Kauai Labs VMX-pi User manual

Hardware Reference Manual
Version 1.10
Figure 1 VMX-pi configured with Raspberry Pi 3

VMX-pi Hardware Reference Manual (version 1.10) 2
Contents
Feature Summary......................................................................................................................................3
Technical Specifications ............................................................................................................................ 5
I/O Summary.............................................................................................................................................8
I/O Resource Summary ...........................................................................................................................10
Channel/Resource Routing .................................................................................................................10
I/O Channel Types/Numbers .................................................................................................................. 11
High Current DIO Input/Output Selection Jumper .............................................................................12
Power Management Scheme..................................................................................................................13
VMX-pi Power Management...............................................................................................................14
External Device Power/Signal Voltage Configuration.............................................................................16
Signal Voltage Select Jumpers.............................................................................................................16
Power Voltage Select Jumpers............................................................................................................16
VMX-pi I/O Signal/Logic Levels ...............................................................................................................16
Board-edge Connectors ..........................................................................................................................18
FlexDIO Connectors (VMX Channels 0-7)............................................................................................18
FlexDIO Header (VMX Channels 8-11) ................................................................................................19
High-Current DIO Header (VMX Channels 12-21)...............................................................................19
Analog Input Header (VMX Channels 22-25) ......................................................................................20
CommDIO Connectors (VMX Channels 26-33) ...................................................................................21
CAN Connector....................................................................................................................................21
CAN Termination Jumper....................................................................................................................21
Micro-USB Connector .........................................................................................................................22
Input Power Connector.......................................................................................................................22
Battery & Real-time Clock.......................................................................................................................22
40-pin Raspberry Pi Connector ...............................................................................................................23
Optional 5V Fan Connector..................................................................................................................... 23
LEDs.........................................................................................................................................................23
Buttons....................................................................................................................................................24
Physical Dimensions................................................................................................................................25

VMX-pi Hardware Reference Manual (version 1.10) 3
Feature Summary
VMX-pi is designed to control a reliable, intelligent robot that is tele-operated, semi-autonomous or
fully-autonomous when combined with an inexpensive Raspberry Pi-based processor. VMX-pi is also
usable as a Vision/Motion co-processor when paired with another robot controller.
The current recommended Raspberry Pi model 3(shown in picture on the cover
page of this document); the Raspberry Pi Zero W may also be used although it provides only a subset of
the Raspberry Pi 3 capabilities.
1GB DDR
RAM
4-core 1.2Ghz
64-bit ARM
Cortex-A53
Bluetooth
4.1 HDMI
Ethernet
Networking
2.4Ghz
802.11 Wifi
Broadcom
VideoCore IV
GPU (400Mhz)
Raspberry Pi 3
4 USB 2.0
Ports
SD Card
VMX-pi + Raspberry Pi 3 Key Components
CSI Camera
Interface
USB
Data/
Config
Port
100Mhz 32-
bit ARM
Cortex-M4 w/
FPU
9-axis Inertial
Sensor/
Motion
Processor
Voltage Regulator
w/5 and 3.3V
Outputs
VMX-pi
Barometer
(optional)
Battery-backed
Realtime Clock
30 Digital I/Os
4 Analog I/Os;
SPI, I2C, TTL
UART
CAN
Interface External Device
Current-limiting
Figure 2 VMX-pi & Raspberry Pi Key Components

VMX-pi Hardware Reference Manual (version 1.10) 4
Component
Function
Key Attributes
Voltage Regulator
w/wide input
voltage range
Converts unregulated 6-16VDC to 5V & 3.3V,
up to a maximum of 3A; includes real-time
under-voltage management
Can provide 2.1A to Raspberry
Pi and .5A to external devices at
input voltages as low as 6VDC
External Device
Current Limiting
Switch & Short-
circuit protection
External 5/3.3V supplies are current limited at
.5A, to ensure full power is always provided
to the Raspberry Pi processor and VMX-pi
microcontroller
Processors continue running
even when external devices
draw excessive power or when
short-circuits occur
5/3.3V Voltage
Translation
Flexibly supports signaling with 5V and 3.3V
external devices
Eliminates need for external
voltage translation devices
Battery-backed
Real-time Clock
(RTC)
When VMX-pi is used in environments
without Network Time Server access,
provides real-time clock for distributed sensor
data alignment and accurate log timestamps
Includes CR2032 battery
w/expected life of 5 years
before replacement
100Mhz 32-bit
ARM-M4 w/FPU
Microcontroller
(STM32F411)
Implements real-time IO and timer functions,
IMU sensor data fusion, CAN bus message
buffering and Power/Brownout Management
Field-upgradable firmware can
be updated w/new features and
bugfixes
30 Digital I/Os
with overvoltage
protection
Flexible digital IO support including PWM
Generation on outputs, PWM Capture, Quad
Encoder decode, Interrupt Generation on
inputs
•PWM Generation on all
outputs
•PWM Capture o
inputs
•Interrupt Generation on all
inputs
•Quadrature Encoder decode

