1-10
|
ni.com
Chapter 1
Fixed Behavior Signals
Supporting Onboard USB Devices
When you implement a USB device directly on your carrier board, you can connect the device
to a USB Host port from the sbRIO-9651 SOM. For this case, use the following design
guidelines:
•
You can connect the USB data pair directly to a USB device on your carrier board.
•
A current limiter is not required.
•
Use the CARRIER_RST# signal to reset the USB device when the sbRIO-9651 SOM is in
reset.
•
Tie the USB
x
_VBUS signal to 3.3 V or 5 V.
USB Routing Considerations
NI recommends the following design practices for properly routing USB signals on your carrier
board:
•
Route the USB
x
_DP and USB
x
_DN signals as differential pairs with 90
Ω
differential
impedance.
•
Length-match the positive and negative signal for each USB data pair to within 10 mils.
•
Limit the USB
x
_DP and USB
x
_DN trace lengths on the carrier board to 8.0 in. or less,
which is the length at which USB compliance was tested.
UART/Console Out (Serial1)
The sbRIO-9651 SOM provides a dedicated UART (Serial1) interface for use on a carrier board.
This interface also functions as an operating system console when Console Out is enabled. Refer
to the
Additional RS-232 (Serial2, Serial3, Serial4)
and
sections of
, for information about implementing additional serial
ports.
Serial1 Signal Definitions
Table 1-10 describes the Serial1 port pins and signals on the sbRIO-9651 SOM connector.
Note
The NI-Serial driver has been developed for and tested with the Texas
Instruments TRS3253EIRSMR RS-232 transceiver. Other transceivers may be
compatible.