Texas Instruments XTR108EVM-USB User manual

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XTR108EVM-USB Evaluation Board and Software Tutorial
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User's Guide
SBOU123A–March 2012–Revised September 2016
XTR108EVM-USB Evaluation Board and Software Tutorial
This user's guide describes the characteristics, operation and use of the XTR108EVM-USB evaluation
module (EVM). This EVM is designed to evaluate the performance of the XTR108, an SPI™-
programmable, current- or voltage-output, two-wire transmitter designed for temperature and bridge
sensors. Throughout this document, the terms evaluation board,evaluation module, and EVM are
synonymous with the XTR108EVM-USB. This user's guide also includes information regarding operating
procedures and input/output connections, an electrical schematic, printed circuit board (PCB) layout
drawings, and a parts list for the EVM.
Contents
1 Overview...................................................................................................................... 4
2 Hardware Overview.......................................................................................................... 6
3 Hardware Setup ............................................................................................................ 16
4 Software Setup ............................................................................................................. 25
5 Software Overview......................................................................................................... 26
6 General Operating Tips.................................................................................................... 47
7 Hardware Documentation ................................................................................................. 48
8 Appendix..................................................................................................................... 52
List of Figures
1 Hardware Included With the XTR108EVM-USB......................................................................... 5
2 XTR108EVM-USB Hardware Setup....................................................................................... 6
3 XTR108EVM-USB Block Diagram......................................................................................... 7
4 XTR108EVM-USB Interface Board Connectors and Jumpers......................................................... 8
5 XTR108EVM-USB Sensor Board Connectors and Jumpers......................................................... 13
6 Pin Socket Mechanical Description...................................................................................... 16
7 Connecting the USB DAQ Platform to the XTR108EVM-USB Interface Board.................................... 17
8 All Boards Connected ..................................................................................................... 17
9 Connecting Power to the USB DAQ Platform.......................................................................... 18
10 Connecting the USB Cable to the USB DAQ Platform................................................................ 19
11 Found New Hardware Pop-up Message................................................................................ 19
12 Connecting a Loop Power Supply to the XTR108EVM-USB Interface Board ..................................... 20
13 34401A Multimeter Connections ......................................................................................... 21
14 USB DAQ Platform Default Jumper Settings........................................................................... 22
15 XTR108EVM-USB Interface Board Default Jumper Settings ........................................................ 23
16 XTR108EVM-USB Sensor Board Default Jumper Settings .......................................................... 24
17 Starting the XTR108EVM-USB Software ............................................................................... 25
18 XTR108EVM-USB Software Start-up, Block Diagram Tab........................................................... 26
19 USB Communication Error................................................................................................ 27
20 XTR108EVM-USB Software, Find Resistors Tab...................................................................... 32
21 RSET Error.................................................................................................................... 34
22 Linearity Warning........................................................................................................... 34

