USB-DIO48DO24 Digital I/O and FET Board

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  • High-speed USB 2.0 device, USB 3.0 and 1.1 compatible
  • 48 lines of digital I/O
  • 24 fully protected and isolated FET 2A outputs
  • High retention type B USB connector
  • Mini USB header connector in parallel with type B for stacking and embedded applications
  • Six (6) 8-bit ports independently selectable for inputs or outputs
  • All I/O lines buffered with 32 mA source, 64mA sink current capabilities
  • I/O Buffers can be enabled or tri-stated under program control
  • Jumper selectable I/O pulled up to 5V for contact monitoring, pulled down to ground or floating in 8-bit groups
  • Jumper selectable power provided via USB cable or external power supply for higher source current capabilities
  • Resettable fused +5VDC outputs per 50-pin connector
  • Standard 50-pin IDC-type shrouded connectors with key
  • Removable internal terminal board for ease of wiring
  • PC/104 module size and mounting compatibility (3.550″ by 3.775″)
  • Rugged, industrial, steel enclosure
  • Compatible with industry standard I/O racks like Grayhill, Opto 22, Western Reserve Controls, etc.
  • Labview VI driver
  • Now with Firmware 2.0 features!
    Onboard Watchdog Timer, configurable power-on defaults, digital input debouncing and latching, digital output Pulse Width Modulation (PWM) and Matrix Mapping
  • Designed, made, supported, and manufactured in the USA


  • 24 I/O, 12 FET output version
  • 24 FET output only version
  • OEM (board only) version for embeddeed applications
  • External power components and regulated AC/DC adapter
  • Extended operating temperature (-40° to +85°C)
  • Screw terminals for power input provide high retention connection
  • RoHS Compliant version. Please contact us for ordering information
  • Support for Wind River VxWorks (call for ordering information)
Last updated on February 21, 2024, 11:08 am


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48 Channel USB Digital Input/Output USB Module with 24 Solid State FET Relay Outputs

This USB board was designed to be used in today’s new Kiosk designs as a highly functional and compact I/O module. It is also an ideal solution for adding portable, easy-to-install digital I/O capabilities and solid state FET outputs to any computer with a USB port. It is a high-speed USB 2.0 device, USB 3.0 and 1.1 compatible. The unit is plug-and-play allowing quick connect/disconnect whenever you need additional I/O on your USB port.

The board features 48 or 24 channels of TTL-compatible digital I/O with high output current capabilities. Each digital port can be programmed to accept inputs or to drive outputs. Power is supplied to the card via the USB cable, or, for higher source current capabilities, an external power option may be ordered. All I/O lines are buffered by a type 74ABT543A tristate buffer transceiver capable of sourcing 32mA or sinking 64mA. Jumper selected resistors permit configuration of each 8-bit I/O group for pull-up (to +5 VDC), pull-down (to ground) or floating depending on the application requirement. Pull-ups are useful for contact monitoring, while pull-downs assure that there are no erroneous outputs at power-up until the card is initialized by system software.

The board also features 24 or 12 high side power MOSFET switch outputs. The fully protected outputs are de-energized at power-up to prevent an unintended control signal until turned on via software command. Each output shares a common switched voltage of 5-34VDC at up to 2A. Data to the solid state outputs are latched.

The I/O wiring connections for the 48 digital I/O lines are via two industry standard 50-pin connectors. One 50-pin connector is used for the 24 solid state FET outputs. For external circuits, fused +5VDC power is available at pin 49 of each I/O connector. The resettable fuse is rated to hold at 50mA continuous, and to trip at 150mA.

The USB-DIO48DO24 includes an internal, removable spring cage termination board (STB) to simplify wiring connections. The STB-DIO48DO24 plugs directly into the vertical IDC connectors of the USB-DIO48DO24 circuit board, inside the included enclosure. The USB-DIO48DO24 is designed to be used in rugged industrial environments but is small enough to fit nicely onto any desk or testing station. Extended temperature of (-40° to +85°C) is available. The board is PC/104 sized (3.55 x 3.775 inches, 90mm x 96mm) for added flexibility in embedded applications and ships inside a rugged powder-coated steel enclosure with anti-skid bottom.

