User's Manual

P330 Data Sheet / User Guide 23
DRAFT
of a 0.01uF capacitor and 1.0 MegOhm resistor. This mounting hole provides the Chassis Ground.
The position of this hole is shown in Figure 4-1.
4.4 Host to P330 Interface Options
The P330 supports five different host interfaces: USB, Serial, SPI, Ethernet, and CAN. This wide
choice of interfaces provides the user with the freedom to experiment with and to optimize for their
specific application the means by which the overall system (P330 plus the user Host) communicates.
The characteristics of these interfaces are summarized below. For information on pin assignments see
Section 4.2 – Connector Pinouts.
The protocol used to communicate with the P330 is fully defined in the Time Domain RangeNet API
Specifications, various C and MATLAB examples, and in the document “Using the USB and Serial
specifications. All of these resources are provided on the delivery disks and are also available on the
Time Domain website, www.timedomain.com.
4.4.1 USB 2.0 High Speed Device
The P330 supports USB 2.0 High Speed Device connection through the USB Data microUSB jack
(J5). When connecting through J5 it is important to remember that this jack only provides the data
communications lines to the P330. To power the board, the user should apply power to the board
either through the USB Power microUSB jack (J13), through the locking connector (J11) or through
pin 21 on the User Mezzanine connector.
The maximum data rate for the USB is 480 Mbps. However, the maximum effective throughput will
be limited by many factors, including the speed of the Host computer, the specific implementation of
the USB driver, processing overhead at the P330, and processor overhead at the Host computer. The
effective transfer rate is on the order of 5-10% of the maximum data rate.
4.4.2 User Serial
The User Serial interface is RS-232 Universal Asynchronous Receiver/Transmitter (UART) Serial
link operating at 3.3V TTL logic levels. The maximum speed of the interface is 115.2 kbps. Lower
rates of 9.6, 19.2, 38.4, and 57.6 kbps are also supported. The default rate is 115.2 kbps.
However, the maximum rate is largely a function of the ability of the system to drive the cable
capacitance. If a shorter cable is used or if the user provides an external line driver, then the
communications rate can be increased by factors of 2 up to 921.6 kbps. Operation at these higher
ranges is also limited by the serial interface circuit on the user-provided Host computer. The
maximum length of cable must be determined empirically. Time Domain has found that a cable
length of 1 foot (30 cm) or less will support the 460.8 kbps rate quite reliably.
User Serial is provided on the Locking connector (J11), the User Mezzanine connector (J10), and the
User Header (J7).
The Serial interface uses 3.3 volt logic. Do not connect 5 volt serial cables to the P330. In fact, do not
connect any serial cables that operate at greater than 3.3 volts. The increased voltage will physically
damage the P330.