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23 Save Model File ............................................................................................................ 35
24 XTR108EVM-USB Software, Manual Calibration Tab ................................................................ 36
25 Adjust RTD Emulator ...................................................................................................... 37
26 Manual Calibration Tab, Post-Calibration............................................................................... 39
27 XTR108EVM-USB Software, Automatic Calibration Tab ............................................................. 40
28 Automatic Calibration Tab, Post-Calibration............................................................................ 42
29 XTR108EVM-USB Software, Registers Tab............................................................................ 43
30 GPIO Control Window..................................................................................................... 45
31 Debug Window ............................................................................................................. 46
32 About Window .............................................................................................................. 46
33 Discrete Charge Pump on Sensor Interface Board.................................................................... 47
34 XTR108EVM-USB Interface Board Schematic......................................................................... 48
35 XTR108EVM-USB Sensor Board Schematic........................................................................... 49
36 XTR108 Input MUX Example (TMIN = –200°C, PT100 RTD).......................................................... 52
37 XTR108 Input MUX Example (TMAX = +850°C, PT100 RTD) ......................................................... 53
38 XTR108 Input MUX Example (TMAX = +850°C, PT1000 RTD)........................................................ 53
39 RSET Circuitry ................................................................................................................ 54
40 RLIN Circuitry................................................................................................................. 54
41 Linearity Correction Method .............................................................................................. 55
42 Linearity Improvement..................................................................................................... 55
List of Tables
1 XTR108EVM-USB Kit Contents ........................................................................................... 5
2 Related Documentation..................................................................................................... 6
3 Multimeter Connect Pinout ................................................................................................ 9
4 J1 Pinout (15-Pin Female DSUB) ......................................................................................... 9
5 J2 Pinout (Vo_XTR108)..................................................................................................... 9
6 J3 Pinout (Io_XTR108) .................................................................................................... 10
7 J4 Pinout (Loop Supply)................................................................................................... 10
8 J5 Pinout (25-Pin Female DSUB)........................................................................................ 10
9 J6 Pinout (25-Pin Male DSUB)........................................................................................... 11
10 J7 Pinout (SPI) ............................................................................................................. 11
11 J8 Pinout (RTD_CON)..................................................................................................... 12
12 Interface Board Jumper Functions....................................................................................... 12
13 J1 Pinout (SPI) ............................................................................................................. 14
14 J3 Pinout (Io_XTR108) .................................................................................................... 14
15 J4 Pinout (Vo_XTR108)................................................................................................... 14
16 J5 Pinout (RTD_CON)..................................................................................................... 14
17 Sensor Board Jumper Functions......................................................................................... 15
18 XTR108EVM-USB Interface Board Default Jumper Settings ........................................................ 23
19 XTR108EVM-USB Sensor Board Default Jumper Settings .......................................................... 25
20 PGA Gain, Loop Transconductance, and Input Full-Scale Differential Voltage.................................... 28
21 Equations for Calculating Zero Output .................................................................................. 28
22 Equations for Calculating IREF Current ................................................................................... 29
23 Overscale Threshold....................................................................................................... 30
24 Underscale Threshold ..................................................................................................... 30
25 Alarm Configuration Register............................................................................................. 31
26 Standard RTD Equations.................................................................................................. 33
27 Control Bits Functions ..................................................................................................... 45

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28 XTR108EVM-USB Interface Board Bill of Materials................................................................... 50
29 XTR108EVM-USB Sensor Board Bill of Materials..................................................................... 51
30 Standard RTD Equations.................................................................................................. 56
31 Mnemonic Commands..................................................................................................... 59
32 SPI Modes of Operation................................................................................................... 60
33 General USB-DAQ Commands .......................................................................................... 60

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1 Overview
This document provides the information needed to set up and operate the XTR108EVM-USB evaluation
module, which is a test platform for the XTR108 programmable two-wire transmitter and sensor
conditioner. For a more detailed description of the XTR108, refer to the product data sheet (SBOS187)
available from the Texas Instruments web site at www.ti.com.
The XTR108EVM-USB is an evaluation module that is used to fully evaluate the XTR108. The XTR108 is
an integrated circuit that provides correction of zero, span, and linearization errors for RTDs (resistive
thermal devices) and bridge sensors. Overall system accuracy of 0.1% error (relative to full-scale output
span) or less is easily achievable using a two-point calibration algorithm. The XTR108EVM-USB consists
of three PCBs. One board (the USB DAQ Platform) generates the digital signals required to communicate
with the XTR108. The second board (XTR108EVM-USB Interface Board) provides a convenient interface
to standard multimeters and includes an onboard RTD emulator circuit to facilitate calibration. The third
board (XTR108EVM-USB Sensor Board) contains the XTR108 device as well as support and
configuration circuitry. Once calibrated, the XTR108EVM-USB Sensor Board can be used as a fully-
functional, stand-alone system. Similarly, the USB-DAQ Platform and XTR108EVM-USB Interface Board
can be connected to other stand-alone XTR108 circuitry for quick calibration, making the XTR108EVM-
USB a capable production tool.

