Measurement Computing USB-231-OEM User manual

USB-231-OEM
Analog and Digital I/O
User's Guide
January 2019. Rev 4
© Measurement Computing Corporation

2
HM USB-231-OEM.docx
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Other product and company names mentioned herein are trademarks or trade names of their respective
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© 2019 Measurement Computing Corporation. All rights reserved. No part of this publication may be
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photocopying, recording, or otherwise without the prior written permission of Measurement Computing
Corporation.
Notice
Measurement Computing Corporation does not authorize any Measurement Computing Corporation product for
use in life support systems and/or devices without prior written consent from Measurement Computing
Corporation. Life support devices/systems are devices or systems that, a) are intended for surgical implantation
into the body, or b) support or sustain life and whose failure to perform can be reasonably expected to result in
injury. Measurement Computing Corporation products are not designed with the components required, and are
not subject to the testing required to ensure a level of reliability suitable for the treatment and diagnosis of
people.

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Table of Contents
Preface
About this User's Guide .......................................................................................................................5
What you will learn from this user's guide .........................................................................................................5
Conventions in this user's guide .........................................................................................................................5
Where to find more information .........................................................................................................................5
Chapter 1
Introducing the USB-231-OEM.............................................................................................................6
Functional block diagram ...................................................................................................................................7
Chapter 2
Installing the USB-231-OEM.................................................................................................................8
Unpacking...........................................................................................................................................................8
Installing the software ........................................................................................................................................8
Installing the hardware .......................................................................................................................................8
Installing on a Windows platform..................................................................................................................................... 8
Installing on an Android platform..................................................................................................................................... 8
Calibrating the hardware.....................................................................................................................................8
Chapter 3
Functional Details .................................................................................................................................9
Analog input acquisition modes .........................................................................................................................9
Software paced mode........................................................................................................................................................ 9
Hardware paced mode....................................................................................................................................................... 9
Board components ............................................................................................................................................10
USB connector.................................................................................................................................................................10
Header connector J2.........................................................................................................................................................10
Signal connections............................................................................................................................................11
Analog input ....................................................................................................................................................................11
Analog output ..................................................................................................................................................................13
Digital I/O........................................................................................................................................................................15
Trigger input ....................................................................................................................................................................16
Counter input ...................................................................................................................................................................16
USB signals, power (D–, D+, VBUS)..............................................................................................................................16
Status LED driver (LED) .................................................................................................................................................16
+VO power source ...........................................................................................................................................................17
Ground.............................................................................................................................................................................18
Mechanical drawings........................................................................................................................................19
Chapter 4
Specifications......................................................................................................................................20
Analog input .....................................................................................................................................................20
Absolute accuracy (analog input DC voltage measurement accuracy) ............................................................................20
Analog output ...................................................................................................................................................21
Timebase...........................................................................................................................................................21
Digital input/output...........................................................................................................................................21
Digital input.....................................................................................................................................................................22
Digital output...................................................................................................................................................................22
External digital trigger......................................................................................................................................22
Counter .............................................................................................................................................................22
LED electrical characteristics ...........................................................................................................................23
Memory ............................................................................................................................................................23
Power requirements ..........................................................................................................................................23

USB-231-OEM User's Guide
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Power output.....................................................................................................................................................23
USB specifications ...........................................................................................................................................23
Environmental ..................................................................................................................................................24
Mechanical .......................................................................................................................................................24
Header connectors ............................................................................................................................................24
Differential mode pinout..................................................................................................................................................24
Single-ended mode pinout ...............................................................................................................................................25

