’s sensors over the
sensor bus, where SENtral is the I2C master and the sensors are slave devices.
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 8
SENtral’s I2C interfaces comply with NXP’s UM10204 specification and user manual, rev 04.
Standard, Fast, Fast Plus, and High Speed modes of the I2C protocol are supported by SENtral’s
I2C host interface. Below is a link to this document.
http://www.nxp.com/documents/user_manual/UM10204.pdf
3.1 I2C Timing
SENtral’s I2C timing requirements are set forth below, in Figure 3-1 and Table 3-2. For the
timing requirements shown in Figure 3-1, transitions are 30% and 70% of VDD.
Figure 3-1: I2C Timing Diagram
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 9
Standard
Fast
Fast Plus
Units
Symbol
Parameter
Min
Max
Min
Max
Min
Max
f
SCL
SCL Clock
0
100 0 400
0
1000
kHz
tr
SDA & SCL Rise
Time
-
1000
20
300 120
ns
tf
SDA & SCL Fall Time
-
300
20*(VDD/
5.5V)
300
20*(VDD/
5.5V)
120
ns
t
LOW
LOW period of SCL
Clock
4.7 - 1.3 - 0.5
-
s
t
HIGH
HIGH period of SCL
Clock
4.0 - 0.6 - 0.26
-
s
t
HD;STA
Hold time (repeated)
START
4.0 - 0.6 - 0.26
-
s
t
HD;DAT
Data hold time
0 - 0 - 0
-
s
t
SU:DAT
Data set-up time
250 - 100 - 50 - ns
t
SU;STA
Set-Up time for
repeated Start
4.7 - 0.6 - 0.26
-
s
t
SU;STO
Stop set-up time
4.0 - 0.6 - 0.26
-
s
t
BUF
Bus free time between
STOP & START
4.7 - 1.3 - 0.5
-
s
Table 3-2: I2C Timing Parameters
3.2 I2C Host Interface (Host Bus)
The host will control the SENtral M&M on the host bus via SENtral’s I2C host interface.
The host interface consists of 2 wires: the serial clock, SCLS, and the serial data line, SDAS.
Both lines are bi-directional. SENtral is connected to the host bus via the SDAS and SCLS
pins, which incorporate open drain drivers within the device. Note the SENtral M&M
module incorporates 4.7 kΩ pull-up resistors on the host bus clock and data lines, so if the
host system also incorporates pull-up resistors on these line the resistors will act in parallel.
The SENtral M&M’s 7-bit I2C slave address is 0x28 (0b0101000). The shifted address is
0x50.
Data transfer is always initiated by the host. Data is transferred between the host and
SENtral serially through the data line, SDAS, in an 8-bit transfer format. The transfer is
synchronized by the serial clock line, SCLS. Supported transfer formats are single-byte read,
multiple-byte read, single-byte write, and multiple-byte write. The data line can be driven
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 10
START
SLAVE ADDRESS
RW
ACK
REGISTER ADDRESS (N)
ACK
DATA TO REGISTER (N)
ACK
DATA TO REGISTER (N+1)
ACK
STOP
S
A6
A5
A4
A3
A2
A1
A0 0 0
R7
R6
R5
R4
R3
R2
R1
R0 0 D7
D5
D4
D3
D2
D1
D0 0 D7
D5
D4
D3
D2
D1
D0 0 P
From Host to SENtral
------------ Data Transferred (n bytes + acknowledge) ------------
From SENtral to Host
START
SLAVE ADDRESS
RW
ACK
REGISTER ADDRESS (N)
ACK
START
SLAVE ADDRESS
RW
ACK
DATA FROM REGISTER (N)
NACK
STOP
S
A5
A4
A3
A2
A1
A0 0 0
R7
R5
R4
R3
R2
R1
R0 0 SR
A6
A5
A4
A3
A2
A1
A0 1 0
D7
D5
D4
D3
D2
D1
D0 1 P
Data Transferred
(n bytes + acknowledge)
START
SLAVE ADDRESS
RW
ACK
REGISTER ADDRESS (N)
ACK
STOP
S
A5
A4
A3
A2
A1
A0 0 0
R7
R5
R4
R3
R2
R1
R0 0 P
START
SLAVE ADDRESS
RW
ACK
DATA FROM REG. (N)
ACK
DATA FROM REG. (N+1)
NACK
STOP
S
A5
A4
A3
A2
A1
A0 1 0
D7
D5
D4
D3
D2
D1
D0 0 D7
D5
D4
D3
D2
D1
D0 1 P
From Host to SENtral
-------------- Data Transferred (n bytes + acknowledge) --------------
From SENtral to Host
either by the host or SENtral. Normally the serial clock line will be driven by the host,
although exceptions can exist when clock-stretching is implemented in Pass-Through State.
3.2.1 I2C Transfer formats
Figure 3-2 illustrates writing data to registers in single-byte or multiple-byte mode.
Figure 3-2: I2C Slave Write Example
The I2C host interface supports both a read sequence using repeated START conditions,
shown in Figure 3-3, and a sequence in which the register address is sent in a separate
sequence than the data, shown in Figure 3-4 and Figure 3-5.
Figure 3-3: I2C Slave Read Example, with Repeated START
Figure 3-4: I2C Slave Write Register Address Only
Figure 3-5: I2C Slave read register from current address
PNI Sensor Corporation Doc #1020129 revE
SENtral M&M Technical Datasheet Page 11
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