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1.1 XTR108EVM-USB Kit Contents
Figure 1 shows the hardware included with the XTR108EVM-USB kit. Table 1 describes each item
included in the kit. Contact the Texas Instruments Product Information Center nearest you if any
component is missing. It is highly recommended that you also check the XTR108 product folder to verify
that you have the latest version of the related software.
Figure 1. Hardware Included With the XTR108EVM-USB
Table 1. XTR108EVM-USB Kit Contents
Quantity Item Description
1 USB DAQ Platform Digital communications board
1 XTR108EVM-USB Interface Board XTR108EVM-USB Interface Board with required populated components
1 XTR108EVM-USB Sensor Board XTR108EVM-USB Sensor Board with required populated components
1 USB cable Connects PC to USB DAQ Platform
1 Power Cable Connects external supply to USB DAQ Platform

x
x
x
x
x
Windows PC HP/Agilent 34401A DMM
+24-V Power Supply
USB Cable
+6-V to +9-V Power Supply
XTR108EVM-USB
Interface Board XTR108EVM-USB Sensor Board
USB DAQ
Platform
HI(F) LO(F) HI(S) LO(S) I(F)
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1.2 Related Documentation from Texas Instruments
The documents listed in Table 2 provide information regarding Texas Instruments' hardware used in
assembly of the XTR108EVM-USB. This user's guide is available from the TI web site under literature
number SBOU123. Any letter appended to the literature number corresponds to the document revision
that is current at the time of the writing of this document. Newer revisions may be available from the TI
web site at www.ti.com, or contact the Texas Instruments Product Information Center. Identify the
document by both title and literature number.
Table 2. Related Documentation
Document Literature Number
USB DAQ Platform user's guide SBOU056
XTR108 product data sheet SBOS187
2 Hardware Overview
Figure 2 shows the XTR108EVM-USB system setup. The Windows™ PC runs software that
communicates with the USB DAQ Platform. The USB DAQ Platform generates the digital signals used to
communicate with the XTR108. The XTR108EVM-USB Interface Board routes digital communication and
analog input signals to the XTR108, provides a convenient interface to standard multimeters, and includes
an onboard RTD emulator circuit to facilitate calibration. The XTR108EVM-USB Sensor Board contains
the XTR108 device as well as support and configuration circuitry.
Figure 2. XTR108EVM-USB Hardware Setup

XTR108EVM-USB
Interface Board XTR108EVM-USB Sensor Board
25-pin
DSUB
from
USB
DAQ
25-pin
DSUB
from
USB
DAQ
15-pin
DSUB XTR108
RTD
Emulator
Signal
Routing
Circuit
Digital Multimeter
Interface
External Device
Connections
Control Signals
5.0V Power Supply
SPI Interface
EEPROM
Loop Supply
Connection
RTD
Connection
Loop Supply
SPI Interface
RTD Emulator
External Device
Connections
Current/Voltage Output
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2.1 XTR108EVM-USB Theory of Operation
Figure 3 shows the block diagram of the XTR108EVM-USB Interface Board and Sensor Board.
Figure 3. XTR108EVM-USB Block Diagram
The XTR108EVM-USB Interface Board provides connections to the SPI interface and 5.0-V power supply
on the USB DAQ Platform and also provides a convenient interface to an external digital multimeter
(DMM). The Interface Board also contains a network of signal-controlled relays from the USB DAQ that
handles the routing of all EVM input and output signals.
The Interface Board also includes a user-configurable RTD emulator circuit that simulates the behavior of
a RTD (resistive thermal device) using potentiometers and surface-mount resistors. Using the RTD
emulator allows the user to more quickly achieve a deeper understanding of the XTR108EVM-USB
hardware and software. When the XTR108EVM-USB capabilities and functions are fully understood, the
user can connect a real-world sensor to the EVM and perform a full calibration. Note that calibrations with
real-world sensors are time-consuming because devices such as these are normally calibrated at multiple
temperatures in an environmental chamber. It is not unusual for temperature calibration to require 12
hours.
The XTR108EVM-USB Sensor board contains the XTR108 device as well as support and configuration
circuitry. The configuration circuitry includes a 4Kb EEPROM used to store the XTR108 power-on settings.
When the XTR108 is powered on it automatically reads the EEPROM and programs its internal registers
with the values stored in the EEPROM.