5
Preface
About this User's Guide
What you will learn from this user's guide
This user's guide describes the Measurement Computing USB-231-OEM data acquisition device and lists
device specifications.
Conventions in this user's guide
For more information
Text presented in a box signifies additional information related to the subject matter.
Caution! Shaded caution statements present information to help you avoid injuring yourself and others,
damaging your hardware, or losing your data.
bold text Bold text is used for the names of objects on a screen, such as buttons, text boxes, and check boxes.
italic text Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase.
Where to find more information
Additional information about USB-231-OEM hardware is available on our website at www.mccdaq.com. You
can also contact Measurement Computing Corporation with specific questions.
Knowledgebase: kb.mccdaq.com
Tech support form: www.mccdaq.com/support/support_form.aspx
Email: [e-mail]
Phone: [phone] and follow the instructions for reaching Tech Support
For international customers, contact your local distributor. Refer to the International Distributors section on our
website at www.mccdaq.com/International.

6
Chapter 1
Introducing the USB-231-OEM
The USB-231-OEM is a USB 2.0 high-speed data acquisition board that provides the following features:
Eight single-ended (SE) or four differential (DIFF) 16-bit analog inputs
50 kS/s maximum sample rate
Two analog outputs with 5 kS/s simultaneous update rate per channel maximum
Eight individually configurable digital I/O channels
32-bit counter
Digital trigger input
User voltage output
One 34-pin header connector for field wiring connections
The USB-231-OEM is a USB 2.0 high speed device that is compatible with USB 3.0 ports. The device is also
compatible with USB 1.1 ports, but use with this older hardware is not recommended due to longer initialization
times that can occur when the USB-231-OEM is connected through USB 1.1 ports or hubs.
The USB-231-OEM is powered by the +5 V USB supply from your computer; no external power is required.
Caution! There are no product safety, electromagnetic compatibility (EMC), or CE marking compliance
claims made for the USB-231-OEM. The USB-231-OEM is intended for use as a component of a
larger system. MCC can help developers meet their compliance requirements. The end product
supplier, however, is responsible for conforming to any and all compliance requirements.

USB-231-OEM User's Guide Introducing the USB-231-OEM
7
Functional block diagram
Device functions are illustrated in the block diagram shown here.
Figure 1. USB-231-OEM functional block diagram

8
Chapter 2
Installing the USB-231-OEM
Unpacking
As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the board from its packaging, ground yourself using a wrist strap or by simply
touching the computer chassis or other grounded object to eliminate any stored static charge.
Installing the software
Refer to the USB-231-OEM product page on the Measurement Computing website for information about how
to install the supported software.
Install the software before you install the hardware
The driver needed to run the device is installed when you install the software. Therefore, you need to install the
software package you plan to use before you install the hardware.
Installing the hardware
Installing on a Windows platform
Connect the USB-231-OEM to a to an available USB port on the computer running Windows. Connect the
other end of the cable to the micro-USB connector on the device. No external power is required.
When connected for the first time, a Found New Hardware dialog opens when the operating system detects the
device. When the dialog closes, the installation is complete.
Installing on an Android platform
Many Android devices include a standard A-type USB port to connect to the USB-231-OEM. If your device
does not have a USB port, you may need a USB OTG cable for your Android device to host a USB device.
Refer to your Android device documentation for more information.
Calibrating the hardware
The Measurement Computing Manufacturing Test department performs the initial factory calibration. Contact
Measurement Computing for details about how to return your device and have it calibrated to the factory
specifications.
Field calibration is not supported.

9
Chapter 3
Functional Details
Analog input acquisition modes
The USB-231-OEM can acquire analog input data in two different modes – software paced and hardware paced.
Software paced mode
You can acquire one analog sample at a time in software paced mode. You initiate the A/D conversion with a
software command. The analog value is converted to digital and returned to the computer. You can repeat this
procedure until you have the total number of samples that you want.
The maximum throughput sample rate in software paced mode is system-dependent.
Hardware paced mode
You can acquire data from up to eight channels in hardware paced mode. The analog data is continuously
acquired and converted to digital values until you stop the scan. Data is transferred in blocks of samples from
the device to the memory buffer on your computer. The block size varies depending on the sample rate.
The maximum continuous scan rate is an aggregate rate. The total acquisition rate for all channels cannot
exceed 50 kS/s. The following table lists the scan rate when scanning from one to eight channels.
Maximum continuous scan rate
# channels
scanned
Sample rate
(kS/s)
1
50
2
25
3
16.67
4
12.5
5 10
6
8.33
7
7.14
8
6.25
You can start a hardware paced continuous scan with either a software command or with an external hardware
trigger event.

