Expansion Hub Guide
–
Rev 4
© REV Robotics, LLC 2017
17
3
INTEGRATED SENSORS
The REV Robotics Expansion Hub integrates a number of feedback sensors on board. Some of these are user accessible
in the latest FTC Android Studio SDK (version 3.1 released May 2017) but others are not yet directly user accessible.
These sensors are in some cases also used the Expansion Hub for internal safety monitoring.
•
Battery Voltage Monitoring [
Accessible in Ver 3.1
]
•
Integrated 9-axis IMU [
Accessible in Ver 3.1
]
o
Bosch BNO055 9-axis absolute orientation sensor
o
Internally connected to I2C port 0 and configured to address 0x28
•
Current Monitoring [Not Available in Ver 3.1]
o
Battery
o
I2C Bus
o
Servo Bus
o
Digital Bus
•
Per Motor Channel Current Monitoring and Control [Not Available in Ver 3.1]
4
LEGACY SENSOR SUPPORT
4.1
Level Shifter
The Expansion Hub is a 3.3V logic level device, but many of the sensor that teams have previously purchased through
companies such as Modern Robotics are 5V logic level devices. Many of these previously purchased sensors can be
used with the new system by using a level shifter device. REV Robotics offers a Level Shifter (REV-31-1389) and an
optional Sensor Adapter Cable (REV-31-1384) so teams can more easily use their legacy sensors with the new
Expansion Hub system.
The REV Robotics Level Shifter is a PCB which generates a 5V output from the 3.3V input and uses a MOSFET on each
signal line to create a bidirectional communication appropriate for a variety of digital signals include I2C communication
(Figure 5). For more information on how bidirectional level shifting communication is accomplished, please reference
the
NXP Application Note AN10441
.
Figure 5: 3.3V to 5V Level Shifter Board