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2.2 Interface Board Overview
Figure 4 shows the location of all XTR108EVM-USB Interface Board connectors and jumpers.
Figure 4. XTR108EVM-USB Interface Board Connectors and Jumpers

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2.2.1 Interface Board: Signal Definitions and Pinouts
This section provides the signal definitions for all XTR108EVM-USB Interface Board connectors.
2.2.1.1 Multimeter Connect
Table 3 shows the signals connected to the Multimeter Connect interface on the Interface Board.
Table 3. Multimeter Connect Pinout
Name Description
HI(F) Voltage and resistance measurement; high-side forced connection
LO(F) Voltage and resistance measurement; low-side forced connection
HI(S) Voltage and resistance measurement; high-side sensed connection
LO(S) Voltage and resistance measurement; low-side sensed connection
I(F) Current output measurement connection
2.2.1.2 J1 (15-Pin Female DSUB)
Table 4 shows the signals connected to J1 on the Interface Board. J1 is the connection for all input and
output signals between the Interface Board and Sensor Board.
Table 4. J1 Pinout (15-Pin Female DSUB)
Pin Name Description
1 SPI_DIO SPI data input/output
2 SPI_SCK SPI clock
3 SPI_CS1 SPI chip select
4 RCM RCM (common-mode resistor)
5 RZ RZ(zero-scale resistor)
6 RTD RTD resistance
7 IO– Low-side current output from the XTR108
8 IO+ High-side current output from the XTR108
9 VO– Low-side voltage output from the XTR108
10 VO+ High-side voltage output from the XTR108
11 GND Ground
12-15 NC No connection
2.2.1.3 J2 (Vo_XTR108)
Table 5 shows the signals connected to J2 on the Interface Board. J2 is used to connect the voltage
output of an external XTR108 system to the Interface Board.
Table 5. J2 Pinout (Vo_XTR108)
Pin Name Description
1 VO+ High-side voltage output from the XTR108
2 VO– Low-side voltage output from the XTR108

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2.2.1.4 J3 (Io_XTR108)
Table 6 shows the signals connected to J3 on the Interface Board. J3 is used to connect the current
output of an external XTR108 system to the Interface Board.
Table 6. J3 Pinout (Io_XTR108)
Pin Name Description
1 IO+ High-side current output from the XTR108
2 IO– Low-side current output from the XTR108
2.2.1.5 J4 (Loop Supply)
Table 7 shows the signals connected to J4 on the Interface Board. J4 provides the loop power supply to
the XTR108.
Table 7. J4 Pinout (Loop Supply)
Pin Name Description
1 LOOP– Low-side loop power supply
2 LOOP+ High-side loop power supply
2.2.1.6 J5 (25-Pin Female DSUB)
Table 8 shows the signals connected to J5 on the Interface Board. J5 is used to connect the USB DAQ
control signals to the Interface Board.
Table 8. J5 Pinout (25-Pin Female DSUB)
Pin Name Description Used
1 NC No connection No
2 CTRL1 Control signal 1 Yes
3 CTRL2 Control signal 1 Yes
4 CTRL3 Control signal 1 Yes
5 CTRL4 Control signal 1 Yes
6 CTRL5 Control signal 1 Yes
7 CTRL6 Control signal 1 Yes
8 CTRL7 Control signal 1 Yes
9 CTRL8 Control signal 1 Yes
10 MEAS1 Measure input 1 No
11 MEAS2 Measure input 1 No
12 MEAS3 Measure input 1 No
13 MEAS4 Measure input 1 No
14 MEAS5 Measure input 1 No
15 MEAS6 Measure input 1 No
16 MEAS7 Measure input 1 No
17 MEAS8 Measure input 1 No
18 SPI_SCK SPI clock, channel 2 No
19 SPI_CS2 SPI chip select, channel 2 No
20 SPI_DOUT2 SPI data output, channel 2 No
21 SPI_DIN2 SPI data input, channel 2 No
22 VDUT Switched power supply No
23 VCC USB DAQ power supply No
24, 25 GND Ground No