USB-231-OEM User's Guide Functional Details
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Board components
Board components are shown in Figure 2.
1
Micro-USB connector
2
34-pin header connector (J2)
Figure 2. Board components
USB connector
The Micro-USB connector provides +5 V power and communication. No external power supply is required.
When using the USB connector to connect to the USB host, leave the D+ and D- signals and VBUS on the 34-
pin connector disconnected.
Header connector J2
The 34-pin header connector provides the connections listed in the following pinout tables.
Caution! To ensure the specified EMC performance, the length of any wire or cable connected to the header
connector must be no longer than 0.5 m (20 in.).
Differential mode pinout
Do not connect to connector pins labeled NC.
J2 differential pinout
Pin
Signal name
Pin description
Pin
Signal name
Pin description
1
AOUT0
Analog output 0
2
AOUT1
Analog output 1
3
AGND
Analog ground
4
AGND
Analog ground
5
CH3H
Analog input 3 HI
6
CH3L
Analog input 3 LO
7
CH2H
Analog input 2 HI
8
CH2L
Analog input 2 LO
9
CH1H
Analog input 1 HI
10
CH1L
Analog input 1 LO
11
CH0H
Analog input 0 HI
12
CH0L
Analog input 0 LO
13
AGND
Analog ground
14
AGND
Analog ground
15
D–
USB differential data signals
16
VBUS
USB power
17
D+
USB differential data signals
18
LED
Status LED driver
19 GND Digital ground 20 DIO0 DIO bit 0
21
DIO1
DIO bit 1
22
DIO2
DIO bit 2
23 DIO3 DIO bit 3 24 DIO4 DIO bit 4
25
DIO5
DIO bit 5
26
DIO6
DIO bit 6
27
DIO7
DIO bit 7
28
NC
No connection
29
TRIG
Digital trigger input
30
NC
No connection
31
NC
No connection
32
GND
Digital ground
33
CTR
Counter input
34
+VO
User voltage output

USB-231-OEM User's Guide Functional Details
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Single-ended mode pinout
Do not connect to connector pins labeled NC.
J2 single-ended pinout
Pin
Signal name
Pin description
Pin
Signal name
Pin description
1
AOUT0
Analog output 0
2
AOUT1
Analog output 1
3
AGND
Analog ground
4
AGND
Analog ground
5
CH3H
Analog input 3
6
CH3L
Analog input 7
7
CH2H
Analog input 2
8
CH2L
Analog input 6
9
CH1H
Analog input 1
10
CH1L
Analog input 5
11
CH0H
Analog input 0
12
CH0L
Analog input 4
13
AGND
Analog ground
14
AGND
Analog ground
15
D–
USB differential data signals
16
VBUS
USB power
17
D+
USB differential data signals
18
LED
Status LED driver
19
GND
Digital ground
20
DIO0
DIO bit 0
21
DIO1
DIO bit 1
22
DIO2
DIO bit 2
23
DIO3
DIO bit 3
24
DIO4
DIO bit 4
25
DIO5
DIO bit 5
26
DIO6
DIO bit 6
27
DIO7
DIO bit 7
28
NC
No connection
29
TRIG
Digital trigger input
30
NC
No connection
31
NC
No connection
32
GND
Digital ground
33
CTR
Counter input
34
+VO
User voltage output
Signal connections
Analog input
You can connect up to eight single-ended inputs or up to four differential inputs to connectors CH0H/CH0L
through CH3H/CH3L. The input voltage range is ±10 V. Figure 3 shows the USB-231-OEM analog input
circuitry.
Figure 3. USB-231-OEM analog input circuitry
The main analog input circuitry blocks are as follows:
MUX—The multiplexer (MUX) routes one AI channel at a time to the mode selector multiplexer
(DIFF/SE MUX).
DIFF/SE MUX—The mode selector MUX selects between DIFF mode and SE measurement mode.
IA— The instrumentation amplifier (IA) removes the common mode signal and buffers the analog input
signal before it is sampled by the analog-to-digital converter (ADC).
ADC—The ADC digitizes the AI signal by converting the analog voltage into digital code.

