Service USB core

Owners of other interfaces than Service USB core can neglect the following chapter.

Service USB core

Service USB core is used as the base for proprietary development. It is an open frame printed circuit with four digital inputs and four digital outputs. The I/O ports work with 5V logic and have no protection against overvoltage. The large assortment of additional software makes it possible to control the interface of nearly every program.


System requirements

A Macintosh with USB and OSX 10.5 to 10.8 is required to operate Service USB plus. Up to 100 Service USBs can be run on a Macintosh.


Scope of delivery

  • Service USB core (printed circuit board)
  • USB A/B cable
  • CD-ROM with driver and a lot of sample programs
  • OSX-Examples for Runtime Revolution, RealBasic, Apple-Script, FileMaker, RagTime, Xcode (C, C++, Objective-C, Cocoa, Java, AppleScriptStudio), 4th Dimension, MaxMSP, Adobe Director, BlueJ, Scratch, TCP/IP, Numbers and the UNIX-Shell

Furthermore you will find Quicktime-Films about fischertechnik®-models, and a detailed instruction manual.


Hardware description

This is Service USB core top view including all connectors and control lamps:

Service USB core

Service USB core top view


Service USB core has the following connections and interfaces:


  • An USB connector at the back in the centre. Power is supplied to Service USB core via the USB interface.
  • Four red LEDs for the status indication of each input.
  • Four red LEDs for the status indication of each output.
  • One green LED shows that the Macintosh driver has been connected and that the interface is working properly. This LED must always be on during use.
  • One 74HCT244 mounted on a holder, which works as a buffer between the microcontroller and the I/O lines
  • One strip connector with 2.54mm (0.1") clearance connects to the 4 inputs, 4 outputs and 5V auxiliary voltage.
  • One resettable fuse between USB and buffer-IC. The green LED indicates that there is no short.
  • Four distance pieces with metric screw thread M3 for mounting the board in self made apparatus.


Dimensions and connectors

Service USB core

Service USB core top view dimensions and pinout


5V - Auxiliary output voltage. This is 5V from USB, fused with 100mA self resetting fuse.

O3-O0 - Digital outputs bit 3 to bit 0 with 5V logic level. Each output can draw a current of 6mA maximum.

I3-I0 - Digital inputs bit 3 to bit 0. The input current is less than 1µA. Unconnected inputs can switch by receiving static voltage through the air or by a wet finger. It is suggested to connect unused inputs to 0V (GND)

0V - All voltage instructions refer to this connection. It is the 0 volt reference point for all inputs and outputs. It is also known as ground (GND).

Warning: Under no circumstances a voltage more than 5V or a negative voltage is to be connected on any I/O.


Connection with ribbon cable

Commercially available flat ribbon cables with 2.54mm (0.1") female header can be used to connect Service and other printed circuit boards.

Service USB core

Service USB core with flat ribbon cable connection

Because the Service USB I/O lines are logic lines with 5V, the cable should be as short as possible to minimise external parasitic induction. The cable should be not longer than 20cm.



This connector complies to USB full speed with data transfer rate of 12Mb/s. The maximal power consumption is 100mA. The 5V from USB is the power supply for the Service USB core as well as the auxiliary voltage at the multi pin connector, which is protected with a resettable fuse.


The light emitting diodes

In each case four red LEDs indicate the state of the inputs and the outputs. Because of the high resistance of digital inputs the inputs can switch to a random state if they are not connected. In this case the input LEDs may have a random state or are flickering.
The green 5V LED shows that the Macintosh driver has been connected, that there is no shortage on the auxiliary voltage and that the interface is working properly. This LED must always be on during use.


Technical information

  • Dimensions: 50mm x 60mm x 18mm (width x depth x height)
  • Installation height: 25mm when connecting with flat ribbon cable.
  • Weight: 24g
  • Data transfer: USB full speed (12Mb/s)
  • USB current consumption: 100mA
  • Digital inputs: 4
  • Input level logical 0: 0 - 0.8V
  • Input level logical 1: 2 - 5V
  • Digital outputs: 4
  • Output level logical 0: 0 - 0.3V
  • Output level logical 1: 3.9 - 5V
  • Maximum output current: 6mA (for each output)
  • Status indication: 9 LEDs
  • Connector: Ten pin terminal strip (IDE double row header) with 2.54mm (0.1") grid spacing and 0.64mm (0.025") square pin.
  • Maximum data rate: 2000 Values per second.
  • Case protection category: IP00


Schematic diagrams

Service USB core

Block diagram of Service USB core

Service USB core

Circuit diagram of Service USB core