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2.2.1.7 J6 (25-Pin Male DSUB)
Table 9 shows the signals connected to J6 on the Interface Board. J6 is used to connect the SPI interface
and 5.0-V power supply from the USB DAQ to the Interface Board.
Table 9. J6 Pinout (25-Pin Male DSUB)
Pin Name Description Used
1 DAC_A DAC_A output No
2 DAC_B DAC_B output No
3 DAC_C DAC_C output No
4 DAC_D DAC_D output No
5 ADS1_VIN+ ADS1 positive input No
6 ADS1_VIN– ADS1 negative input No
7 ADS2_VIN+ ADS2 positive input No
8 ADS2_VIN– ADS2 negative input No
9 I2C_SCK I2C clock No
10 I2C_SDA I2C data No
11 ONE_WIRE One-wire communication line No
12 I2C_SDA_ISO I2C data (isolated) No
13 I2C_SCK_ISO I2C clock (isolated) No
14 XTR +LOOP Current-loop high-side input No
15 XTR –LOOP Current-loop low-side input No
16 INA– INA negative input No
17 VDUT Selectable 3.3-V or 5.0-V power supply No
18 VCC 5.0-V power supply Yes
19 +15V +15-V power supply No
20 –15V –15-V power supply No
21 GND Ground Yes
22 SPI_SCK SPI clock, channel 1 Yes
23 SPI_CS1 SPI chip select, channel 1 Yes
24 SPI_DOUT SPI data output, channel 1 Yes
25 SPI_DIN1 SPI data input, channel 1 Yes
2.2.1.8 J7 (SPI)
Table 10 shows the signals connected to J7 on the Interface Board. J7 is used to connect the SPI
interface to an external XTR108 system.
Table 10. J7 Pinout (SPI)
Pin Name Description
1 DIO SPI data input/output
2 SCK SPI clock
3 CS1 SPI chip select

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2.2.1.9 J8 (RTD_CON)
Table 11 shows the signals connected to J8 on the Interface Board. J8 is used to connect the RTD
emulator circuit to an external XTR108 system.
Table 11. J8 Pinout (RTD_CON)
Pin Name Description
1 RCM RCM (common-mode resistor)
2 RZ RZ(zero-scale resistor)
3 RTD RTD resistance
2.2.2 Interface Board Jumper Settings
Table 12 explains the function of the XTR108EVM-USB Interface Board jumpers.
Table 12. Interface Board Jumper Functions
Jumper Default Description
JMP1 POT_RTD This jumper selects which resistor string is used for the RTD emulator minimum-scale output.
Set the jumper to the POT_RTD position to use potentiometers POT1 and POT2. Set the
jumper to the R_RTD position to use surface-mount resistors R22-R24 (not installed by
default).
JMP2 POT_RTD This jumper selects which resistor string is used for the RTD emulator mid-scale output.
Set the jumper to the POT_RTD position to use potentiometers POT3 and POT4. Set the
jumper to the R_RTD position to use surface-mount resistors R25-R27 (not installed by
default).
JMP3 POT_RTD This jumper selects which resistor string is used for the RTD emulator maximum-scale output.
Set the jumper to the POT_RTD position to use potentiometers POT5 and POT6. Set the
jumper to the R_RTD position to use surface-mount resistors R28-R30 (not installed by
default).

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2.3 Sensor Board Overview
Figure 5 shows the location of all XTR108EVM-USB Sensor Board connectors and jumpers.
Figure 5. XTR108EVM-USB Sensor Board Connectors and Jumpers

