REV Robotics RIOduino, User Manual

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REV
-11-1104
-UM-00 Copyright © 2014 REV Robotics, LLC 7
2.3.1 SHARED I
2
C
Table 2-4 shows which signals are shared for I
2
C.
Table 2-4 Shared I
2
C Signals
RIOduino Signal RIOduino Shield Pin MXP Pin MXP Signal
AD4/SDA J3.5 J1.34 DIO15/I2CSDA
AD5/SCL J3.6 J1.32 DIO14/I2CSCL
As with any I
2
C bus, pull-up resistors are required for both SCL and SDA. To keep AD4 and AD5 free for analog use, the
RIOduino has two unpopulated positions (R12, R13) for 2.2 kΩ 0603 surface mount resistors. When used with the
roboRIO, these external resistors are not needed because the roboRIO has internal pull-up resistors. For other
applications, these resistors can be added. Please see APPENDIX A SCHEMATIC and APPENDIX B DRAWING for the
schematic and component placement drawing.
2.3.2 SHARED UART
Table 2-5 shows which signals are shared for UART.
Table 2-5 Shared UART Signals
RIOduino Signal RIOduino Shield Pin MXP Pin MXP Signal
IO0/RX J5.1 J1.14 UART.TX
IO1/TX J5.2 J1.10 UART.RX
CAUTION
The UART signals are at TTL levels. Do not connect directly to a RS-232 serial port without an RS-232 to TTL converter.
The UART on the ATmega328 is connected to both the MXP connector and the on-board USB to Serial converter through
1 kΩ resistors. These resistors prevent either the roboRIO or the USB to Serial converter from forcibly driving the bus
when another UART device is connected through the shield headers.
2.4 WS281x RGB LED STRIP CONNECTIONS
A popular application for Arduino-compatible boards like the RIOduino is to control addressable RGB LED strips like the
WS2811 and WS2812 based strips. The RIOduino includes five plated-through holes that make it easy to connect one of
these strips and its external power source. Figure 2-2 shows how to wire a WS281x LED strip with an external 5V supply.