USB-DIO24H/37
24-Channel Digital I/O USB Device

User's Guide

May 2019. Rev 4© Measurement Computing Corporation

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HM USB-DIO24H_37.docx

Table of Contents
Preface

About this User's Guide ....................................................................................................................... 4
What you will learn from this user's guide ......................................................................................................... 4
Conventions in this user's guide ......................................................................................................................... 4
Where to find more information ......................................................................................................................... 4
Chapter 1

Introducing the USB-DIO24H/37 .......................................................................................................... 5
Overview: USB-DIO24H/37 features ................................................................................................................. 5
Functional block diagram ................................................................................................................................... 5
Chapter 2

Installing the USB-DIO24H/37 .............................................................................................................. 6
Unpacking........................................................................................................................................................... 6
Installing the software ........................................................................................................................................ 6
Installing the hardware ....................................................................................................................................... 6
Connecting the board for I/O operations ............................................................................................................ 6
Connectors and cables....................................................................................................................................................... 6
Field wiring, signal termination and conditioning ............................................................................................................ 7

Chapter 3

Functional Details ................................................................................................................................. 8
Components ........................................................................................................................................................ 8
37-pin I/O connector ......................................................................................................................................................... 8
USB connector .................................................................................................................................................................. 9
LED .................................................................................................................................................................................. 9
Pull-up resistors ................................................................................................................................................................ 9Power consumption ............................................................................................................................................ 9
Output (source) current limits ..........................................................................................................................................10
Output (sink) current limits ..............................................................................................................................................10

Mechanical Drawings ....................................................................................................................................... 10
Chapter 4

Specifications ...................................................................................................................................... 11
Digital input/output........................................................................................................................................... 11Counter ............................................................................................................................................................. 12
Data transfer rates ............................................................................................................................................. 12Power ................................................................................................................................................................ 12
General ............................................................................................................................................................. 13
Environmental .................................................................................................................................................. 13
Mechanical ....................................................................................................................................................... 13
Main connector and pinout ............................................................................................................................... 13
Declaration of Conformity .................................................................................................................. 15

3

Preface

About this User's Guide
What you will learn from this user's guideThis user's guide explains how to install, configure and use the USB-DIO24H/37 digital I/O board. This user's
guide also refers you to related documents available on our web site and to technical support resources.

Conventions in this user's guide
For more information
Text presented in a box signifies additional information and helpful hints related to the subject matter you arereading.
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 the 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-201 hardware is available on our website at www.mccdaq.com. You canalso contact Measurement Computing Corporation with specific questions.


Knowledgebase: kb.mccdaq.com
Tech support form: www.mccdaq.com/support/support_form.aspx
Email: techsupport@mccdaq.com
Phone: 508-946-5100 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.

4Chapter 1

Introducing the USB-DIO24H/37
Overview: USB-DIO24H/37 features
This manual explains how to install, configure and use the USB-DIO24H/37 digital I/O board. You can use thisboard in a variety of digital applications to control logic devices such as switches, gauges, relays, pumps, andsensors.
The USB-DIO24H/37 is a USB 2.0 low-speed device supported under popular Microsoft® Windows® operating
systems. It is designed for USB 1.1 ports and was tested for full compatibility with both USB 1.1 and USB 2.0
ports.
The USB-DIO24H/37 is a high drive, 24-line digital I/O device that includes one 32-bit external event counter.
Power is supplied by the +5 volt USB supply from your computer. No external power is required.
Digital I/O lines are accessed through a 37-pin connector. Each digital port can be configured for either input or
output. Digital channels are pulled up to +5V with 47k resistors.
The control register that sets the direction of the I/O ports is an emulation of the 82C55 in mode 0 (only). The
74FCT244 outputs are high-drive TTL, capable of sourcing 15 mA and sinking 64 mA.
The USB-DIO24H/37 board is completely plug-and-play, with no jumpers or switches to set. All board
addresses are set by your system's plug-and-play software.

Functional block diagram
USB-DIO24H/37 functions are illustrated in the block diagram shown here.

Figure 1. USB-DIO24H/37 functional block diagram

5Chapter 2

Installing the USB-DIO24H/37
UnpackingAs with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the device 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.
Contact us immediately if any components are missing or damaged.

Installing the software
Refer to the MCC DAQ Quick Start and the USB-DIO24H/37 product page on our website for information
about the software supported by the USB-DIO24H/37.
Install the software before you install your device
The driver needed to run the USB-DIO24H/37 is installed with the software. Therefore, you need to install thesoftware package you plan to use before you install the hardware.