4 Analog I/Os with
overvoltage
protection
12-bit ADC providing 46.5k samples/sec on
each channel
Over-sampling and Averaging
Engine; Analog Triggering
supporting Interrupt generation
on Analog Inputs
CAN Interface
CAN 2.0b transceiver and controller
supporting message transmission/reception
and filtering
1 mbps bus data rate supported
9-axis Inertial
Sensor/Motion
Processor
Generates Yaw/Pitch/Roll measures as well as
Quaternions and raw gyro/accelerometer/
magnetometer data; also includes automatic
calibration software w/flash-based storage of
calibration data
Invensense MPU-9250 and
navX-Technology Kauai Labs
firmware
I2C Support
2 Comm DIO Channels can be configured for
I2C communication w/built-in pullup resistors
400Khz I2C communication
supported
TTL UART Support
2 Comm DIO Channels can be configured for
TTL UART communication
115.2 kbps UART
communication supported

VMX-pi Hardware Reference Manual (version 1.10) 5
Table 1 VMX-pi Component Functions & Attributes
Technical Specifications
VMX-pi Technical Specifications are summarized in the table below. Note that certain specifications
may be improved over time due to firmware updates. For the most up-to-date technical specifications,
-pi.kauailabs.com.
ELECTRICAL SPECIFICATIONS
Input Voltage:
6-16V DC
Output Voltages:
5V, 3.3V for External Devices
5V for Raspberry Pi
Protection Features:
Input Power Under-voltage Management
Output Power Current Limiting/Short-circuit Protection
Input Signal Over-voltage Protection
Communications Interface:
USB, I2C, SPI, CAN, UART
Power Connector:
2-Pin JST VH Connector
USB Connector:
USB Micro-B (can provide standalone power to VMX-
pi microcontroller)
IMU PERFORMANCE SPECIFICATIONS
Note: Certain IMU performance specifications are only valid after a start-up gyroscope/accelerometer calibration
period, during which time the VMX-pi circuit board must be held still.
SPI Support
4 Comm DIO Channels can be configured for
SPI communication
8Mhz SPI communication
supported
Locking
Connectors
Locking Power, FlexDIO and CAN connectors
Helps ensure electrical circuits
are not affected by vibration
Micro-USB
external interface
Additional dedicated USB interface on VMX-pi
Enables remote access to IMU
data, and VMX-pi
configuration/firmware update

VMX-pi Hardware Reference Manual (version 1.10) 6
Startup Calibration Period:
15 seconds
Gyro Sensitivity:
+/- 2000 degrees/sec
Accel Sensitivity:
+/- 2 g
Magnetometer Sensitivity:
1.3 Gauss
Yaw angle accuracy:
~1 degree of drift/minute
Yaw angle accuracy (when still):
~.25 degree of drift/minute
Orientation Data Update Rate:
4-200 Hz
Magnetometer Raw Update Rate:
4 Hz
Magnetometer Angular Accuracy:
+/- 2 degrees
Pitch/Roll Angular Accuracy:
+/- 1.5 degrees
ANALOG INPUT SPECIFICATIONS
Number of Channels:
4
Resolution:
12 bits
Per-channel Sampling Rate:
46.5K samples/sec
DIGITAL IO SPECIFICATIONS
Total Number of Channels:
30
Number of Input-capable & Interrupt-capable Channels:
26
Number of Output-capable & PWM-capable Channels:
28

VMX-pi Hardware Reference Manual (version 1.10) 7
Number of Quadrature Encoder Channel Pairs
(Hardware-decode):
5
Number of PWM Capture Inputs
6
DIGITAL COMMUNICATION SPECIFICATIONS
CAN Protocol (2.0b)
1mbps
SPI Protocol
8 Mhz
I2C Protocol
400 kHz
USB Protocol
12 mbps
UART Protocol
115,200 bps

