• High-speed USB 2.0 device, USB 3.0 and 1.1 compatible
  • 48 lines of digital I/O
  • 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
  • Drivers and sample application provided
  • Jumper selectable I/O pulled up to 5V for contact monitoring, pulled down to ground or floating
  • 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
  • PC/104 size (3.550 by 3.775 in.)
  • Rugged industrial 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


  • Board only version with no enclosure
  • External power components and regulated AC/DC adapter
  • Extended operating temperature (-40° to +85°C)
  • DIN rail mounting provision
  • Screw terminals for power input provide high retention connection
  • RoHS Available. Please contact us for ordering information
  • Support for Wind River VxWorks (call for ordering information)


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48 Channel Digital Input/Output USB Module

The USB-DIO-48 is an ideal solution for adding portable, easy-to-install digital I/O capabilities to any computer with a USB port. It is a high-speed USB 2.0 device, USB 3.0 and 1.1 compatible. The board is plug-and-play allowing quick connect/disconnect whenever you need additional I/O on your USB port.

This USB-DIO-48 features 48 bits of TTL-compatible digital I/O with high-current capabilities. Each digital port can be programmed to accept inputs or to drive outputs in six 8-bit ports. Power is supplied to the card via the USB cable, or for higher source current capabilities, an external power option may be ordered. The I/O wiring connections are via two industry standard 50-pin connectors. For external circuits, fused +5VDC power is available at pin 49 of each I/O connector. The resettable fuse is rated at 0.5A.

All I/O lines are buffered by a type 74ABT543A tristate buffer transceiver capable of sourcing 32 mA or sinking 64 mA. The buffers are configured under program control for input or output. Jumper selected resistors permit configuration of each 24-bit / 50-pin connector 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 and assure that there are no erroneous outputs at power-up until the card is initialized by system software.

The USB-DIO-48 is designed to be used in rugged industrial environments, with extended temperature available. The board is PC/104 sized (3.550 x 3.775 inches, 90mm x 96mm) for added flexibility in embedded applications and is small enough to fit nicely onto any desk or testing station.

Unlike most USB digital I/O products which primarily use a human interface device (HID) driver, ACCES providesw an easy to use, Windows/Linux-based, custom function driver capable of updating all 48-bits approximately 4000 times per second.

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, PCI-104, or PCI/104-Express stack by connecting it to a USB port usually included on-board with embedded CPU form factors such as EBX, EPIC, and PC/104. This is especially important since many newer CPU chipsets do not support ISA and have plenty of USB ports. Future stacks will be using the extremely fast PCI Express bus which is essentially overkill for simple monitoring and control. The USB-DIO-48 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 micro-fit USB input header is provided.


  • Mobile Solutions
  • Test Equipment
  • Kiosks
  • Robotics
  • Machine Control
  • Laboratory 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


The primary accessory is a direct connect 62-pin spring-cage terminal board (STB-DIO-48). Additional accessories include flat ribbon cables and DIN-rail mountable screw terminal boards for remote wiring and installation. Also available is our low cost IIB-24 which will add optical isolation to any standard 24-channel digital I/O 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.

ModelDescriptionPrice (USD)
USB-DIO-4848 Channel Digital Input/Output USB Module The USB-DIO-48 is an ideal solution for adding portable, …$195.00
STB-DIO-48Direct connect 62-pin spring-cage terminal board $49
STB-48CHExternal screw terminal board for 26 to 12 AWG wire and remote wiring $149
IIB-2424-channel optical isolator board for each 50-pin header $149
ROB-2424-channel electromechanical relay board for each 50-pin header $249
A24A24-channel mounting card for solid state I/O modules, 50-pin edge connector $149
CAB50F-650 pin ribbon cable with female header connectors, 6 feet long $30
CAB50-6Ribbon cable with 50-pin female edge connector on one end and 50-pin female connector on the other end $30
C104-50F-1250-pin ribbon cable with female headers, 12″ long $15
STB-50DIN-rail mountable screw terminal board for 50 pin header type connector $44
MP104-DINDIN rail mounting provision $19
USB-104-HUBRugged, 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
-STExternal power components & screw terminals for power input (high retention)
-TExtended operating temperature (-40°C to +85°C)
-OEMBoard only (no enclosure)
-RoHSRoHS compliant version