Installing the hardware
To connect the USB-DIO24H/37 to the system, connect the USB cable to an available USB port on thecomputer or to an external USB hub connected to the computer.
When you connect the USB-DIO24H/37 for the first time, multiple Found New Hardware popup balloons open
when the operating system detects the device. When installation is complete, the USB LED should flash andthen remain on. This indicates that communication is established between the USB-DIO24H/37 and yourcomputer.
If the USB LED turns off
If the USB LED is on but then turns off, the computer has lost communication with the USB-DIO24H/37. To
restore communication, disconnect the USB cable from the computer, and then reconnect it. This should restore
communication, and the USB LED should turn back on.
Caution! Do not disconnect any device from the USB bus while the computer is communicating with the
USB-DIO24H/37, or you may lose data and/or your ability to communicate with the
USB-DIO24H/37.

Connecting the board for I/O operations
Connectors and cables
The table below lists the board I/O connector type and compatible cables for use with the USB-DIO24H/37.
Board connectors, cables, and accessory equipment
Connector typeCompatible cables

37-pin D-type connector
C37FF-x unshielded ribbon cable. x = length in feet6USB-DIO24H/37 User's Guide

Installing the USB-DIO24H/37

Figure 2. I/O connector pinout

Information on signal connections
General information regarding signal connection and configuration is available in the Guide to DAQ Signal
Connections (available for download from www.mccdaq.com/support/DAQ-Signal-Connections.aspx.)

The red stripe
identifies pin # 1

1

1

20

20

37

19

19

37

Figure 3. C37FF-x cable

Field wiring, signal termination and conditioning
Refer to the product page at www.mccdaq.com/usb-data-acquisition/USB-DIO24-Series.aspx for compatible
products to use with the USB-DIO24H/37.

7

Chapter 3

Functional Details
Components
The USB-DIO24H/37 has the following external components, as shown in Figure 5.


37-pin I/O connector
USB connector
LED

Figure 4. USB-DIO24H/37 components

37-pin I/O connector
The 37-pin connector provides 24 digital I/O, one counter, six ground, and two power connections.
The digital I/O port is configured as two 8-bit and two 4-bit ports based on an 82C55 mode 0 emulation. You
can configure each port independently for input (default) or output.
The CTR signal is the input to the 32-bit external event counter. The internal counter increments when the TTL
levels transition from low to high. The counter can count frequencies of up to 1 MHz.
The six ground (GND) pins are identical and provide a common ground for all USB-DIO24H/37 functions.
The two power pins (+5V) draw power from the USB connector. Each pin is a +5 volt output that is supplied by
the computer.
8

USB-DIO24H/37 User's Guide

Functional Details

Caution! The +5 V pins are outputs. Do not connect to an external power supply or you may damage theUSB-DIO24H/37 and possibly the computer
When configured for input, you can use the USB-DIO24H/37 digital I/O terminals to detect the state of any
TTL level input. Refer to the schematic shown in Figure 3-2. If you set the switch to the +5 V input, Port A0
reads TRUE (1). If you move the switch to GND, Port A0 reads FALSE.

Figure 5. Schematic showing switch detection by digital channel Port A0

Information on signal connections
General information regarding signal connection and configuration is available in the Guide to DAQ Signal
Connections (available for download from www.mccdaq.com/support/DAQ-Signal-Connections.aspx.)

USB connector
The USB connector provides +5 V power and communication. The voltage supplied through the USB connector
is system-dependent, and may be less than 5 V. No external power supply is required.

LED
The LED indicates the communication status of the USB-DIO24H/37. It uses up to 5 mA of current and cannot
be disabled. The table below explains the function of the USB-DIO24H/37 LED.
LED Illumination
LED status

Description

Steady green
Blinks continuously
Blinks three times

The USB-DIO24H/37 is connected to a computer or external USB hub.
Data is being transferred.
Initial communication is established between the USB-DIO24H/37 and the computer.

Pull-up resistors
Each digital port has an internal 47k pull-up resistor network. All digital pins are pulled up to +5 V (high logic
level) on power up and reset.

Power consumption
The maximum total output current that can be drawn from all USB-DIO24H/37 connections (power and digital
outputs) is 500 mA. This maximum applies to most personal computers and self-powered USB hubs.
Bus-powered hubs and notebook computers may limit the maximum available output current to 100 mA. To
overcome this limitation, an external self-powered hub can be used to supply the proper current level required
for full output capability.
Once you start running applications with the USB-DIO24H/37, each DIO bit can draw up to 15 mA. The
maximum amount of +5 V current available for external use, over and above that required by the USBDIO24H/37, is the difference between the total current requirement of the USB-DIO24H/37 (based on theapplication), and the allowed current draw of the computer platform 500 mA for desktop PCs and self-poweredhubs.
9

USB-DIO24H/37 User's Guide

Functional Details

The following power limits depend on whether you are sourcing current out of the USB-DIO24H/37, or you aresinking current into the USB-DIO24H/37.