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AI FIFO—The DAQ device can perform both single and multiple analog-to-digital conversions of a fixed or
infinite number of samples. A first-in-first-out (FIFO) buffer holds data during AI acquisitions to ensure no
data is lost.
ADC Control—The ADC control circuitry sets the conversion rate of the ADC, sets the input
configuration, drives the scanning sequence, and starts acquisitions synchronous with the TRIG or CTR
signal
Single-ended configuration
When configured for SE input mode, the input signal is referenced to analog ground (AGND) and delivered
through two wires:
Connect the wire carrying the signal to be measured (CHxH or CHxL).
Connect the second wire to AGND.
The input range for single-ended mode is ±10 V. The single-ended mode pinout is shown in the Single-ended
mode pinout section on page 11.
Differential configuration
When configured for differential input mode, the input signal is measured with respect to the low input and
delivered through three wires:
Connect the wire carrying the signal to be measured to CHxH
Connect the wire carrying the reference signal to CHxL
Connect the third wire to AGND.
The differential mode pinout is shown in the Differential mode pinout section on page 10.
Note: To perform a single-ended measurement using differential channels, connect the signal to CHxH and
ground the associated CHxL input.
Input range
The USB-231-OEM has an input range of ±10 V. For DIFF mode, each AI should stay within ±10 V with
respect to AGND, and the voltage between positive and negative inputs should be lower or equal to ±10 V. For
SE mode, signals of ±10 V at any analog input connector with respect to AGND are accurately measured.
Beyond ±10 V, the input signal begins clipping as shown in Figure 4. Typically, this clipping begins at ±10.5 V.
Figure 4. Analog input exceeding ±10 V returning clipped results

USB-231-OEM User's Guide Functional Details
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Multichannel scanning
The USB-231-OEM can scan multiple channels at high rates and digitize the signals accurately. However, you
should consider several issues when designing your measurement system to ensure the high accuracy of your
measurements:
Use low impedance sources – To ensure fast settling times, your signal sources should have an
impedance of <1 kΩ. Large source impedances increase the settling time of the DAQ device and decrease
the accuracy at fast scanning rates.
Use short high-quality cabling – Using short high-quality cables can minimize several effects that
degrade accuracy including crosstalk, transmission line effects, and noise. The capacitance of the cable also
can increase the settling time.
To ensure the specified EMC performance, operate this product only with shielded cables and accessories.
The length of any wire or cable connected to the connector must be no longer than 0.5 m (20 in.).
Avoid scanning faster than necessary – Design your system to scan at slower speeds to give the DAQ
device more time to settle to a more accurate level when switching between channels.
Analog output
Figure 5 shows the USB-231-OEM analog output circuitry.
Figure 5. USB-231-OEM analog output circuitry
The main analog output circuitry blocks are as follows:
Protection – The protection circuit prevents damage of the buffers in case of a short circuit or an
overvoltage condition.
Buffer – The buffer amplifies the analog signal to the ±10 V range and ensures the driving capability for
the external load.
DAC 0 and DAC 1 – The digital-to-analog converters (DAC) convert the digital signals into low-level
analog signals.
AO FIFO – The AO FIFO (first-in-first out) ensures that data is transferred to the DACs in a timely manner
without being affected by USB latencies.
DAC Control – The DAC control sets the DAC data rate and the startup condition, which could be
triggered by the TRIG signal.
Analog output signals are referenced to AGND. Connect the loads between AOUT0 or AOUT1 and AGND as
shown in Figure 6 on page 14.