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2.3.1 Sensor Board Connections
This section provides signal definitions for all XTR108EVM-USB Interface Board connectors.
2.3.1.1 J1 (SPI)
Table 13 shows the signals connected to J1 on the Sensor Board. J1 is used to connect an external SPI
interface to the Sensor Board.
Table 13. J1 Pinout (SPI)
Pin Name Description
1 CS1 SPI chip select
2 SCK SPI clock
3 SDIO SPI data input/output
2.3.1.2 J2 (15-pin Male DSUB)
J2 is the connection for all input and output signals between the Interface Board and Sensor Board. See
Table 4 for pinout information.
2.3.1.3 J3 (Io_XTR108)
Table 14 shows the signals connected to J3 on the Sensor Board. J3 is used to connect an external loop
power supply to the Sensor Board and to connect the XTR108 current output to an external ammeter.
Table 14. J3 Pinout (Io_XTR108)
Pin Name Description
1 IO– Low-side loop power-supply and current output from the XTR108
2 IO+ High-side loop power-supply and current output from the XTR108
2.3.1.4 J4 (Vo_XTR108)
Table 15 shows the signals connected to J4 on the Sensor Board. J4 is used to connect the XTR108
voltage output to an external voltmeter.
Table 15. J4 Pinout (Vo_XTR108)
Pin Name Description
1 VO+ High-side voltage output from the XTR108
2 VO– Low-side voltage output from the XTR108
2.3.1.5 J5 (RTD_CON)
Table 16 shows the signals connected to J5 on the Sensor Board. J5 is used to connect an external RTD
to the Sensor Board.
Table 16. J5 Pinout (RTD_CON)
Pin Name Description
1 RTD RTD resistance. Connect the red wire of a two- or three-wire RTD here.
2 RZ RZ(zero-scale resistor). Connect the black wire of a two- or three-wire RTD here.
3 RCM RCM (common-mode resistor). Short to pin 2 (RZ) if using a two-wire RTD. Connect the second
black wire here if using a three-wire RTD.

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2.3.2 Sensor Board Jumper Settings
Table 17 explains the function of the XTR108EVM-USB Interface Board jumpers.
Table 17. Sensor Board Jumper Functions
Jumper Default Description
JMP1 FET This jumper selects whether to enable or bypass the depletion-mode transistor Q1. Set the jumper to the FET position when using current-output mode. Set the jumper to the
BYPASS position when using voltage-output mode.
JMP2 FET This jumper selects whether to enable or bypass the depletion-mode transistor Q1. Set the jumper to the FET position when using current-output mode. Set the jumper to the
BYPASS position when using voltage-output mode.
JMP3 IOUT This jumper selects between current-output mode or voltage-output mode. Set the jumper to the IOUT position when using current-output mode. Set the jumper to the
VOUT position when using voltage-output mode.
JMP4 NO LOAD This jumper selects whether to connect or disconnect a load resistor (RL, not installed by
default) from the voltage output of the XTR108.
Set the jumper to the NO LOAD position when using current-output mode. Set the jumper to
the LOAD position when using voltage-output mode (optional).
JMP5 IOUT This jumper selects between the current-output or voltage-mode charge pump input at the
XTR108 I_IN pin.
Set the jumper to the IOUT position when using current-output mode. Set the jumper to the
CP position when using voltage-output mode.
JMP6 BYPASS This jumper enables or disables the SPI clock buffer in the voltage-output mode charge pump. Set the jumper to the BYPASS position when using current-output mode. Set the jumper to
the BUF position when using voltage-output mode.
JMP7 NO CLK This jumper enables or disables the voltage-output mode charge pump. Set the jumper to the NO CLK position when using current-output mode. Set the jumper to the
CP SCK position when using voltage-output mode.
JMP8 2-WIRE This jumper selects what type of RTD is connected to the XTR108.
Set the jumper to the 2-WIRE position when using the RTD emulator on the Interface Board
or when connecting an external two-wire RTD. Set the jumper to the 3-WIRE position when
connecting an external three-wire RTD.