The USB-DIO48DO24 utilizes a high-speed custom function driver optimized for a maximum data throughput that is thousands of times faster than the USB human interface device (HID) driver used by many competing products. This approach maximizes the full functionality of the hardware along with capitalizing the advantage of high-speed USB 2.0. The USB-DIO48DO24 is supported for use in most operating systems and includes a free Windows and Linux (including macOS) compatible software package. This package contains sample programs and source code in C#, Delphi, and Visual C++ for 32-bit and 64-bit Windows. Also provided is a graphical setup program in Windows. Linux support includes installation files and samples for programming from user level via an open source kernel driver. Third party support includes a Windows standard DLL interface usable from the most popular application programs, and includes LabVIEW VIs. Embedded OS support includes the family of Windows Operating Systems including IoT, please contact ACCS for compatibility with your specific OS.

Firmware 2.0 Features

Onboard Watchdog Timer. If your application fails to communicate with the device within a specified timeout period (up to hundreds of seconds) the onboard intelligence will change all the output ports and values to the configured “safe” state.

Need a DAC to power up at 1 Volt? Want the digital output port to generate a square wave as soon as the firmware is loaded? Now you can configure the power-on default states for all possible outputs.

Command the onboard intelligence to perform digital input debouncing and latching. Debouncing time constants from hundreds of microseconds to hundreds of milliseconds allows a wide variety of low-pass filtering options. Latching inputs record low- and high-going pulses that your application may otherwise have missed.

PWM allows programmable duty-cycle square wave output on any digital output. MAP is our new Matrix Mapping feature, wherein you can command the onboard intelligence to automagically copy the state of one bit onto another bit, with no computer interaction required.


The OEM (board only) version is perfect for a variety of embedded applications. What makes the OEM option unique is that its PCB size and pre-drilled mounting holes match the PC/104 form factor (without the bus connections). This ensures easy installation using standard standoffs inside most enclosures or systems. The board can be added to any PC/104-based stack by connecting it to a USB port usually included on-board with embedded CPU form factors. The USB-DIO48DO24 board can also be installed using standoffs inside other enclosures or systems. For embedded OEM type applications, an additional micro-fit USB input header is provided in parallel with the type B connector.


High Retention USB Connector

The ever-growing presence of USB in the industrial/military marketplace has driven the need for USB connections to be reliable, dependable, and unfailing. Gone are the days of loose USB connections. A type B USB connector is used on all ACCES USB/104 products which features a high retention design that complies with the class 1, Div II minimum withdrawal requirement of over 3 pounds of force (15 Newtons). This connector has an orange color-coded insulator to quickly differentiate it from standard USB connectors. Using these USB connectors increases reliability in your system and ensures a tight connection. For embedded OEM type applications, an additional miniature USB input header is provided in parallel with the type B connector.


  • Process Monitoring
  • Manufacturing/Production Test
  • Mobile Solutions
  • Test Equipment
  • Kiosks
  • Robotics
  • Machine Control
  • Monitoring and Control
  • Security Systems, Energy Management
  • Relay Monitoring and Control
  • Sensing Switch Closures or TTL, DTL, CMOS Logic
  • Driving Indicator Lights or Recorders
  • Industrial Automation
  • Embedded OEM


Available accessories include a DIN-Rail mounting adapter, model MP104-DIN. Also available is our low cost IIB-24 which will add optical isolation to any standard 24-channel digital input port on a 50 pin connector. To make use of the miniature embedded USB header connector, we offer a variety of embedded OEM USB cables. Additional accessories include flat ribbon cables and other DIN-rail mountable screw terminal boards for remote wiring and installation.

Need more isolation?