Output (source) current limits
The maximum allowed current draw for a typical desktop computer and self-powered hub is 500 mA. You mustaccount for the supply current drawn from the USB supply for the USB-DIO24H/37 itself, plus the current usedby each DIO line. Since each DIO line can output 15 mA maximum, 24 DIO × 15 mA = 360 mA (maximum
rating for the chips).

Output (sink) current limits
Each USB-DIO24H/37 DIO output can sink up to 64 mA. For an individual line, this is not a problem. But if
you were to apply this maximum load to all 24 DIO lines, you would damage the USB-DIO24H/37 because thetotal amount of current is well over the maximum for the USB supply.
If you want to sink the maximum of 64 mA per DIO line, you can only do so with up to six lines. To sinkcurrent with all 24 DIO outputs at any one time, you can sink a maximum of 18 mA per line.

Mechanical Drawings

Figure 6. Circuit board dimensions

10

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.

Digital input/output
Table 1. Digital I/O specifications
Parameter

Specification

Digital input type
Digital output type
Number of I/O
Configuration

74ACT373
74FCT244
24 (Port A Bit 0 through Port C Bit 7)
2 banks of 8 and 2 banks of 4, or 3 banks of 8

Pull up/pull-down configuration

Internal 47 kΩ resistors configured for pull-up to +5 V

Input high voltage
Input low voltage
Output high voltage (IOH = –15 mA)
Output low voltage (IOL=64 mA)
Source current (Note 1): self -powered hub or
externally-powered root port hub
Source current (Note 2): bus-powered hub orbattery-powered root port hub
Sink current (Note 3)

2.0 V min, 5.5 V absolute max
0.8 V max, –0.5 V absolute min
2.4 V min
0.55 V max
Maximum = 15 mA per output

Power up/reset state

Not supported
Current sink max: 365 mA / (number of outputs)
64 mA max sink current for any single output
Input mode (high impedance)

Note 1:"Self-powered hub" refers to a USB hub with an external power supply. Self-powered hubs allow a connected
USB device to draw up to 500 mA. "Root port hubs" reside in the PC’s USB Host Controller. The USB port(s)on your PC are root port hubs. All externally powered root port hubs such as a desktop PC provide up to
500 mA of current for a USB device. In this configuration, all 24 digital outputs of the USB-DIO24H/37 cansource their per-pin maximum of 15 mA. This provides a total requirement of 15 mA*24 = 360 mA. Combining
this with the USB-DIO24H/37 operating current of 135 mA a fully-loaded current draw of 495 mA is realized.

Note 2:"Bus-powered hub" refers to a USB hub that derives power directly from the USB +5 V and does not have its
own power supply. These hubs allow a connected USB device to draw up to 100 mA. Battery-powered root port
hubs provide 100 mA or 500 mA, depending upon the manufacturer. A laptop PC that is not connected to an
external power adapter is an example of a battery-powered root port hub. If your laptop is constrained to the
100 mA maximum, the USB-DIO24H/37 is not guaranteed to work. In order to use the product you will need topurchase a self-powered hub.

Note 3:A low-side resettable fuse protects the USB-DIO24H/37. This is designed to protect the host PC or hub from anover current condition. Assuming all return currents in sinking applications return via the USB cable groundsignal, the maximum allowable return current is 500 mA. Include the USB-DIO24H/37 unloaded operating
current (135 mA) in your power budget.

11

USB-DIO24H/37 User's Guide

Specifications

CounterTable 2. Counter specifications
Parameter

Specification

Pin name (Note 4)
Counter type
Number of channels
Input source
Input type
Resolution
Schmidt trigger hysteresis
Input leakage current
Maximum input frequency
High pulse width
Low pulse width
Input low voltage
Input high voltage

CTR
Event counter1
CTR screw terminal
TTL, rising edge triggered
32 bits
20 mV to 100 mV
±1 µA
1 MHz
500 ns min
500 ns min
0 V min, 1.0 V max
4.0 V min, 15.0 V max

Note 4:CTR is a Schmitt trigger input.