Through-hole lead
makes contact to
pin socket with
spring action.
PIN DIA
0.36 - 0.56
[.014 - .022]
SPRING
EYELET
6.60
[.260]
2.54
[.100]
CONTACT PT
MIN
6.27
[.247] MAX PIN LENGTH
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2.3.3 Test Points and Miscellaneous Breadboard Area
There are multiple points available on the Sensor Board, including several connections to IRET. IRET is
common (labeled as GND on the board) for most XTR108 applications, and is provided for ease of
measuring analog signals. Reserved areas with plated-through, standard-spacing, 0.1-inch holes for
miscellaneous proof-of-concept breadboarding are also provided on the board. Most of the surface-mount
components have pin sockets associated with them. These pin sockets allow the replacement of a
surface-mount component with a through-hole component.
The pin sockets provide good contact with the leads of a component without solder, thus enabling quick
reconfiguration of the board for many different XTR108 designs, as shown in Figure 6.
Figure 6. Pin Socket Mechanical Description
3 Hardware Setup
The XTR108EVM-USB hardware setup involves connecting the three EVM boards together, applying
power to the USB DAQ platform, connecting the USB cable, applying power to the Interface Board, and
setting the jumpers. This section covers the details of this procedure.
3.1 Electrostatic Discharge Warning
CAUTION
Many of the components on the XTR108EVM-USB are susceptible to damage
by electrostatic discharge (ESD). Customers are advised to observe proper
ESD handling precautions when unpacking and handling the EVM, including
the use of a grounded wrist strap at an approved ESD workstation.

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3.2 Connecting the Hardware
When first setting up the EVM hardware, It is recommended to first connect the USB DAQ Platform to the
XTR108EVM-USB Interface Board. To connect the two PCBs together, gently push on both sides of the
25-pin D-SUB connectors as shown in Figure 7. Make sure that the connectors are completely pushed
together because loose connections may cause intermittent operation.
Figure 7. Connecting the USB DAQ Platform to the XTR108EVM-USB Interface Board
Next, connect the XTR108EVM-USB Sensor Board to the XTR108EVM-USB Interface Board by gently
pushing on both sides of the 15-pin DSUB connector. Once the XTR108EVM-USB Sensor Board is
connected, the system looks like the one in Figure 8.
Figure 8. All Boards Connected

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XTR108EVM-USB Evaluation Board and Software Tutorial
3.3 Connecting Power and USB to the USB DAQ Platform
After the three XTR108EVM-USB boards are connected, connect a 6Vdc to 9Vdc power supply to J5 or
T3 of the USB DAQ platform. A power cable is included that fits J5. Caution: Be sure to observe correct
polarity. If connected properly, the µC OK, 3.3-V, and VCC LEDs on the USB DAQ illuminate as shown in
Figure 9. Always connect power before connecting the USB cable. If you connect the USB cable before
connecting the power, the computer attempts to communicate with an unpowered device that is unable to
respond.
Figure 9. Connecting Power to the USB DAQ Platform

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XTR108EVM-USB Evaluation Board and Software Tutorial
Once power has been applied to the USB DAQ Platform, you can connect one end of the USB cable to
the USB DAQ and the other end to a PC USB port, as shown in Figure 10.Figure 11 shows the typical
response to connecting the USB DAQ Platform to a PC USB port for the first time. Typically, the computer
responds with a Found New Hardware,USB Device pop-up message. The pop-up message typically
changes to Found New Hardware,USB Human Interface Device shortly after. This message indicates
that the device is ready to be used. The USB DAQ Platform uses the Human Interface Device drivers that
are part of the Microsoft® Windows® operating system.
In some cases, the Windows Add Hardware Wizard pops up. If this prompt occurs, allow the system
device manager to install the Human Interface Device drivers by clicking Yes when requested to install the
drivers.
Figure 10. Connecting the USB Cable to the USB DAQ Platform
Figure 11. Found New Hardware Pop-up Message

Connect DC Lab
Power Supply to J4 IOUT Mode: 12V to 24V VOUT Mode: 3V to 5.5V
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XTR108EVM-USB Evaluation Board and Software Tutorial
3.4 Connecting Loop Power Supply to the XTR108EVM-USB Interface Board
Connect a dc lab power supply to J4 on the Interface Board as shown in Figure 12. When operating in
current-output mode, the loop-supply input voltage range is 12 V to 24 V. In general, you must consider
the power dissipated in the external transistor and the operating temperature of the transistor in order to
determine the maximum loop voltage and current. This calculation is determined in the XTR108 data
sheet. When operating in voltage-output mode, the loop-supply input voltage range is (3.0 V to 5.5 V) +
VD1.
Figure 12. Connecting a Loop Power Supply to the XTR108EVM-USB Interface Board