Isolate your I/O with our USB-ISOLATOR accessory! Tru-Iso™ signal isolation up to 4kV meets EN60601 standards in a rugged industrial-grade, extended temp (-40 to +85°C) package — no connection to power needed! Use with our 1-foot USB cable and avoid tangles. OEM-version available, featuring picoblade microfit headers for hassle-free embedded cabling.


Data Sheets



Drivers and Downloads

Full list of available Downloads: Software Packages, Drivers, Manuals, and other documents

Information about our Free Software packages:

ACCES is proud to provide a full suite of software support with every Data Acquisition product. We are committed to supporting the most popular operating systems and platforms for our customers. Currently we are actively supporting XP -> 10, both 32 & 64 bit, including “Server 2008,” “Embedded,” and “Compact” flavors for all plug-and-play products including PCI, PCI Express, USB, and more. Many products continue to ship with support for additional operating systems such as DOS, Windows 95, 98, Me, NT4, and 2000.


Among the software we deliver with our products are sample programs in a wide variety of programming languages. These samples are used to demonstrate the software interfaces to our products — and many can be used as-is in your production environments, or to test functionality of the devices out-of-the-box. We’re currently actively supporting sample programs in Microsoft Visual C#, Visual Basic, Delphi, and Visual C/C++, with many devices including samples in Borland C/C++ 3.1 for DOS. Additionally we provide National Instruments LabVIEW compatible DLLs and many demonstration VIs for our devices.


Drivers for various operating systems are also provided, including active support for Windows XP -> 10 — all in both 32-bit and 64-bit flavors, and including consumer, server, and embedded varieties — as well as the 2.6 and newer Linux kernels and recent OSX / macOS versions. Many products continue to ship with driver support for Windows 95, 98, Me, NT4, and Windows 2000, but support for these operating systems is considered deprecated.

Setup Programs and Utilites

Our Data Acquisition devices also include a graphical setup utility that walks you through the process of configuring any option jumpers or switches on the device, as well as explaining a little about the various connectors present.

Many devices also include utility programs – little tools to make your use of the device easier, such as EWriter, a program that allows you to read and write data in the user-accessible EEPROM locations on all our USB data acquisitition products; or WinRISC, a “Really Incredibly Simple Communications” terminal program that lets you get started instantly with serial devices.

“Register Level” Documentation

Besides all this software in all these languages and operating systems ACCES has a policy of open and transparent development: none of our lowest-level “register” interfaces are hidden from you — we document every register in every bus card, every command in every serial board, and every usb control transfer in every USB Data Acquisition board. These lowest-level interfaces allow you to develop for our products in ANY operating system or language, regardless of our actively supporting it or having a driver for it. We have customers actively developing in ADA, Android, Python, Java, MATLAB, Solaris, and more, just by referring to our complete low-level interface documentation! And we provide the full source code to all of our drivers, regardless of operating system, to give you an even bigger head start in your own development tasks.

No Fees or Royalties

All of this software is provided at no additional charge, and is licensed under any of a variety of flexible — and royalty free — options. Check out our software license explanation if you’d like more information.

USB and Performance

Our USB Data Acquisition products use our “AIOUSB” driver package in Windows and Linux. This driver package includes 32-bit and 64-bit support, and consists of low-level driver components and a high-level API library. This custom interface driver enables our USB devices to achieve 4000 transactions per second, compared to the competitions’ “HID” drivers that cap out around 50 transactions per second. You can read all about the API in the USB Software Reference Manual linked below, and included in every applicable Software Package. (The Linux version of the AIOUSB API is almost identical to the Windows API, and is documented in the aiousb.html file included in the Linux software package.) Like all of our software, full source code is always provided.

Custom Software

ACCES also offers Custom Software Services for our products. Our prices are unbelievably low, often as inexpensive as free! If you need something tweaked to support your needs, or an entire enterprise application developed from scratch, it is definitely worth your time to inquire with us, first.

Further information about available ACCES Software:

Redistributing Windows Drivers
A list of ACCES drivers and the files that compose them under different versions of Windows, so you can easily redistribute ACCES cards and drivers.