USB-231-OEM User's Guide Functional Details
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Figure 6. USB-231-OEM analog output connection diagram
Power-on state
The AO circuitry exhibits a short glitch when the device is powered on and when the DAQ device exits suspend
mode. After power-up, the AO circuitry is reset to 0 V.
AO range
The AO range is ± 10 V.
Minimizing glitches on the output signal
When using a DAC to generate a waveform, you may observe glitches on the output signal. These glitches are
normal; when a DAC switches from one voltage to another, it produces glitches due to released charges. The
largest glitches occur when the most significant bit of the DAC code changes. You can build a low-pass
deglitching filter to remove some of these glitches, depending on the frequency and nature of the output signal.
Generating analog output data
The USB-231-OEM can generate analog output data in two different modes – software paced and hardware
paced.
Software paced – Software controls the rate at which data is generated. Software sends a separate
command to the hardware to initiate each DAQ conversion. Software-paced generations are also referred to
as immediate or static operations. They are typically used for writing a single value out, such as a constant
DC voltage.
Hardware paced – A digital hardware signal controls the generation rate. This signal is generated
internally on your device. Hardware-paced generations have advantages over software-timed acquisitions,
such as the time between samples can be much shorter, and the timing between samples can be
deterministic (data is sampled at regular intervals).
Hardware-timed operations are buffered. During hardware-paced AO generation, data is moved from a PC
buffer to the onboard FIFO on the DAQ device using USB signal streams before it is written to the DACs one
sample at a time. Buffered generations allow for fast transfer rates because data is moved in large blocks rather
than one point at a time.
The sample mode can be either finite or continuous in a buffered I/O operation:
In finite sample mode, a specified number of samples are generated, and then the generation stops.
In continuous mode, an unspecified number of samples are generated until you stop the generation.

USB-231-OEM User's Guide Functional Details
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Digital I/O
You can connect up to eight digital I/O lines to DIO0 through DIO7. GND is the ground-reference signal for
digital I/O. Each digital I/O line is bit-configurable as input or output. Digital input voltage ranges from 0 V to
5 V are permitted, with thresholds of 0.8 V (low) and 2.3 V (high). Each DIO channel can sink up to 4 mA for
direct drive applications when used as an output. All digital I/O updates and samples are software-paced.
Figure 7 below shows DIO0 through DIO7connected to signals configured as digital inputs and digital outputs.
1
DIO0 configured as an open drain digital output driving a LED
2
DIO4 configured as a digital input receiving a TTL signal from a gated inverter
3
DIO7 configured as an digital input receiving a 0 V or 5 V signal from a switch
Figure 7. Example of connecting a load
Caution! Exceeding the maximum input voltage ratings or maximum output ratings – listed in the
Specifications chapter – can damage the device and the computer. Measurement Computing is not
liable for any damage resulting from such signal connections.
Power-on states
At system startup and reset, the USB-231-OEM sets all DIO lines to high-impedance inputs. The device does
not drive the signal high or low. Each line has a weak pull-down resistor connected to it.
DIO protection
To protect the DAQ device against overvoltage, undervoltage, and overcurrent conditions, as well as ESD
events, avoid these fault conditions by using the following guidelines:
If you configure a DIO line as an output, do not connect it to any external signal source, ground signal, or
power supply.
If you configure a DIO line as an output, understand the current requirements of the load connected to these
signals. Do not exceed the specified current output limits of the DAQ device. Measurement Computing has
several signal conditioning solutions for digital applications requiring high-current drive.
If you configure a DIO line as an input, do not drive the line with voltages outside of its normal operating
range. The DIO lines have a smaller operating range than the AI signals.
Treat the DAQ device as you would treat any static-sensitive device. Always properly ground yourself and
the equipment when handling the DAQ device or connecting to it.

