2 Test Setup
VCC is supplied with external power; 3.3 V or 5 V is recommended. The GND header pins are the ground
connection for the TRS3221RGTEVM. The DB9 connector mates with a personal computer's RS-232 port or a
USB to RS-232 adapter. For initial testing, external wires can be added. The ideal usage involves connecting the
terminal block data and control lines to a system that has an UART (Universal asynchronous receiver/
transmitter) onboard.
2.1 Overview and Basic Operation Settings
Transceiver V
CC
power supply (pin 16 of J2) and GND (pin 15 of J2)
: The basic setup of the
TRS3221RGTEVM uses a single 3.3-V or 5-V power supply to evaluate the transceiver’s performance. To power
the transceiver, connect the 3.3-V or 5-V Vcc supply to pin 16 of J2 and GND to pin 15 of J2. The power supplied
should meet the required specification of VCC for the transceiver being tested.
The capacitors installed on the TRS3232RGTEVM were selected for V
CC
= 3.3-V operation. It is required to
change some of the onboard capacitors for 5-V testing (
Table 2-1. Capacitor configuration
C1
C2
C3
C4
3.3V
100nF
100nF
100nF
100nF
5.0V
47nF
330nF
330nF
330nF
(optional) Charge pump output (V+ and V-)
: TRS3221RGT has an internal charge pump circuit to generate
RS-232 signaling (Ref 1). Before starting the communication, the charge pump operation can be checked by
monitoring these two test points.
TIN input (pin 8 of J2)
: Connect the function generator to pin 8 of the J2 header on the board. Set the function
generator to generate a square wave of a certain frequency, 50% duty cycle, the low voltage level to 0 V, and the
high level to 5-V. This clock signal simulates the TTL data from MCU. Alternatively PRBS data from a signal
generator can be transmitted. Please note the data rate is not recommended to be faster than the specification
in the datasheet.
DOUT output (pin 2 of J1)
: Connect an oscilloscope probe to pin 2 of J1 on the board. Setup the oscilloscope
for proper time and voltage per division. Allow room to show three periods of bit-long waveform on the
oscilloscope. The received RS-232 signal should match the transmitted logic data. This indicates that the driver
of TRS3221RGT is operating correctly.
(optional) Loopback
: Connect pin 3 of J1 to pin 2 of J1. By shorting these two pins, the transmitted RS-232
signal is looped back to the receiver of TRS3232RGT. Connect an oscilloscope probe to pin 6 of J2 on the
board. Setup the oscilloscope for proper time and voltage per division. Allow room to show three periods of bit-
long waveform on the oscilloscope. The received TTL signal should match the loopback data. This indicates that
the receiver of TRS3221RGT is operating correctly.
Test Setup
SLLU328 – DECEMBER 2020
TRS3221 EVM User's Guide
3
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