VMX-pi Hardware Reference Manual (version 1.10) 8
I/O Summary
High-
Current DIO
(PWM/Relay/
Digital Output
or Input)
[5 or 3.3V]
10
Analog
Inputs
(12-bit
resolution)
[5 or 3.3V]
CAN I2C
(or 2 DO or 2DI
w/pullups)
SPI
(or 3 DO, 1DI)
TTL UART
(or 1 DO, 1DI)
HW Quadrature Decode (Max 5 Pair [10 pins])
PWM/Digital IOs (Max 12)
150mA Analog
Supply Up to 400mA Digital Supply
FlexDIO
12
4
VMX-pi I/O Summary
3.3 V (5V Tolerant
inputs)
• 30 Digital I/O Channels
-FlexDIOsPWM-capable, H/W decode of 5 Quadrature Encoders
-High Current DIOseither all inputs or all PWM-capable outputs
-Comm DIOsPWM-capable outputs, 4 inputs) supporting SPI, I2C
and UART or Digital I/O functions
• 4 Analog Input Channels
• Dedicated CAN Interface
Comm DIO [5 or 3.3V]
Figure 3 VMX-pi IO Summary
FlexDIO Channels: These channels drive 3.3V, are 5V tolerant when used as inputs, and each channel is
individually software configurable as input or output channel. FlexDIO channels have a lower output
current drive than other channel types, and support advanced timer functions including decoding of
signals from quadrature encoders.
High-Current DIO Channels: These channels drive 3.3V or 5V (jumper-configurable), and are jumper-
configurable to be either all inputs or all outputs. High-Current DIO channels provided enhanced
current-drive capabilities allowing them to be used to drive relays as well as motor controllers.
Analog Input Channels: These channels accept 3.3V or 5V input signals.
Comm DIO Channels: These channels drive 3.3V or 5V (jumper-configurable); some are fixed as input
channels, and some are as fixed output channels. These channels support a medium-current drive
capability to support communication across extended distances, subject to the restrictions of each
protocol; these channels are designed to support high-bandwidth communication rates.

VMX-pi Hardware Reference Manual (version 1.10) 9
CAN Interface: The CAN interface supports a positive and negative differential signal pair. NOTE: The
two CAN -pi Channel
 below.
Table 2 VMX I/O Channel Type Summary
Type
Count
S/W
Direction
Select
High
Current/Jumper
Direction Select
Analog
Input
Digital
Comm
FlexDIO
12
Yes
HiCurrDIO
10
Yes
CommDIO
8
Yes
AnalogIn
4
Yes

VMX-pi Hardware Reference Manual (version 1.10) 10
I/O Resource Summary
Each VMX-pi channel can be used for multiple functions. This flexibility functionality is provided by a set
of I/O Resources. Each VMX-pi channel may be routed (under software control) to different I/O
resources, depending upon the VMX-pi application requirements.
Type
Description
Typical Use
Digital Input
Detects current signal digital level
(high/low)
Reading state of a button
Digital Output
Transmits current signal digital level
(high/low)
Triggering a Relay
PWM Generator
Transmits periodic pulses with
configurable period and pulse-width
Controlling a motor or servo
PWM Capture
Measures pulse with (frequency and duty
cycle) of periodic pulses
Reading current pulse width
from servo controller
Interrupt
Generates Interrupts on selected signal
edge transitions
 of an ultrasonic
distance sensor
Accumulator
Performs Oversampling/Averaging on an
Analog Input
Noise-removal and resolution
enhancement on inputs from an
analog potentiometer
Analog Trigger
Generates Interrupts on analog input
high/low level transitions

sensor input
UART
TX/RX line data transceiver
Communication with an
external GPS
SPI
CLK/MOSI/MISO/CS line data transceiver
Communication with an
external IMU sensor
I2C
SCL/SDA line data transceiver
Communication with an
external LIDAR sensor
Table 3 VMX-pi Resource Summary
Many I/O Resource Types support a single I/O Channel; certain Resource Types may support more than
1 channel (e.g., a Quadrature Encoder Resource supports two I/O Channels, one for the A signal and
another for the B signal).
Channel/Resource Routing
To use an I/O Resource, one or more I/O Channels must be routed to the resource. Each I/O Channel
Type may be routed to the following I/O Resources:
Type
DIO/
PWM
Encoder
PWM
Capture
Interrupt
Accumulator
Analog
Trigger
UART
SPI
I2C
# Chan
per
Resource
1
2
1
1
1
1
2
4
2
FlexDIO
Yes
Yes
Yes
Yes
HiCurrDIO
Yes
Yes