USB-231-OEM User's Guide Functional Details
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Trigger input
The TRIG connector is an external digital trigger input. The trigger mode is software-selectable for rising edge-
or falling edge detection.
Counter input
The CTR connector is a 32-bit counter that can count rising edges. Edges can only be counted up from 0.
Counting down is not supported – you cannot set the initial count to 100 and count down to 99, 98, 97.
USB signals, power (D–, D+, VBUS)
When using a USB connector on your motherboard to connect the USB-231-OEM to the USB host through the
34-pin connector, do not connect to the USB connector.
Status LED driver (LED)
The LED signal indicates the device status as shown in the following table:
LED State Device Status
Off
Device is not connected or is in suspend mode.
On, not blinking
Device is connected and functioning normally.
Blinking Device has encountered an error.
An open collector output drives the LED signal. For applications that use the LED signal, connect an external
pull-up resistor from the LED signal to an external voltage.
LED electrical characteristics are listed in the Specifications chapter.
To drive a status LED, refer to the circuit in Figure 8.
Figure 8. Circuit to drive a status LED

USB-231-OEM User's Guide Functional Details
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To use the LED signal to monitor the device state, refer to the circuit in Figure 9.
Figure 9. Circuit to monitor device state with LED signal
+VO power source
Figure 10 shows the +VO power source circuitry of the USB-231-OEM.
Figure 10. +VO power source circuitry
The main blocks featured in the +VO power source circuitry are as follows:
+5 V Source—Regulated 5 V supply.
+5 V Protection—Circuit for overvoltage, over current, and short circuit protection.
The +5 V source is limited at 200 mA typically. In case of hard short circuit to ground, this limit is further
reduced to avoid excessive power dissipation.
Connecting the load
The return connector for the +5 V source is the GND connector. The +5 V load should be connected between
the +VO connector and GND. The current delivered by the USB-231-OEM at the +VO connector is sourced
from the USB connector. To meet the USB specifications, a maximum of 150 mA can be used from the +VO
connector.

USB-231-OEM User's Guide Functional Details
18
Figure 11. Connecting the +VO power source load
The + 5 V power is always enabled and the voltage is present at the +VO connector when the device is in active
mode. The +5 V power source is not available for about one second after the device is first connected to the
USB connector or when the device is in suspend mode.
Ground
The analog ground (AGND) connectors provide a common ground for all analog channels. The digital ground
(GND) connectors provide a common ground for the digital, counter, and power connector.
For more information about signal connections
For more information about analog and digital signal connections, refer to the Guide to DAQ Signal
Connections on our website at www.mccdaq.com/support/DAQ-Signal-Connections.aspx.

USB-231-OEM User's Guide Functional Details
19
Mechanical drawings
Figure 12. Circuit board dimensions

20
Chapter 4
Specifications
All specifications are subject to change without notice.
Typical for 25 °C unless otherwise specified.
Specifications in italic text are guaranteed by design.
Analog input
Table 1. Analog input specifications
Parameter Condition Specification
A/D converter type
Successive approximation
ADC resolution 16 bits
Sampling rate Maximum aggregate 50 kS/s
Number of channels 8 single-ended or 4 differential; software-selectable
Input voltage range ±10 V
Working voltage
±10 V
Overvoltage protection
Power on
±30 V max
Power off
±20 V max
Input impedance >1 GΩ
Input bias current ±200 pA, typ
INL
±1.8 LSB
DNL
16 bits no missing codes
CMRR 56 dB (DC to 5 kHz)
Input bandwidth
300 kHz
Trigger sources
Software, TRIG
Absolute accuracy (analog input DC voltage measurement accuracy)
Table 2. Absolute accuracy (no load)
Range At full scale (typical at 25 °C) At full scale (maximum over temperature) System noise
±10 V
6 mV
26 mV
0.4 mV
rms