ACCES has successfully partnered with Wind River to bring our entire line of USB DAQ boards to VxWorks 7!

Our newly available driver and easy-to-use API-library, including full source and sample code, supports ReNumeration for loading firmware across the USB cable as well as our GenericVendorWrite and GenericVendorRead functions, compatible with our Windows AIOUSB.dll API. Additional AIOUSB API functions are being ported, ask for details!

With our aioUSB.VxWorks library USB DAQ can now be used with the utmost confidence for real-world/real-time/rugged applications. Using VxWorks 7 as the solid foundation, and positive-retention cables in either micro-fit or USB-B-with-screw, as well as rugged steel enclosures and DIN-Rail or PC/104-mounting options, USB is no longer “just for desktops”.

You can find more information about our VxWorks libraries and services on our Wind River Silver Partner page.

TTL Digital Input/Output Lines

  • Channels / Groups: 48 in 8-bit groups
  • Inputs:
    • Logic High: 2.0 VDC minimum, 5.5 VDC max.
    • Logic Low: -0.5 VDC min., +0.8 VDC max.
  • Outputs:
    • Logic High: 2.0 VDC minimum, source 32 mA
    • Logic Low: 0.55 VDC maximum, sink 64 mA

Isolated FET Outputs

  • Number: 24 Solid State FETs
  • Output Type: High Side Power MOSFET Switch. Protected against short circuit, over-temperature, ESD, and can drive inductive loads.
  • Voltage Range: (customer supplied) 5-34VDC recommended for continuous use, 40VDC absolute max.
  • Current Rating: 2A maximum
  • Turn-on time: 90uS (typical)
  • Turn-off time:110uS (typical)
  • Total VBB Current not to exceed 10A cumulative on all outputs

Bus Type

  • USB 2.0 high-speed


  • Operating Temp.: 0°C to 70°C
  • Storage Temp.: -40°C to +85°C
  • Humidity: 0%-90% RH, non-condensing
  • Board Dimension: 3.550 x 3.775 inches
  • Box Dimension: 4.00 x 4.00 x 1.4 inches


  • Basic Unit: 318mA typical (no load)
  • Auxiliary Outputs: +5VDC via 0.5A resettable fuse per 50 pin connector
  • Bus Powered: +5VDC provided via USB bus up to 500mA
  • Externally Powered: ** Optional on-board external power circuitry and AC/DC (regulated 5V output) adapter can be ordered (“-PR” option) if source current use is expected to be greater than what can be supplied by the USB bus (typically 500mA).

Regulatory Compliance

  • This product is designed to be in full compliance with CE requirements.
ModelDescriptionPrice (USD)

USB Module with 24 Solid State FET Relay Outputs


24 Channel USB Digital Input/Output USB Module with 12 Solid State FET Relay Outputs


48 Channel USB Digital Input/Output USB Module with 24 Solid State FET Relay Outputs

Direct Connect
STB-DIO48DO24 Direct connect 72-channel spring-cage terminal board for all 48 channels. Included with the module. If ordered separately: $72
Cable Connect
CAB50F-6 50 pin ribbon cable with female header connectors, 6 feet long $30
C104-50F-12 50-pin ribbon cable with female headers, 12″ long $15
STB-50 DIN-rail mountable screw terminal board for 50 pin header type connector $44
STB-48CH 48 Channel external screw terminal board for 26 to 12 AWG wire and remote wiring $149
IIB-24 24-channel optical isolator input board for each 50-pin header $149
ROB-24 24-channel electromechanical relay board for each 50-pin header $249
Hardware and Hub
MP104-DIN USB/104 DIN Rail Mount
USB-104-HUB Rugged, industrial grade, 4-port high-speed USB 2.0 hub
Model Options (call for pricing)
-PR +5VDC external power jack and regulated AC/DC adapter
-ST External power components & screw terminals for power input (high retention)
-T Extended operating temperature (-40°C to +85°C)
-OEM Board only (no enclosure)
-RoHS RoHS compliant version