Data transfer rates
Table 3. Data transfer rate specifications
Parameter

Specification

Digital I/O transfer rates (software paced)
Digital input
62 port reads or single bit reads per second typ
Digital output
125port writes or single bit writes per second typCounter/timer read/write rates (software paced)Counter read
62 port reads per second typCounter clear
125 port writes per second typ

Power
Table 4. Power specifications
Parameter

Conditions

Specification

Supply current (Note 5)
Input power requirements (Note 6)
USB +5V power available
USB +5V power output current (Note 7)

No load

100 mA typ, 135 mA max
4.75 V min, 5.25 V max
4.4 V min, 5.25 V max(350 mA) – (total output source
current)

USB +5V over-current protection

Measured at +5 screw terminals
Connected to: Self-powered hub
 Externally-powered root port hub
Resettable fuse

Hold current: 350 mA typ
Trip current: 700 mA typ
Trip/recovery time: 100 mS, max
On resistance: 1.3 Ω max

Note 5:This is the total (no load) current requirement for the USB-DIO24H/37.

Note 6:Bus-powered hubs can provide downstream USB power as low as 4.4 V. Although the USB-DIO24H/37 will
typically function at this 4.4 V minimum, guaranteed performance requires a minimum power supply voltage of
4.75 V. All self-powered and root port hubs will meet this 4.75 V minimum.

Note 7:

Refer to the available source/sink current level listed in the "Digital input/output" section.

12

USB-DIO24H/37 User's Guide

Specifications

GeneralTable 5. General specifications
Parameter

Conditions

Specification

USB controller clock error

25 °C
0 to 70 °C±30 ppm max±50 ppm max
USB 1.1 low-speed
USB 1.1, USB 2.0

Device type
Device compatibility

Environmental
Table 6. Environmental specifications
Parameter

Specification

Operating temperature range
Storage temperature range
Humidity

0 to 70 °C–40 to 85 °C
0 to 90% non-condensing

Mechanical
Table 7. Mechanical specifications
Parameter

Specification

Dimensions (L × W × H)
USB cable length
USB cable type

119 mm × 84 mm × 14 mm (4.69 × 3.31 × 0.55 in.)3 m (9.84 ft) max
A-B cable, UL type AWM 2527 or equivalent. (min 24 AWG VBUS/GND,
min 28 AWG D+/D-)

Main connector and pinout
Table 8. Connector specifications
Parameter

Specification

Connector typeCompatible cables

37-pin D-type
C37FF-x unshielded ribbon cable. x = length in feet.

13USB-DIO24H/37 User's Guide

Specifications

Table 9. Connector pinout
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

Signal name
CTR
NC
Port B Bit 7
Port B Bit 6
Port B Bit 5
Port B Bit 4
Port B Bit 3
Port B Bit 2
Port B Bit 1
Port B Bit 0
GND
NC
GND
NC
GND
NC
GND
+5
GND

Pin
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37

Signal name
+5
GND
Port C Bit 7
Port C Bit 6
Port C Bit 5
Port C Bit 4
Port C Bit 3
Port C Bit 2
Port C Bit 1
Port C Bit 0
Port A Bit 7
Port A Bit 6
Port A Bit 5
Port A Bit 4
Port A Bit 3
Port A Bit 2
Port A Bit 1
Port A Bit 0

14

Declaration of Conformity
Manufacturer:
Address:

Category:

Measurement Computing Corporation
10 Commerce Way
Norton, MA 02766
USAElectrical equipment for measurement, control and laboratory use.

Measurement Computing Corporation declares under sole responsibility that the productUSB-DIO24H/37
to which this declaration relates is in conformity with the relevant provisions of the following standards or otherdocuments:
EU EMC Directive 89/336/EEC: Electromagnetic Compatibility, EN 61326 (1997) Amendment 1 (1998)
Emissions: Group 1, Class A
EN 55011 (1990)/CISPR 11: Radiated and Conducted emissions.

Immunity: EN61326, Annex AIEC 61000-4-2 (1995): Electrostatic Discharge immunity, Criteria C.
IEC 61000-4-3 (1995): Radiated Electromagnetic Field immunity Criteria A.
IEC 61000-4-8 (1994): Power Frequency Magnetic Field immunity Criteria A.

Declaration of Conformity based on tests conducted by Chomerics Test Services, Woburn, MA 01801, USA in
February, 2006. Test records are outlined in Chomerics Test Report #EMI4445.06.
We hereby declare that the equipment specified conforms to the above Directives and Standards.

Carl Haapaoja, Director of Quality Assurance

Measurement Computing Corporation
10 Commerce Way
Norton, Massachusetts 02766(508) 946-5100
Fax: (508) 946-9500
E-mail: info@mccdaq.com
www.mccdaq.com

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