Service USB plus

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

Service USB plus


Service USB plus is the professional version of his "small brother" Service USB classic and is best used in laboratories, on fairs and for industrial purposes. It has an integrated wide range power supply and can be used all over the world on every power outlet. The digital outputs can directly drive lamps, relays and motors up to 15 watt. The pulse width modulated outputs allow different motor speed and brightness of lights.

The inputs can retrieve the status from switches and push buttons as well as the analog value from sensors in the range of 0-4.095V. The scope of delivery includes a lot of software, so that you can use the Interface of nearly every Macintosh-programme..


System requirements

A Macintosh with USB and OSX 10.5 to 10.8 is required to operate Service USB plus. For using the 12V/1.3A power outputs, the interface must be connected to a 115V or 230V power outlet. More than 100 Service USB plus can be controlled by one Macintosh.


Scope of delivery

  • Service USB plus (the interface)
  • USB A/B cable
  • plug power cord (available with EU, GB and US connector)
  • 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-movies about all supported fischertechnik®-models and a detailed instruction manual.


Hardware description

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

Service USB plus


Here is the detailed description of all connectors and lamps.

  • One USB connector on the right. Most functions are powered by this. Only the outputs are powered by the built in power supply, because the USB does not deliver enough power for this function.
  • One green LED „USB". It must glow all the time, if the Macintosh- Driver can correspond to the Service USB plus - this LED will show the correct function.
  • One green LED „12V" is connected to the internal 12V power supply. The power supply is only used for the digital outputs. If this LED is switched on, the outputs can be used.
  • Two red light bars with four LEDs each show the value of the analog inputs.
  • Sixteen red LEDs show the status of the digital inputs and outputs.
  • 21 cable clamps are mounted to the top for a fast connection of single wires and cords. All eight digital inputs, eight digital outputs and two analog inputs are connected to these clamps as well as GND, 5V and 12V.
  • One Sub D25 male connector on the upper left is connected with the same signals as the cable clamps.
  • One SUB D9 male connector on the lower left is the RS232 gateway. The RS232 can send and receive up to 19200 Baud. It is not possible to control the interface via RS232.
  • The RS232 is controlled by the Macintosh and is used for connecting serial devices. In addition a 5V auxiliary voltage and some inputs and outputs are led through.



Service USB plus


Function of the sockets

Service USB plus

Service USB Plus connectors and control lamps


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).

5V - There are 5V here which are used for the digital- and analog inputs. These 5V outputs together create a total maximum current of 100mA. A built-in fuse which resets itself automatically ensures that this current is not exceeded.

12V - There are 12V here, coming from the internal power supply. The maximum current is 1.3 A. This supply clamp is short circuit protected. Optionally there is a 24V version of Service USB plus available which has the same output power.

EX,EY - These are the analog inputs. The resolution is 12 bit. The input voltage range is 0V to 4.095V and the input resistance is 4.7kΩ. Resistors in the range of 0-200kΩ and currents up to 1mA can be measured using a direct connection. Sample schematics can be found in chapter 5.2. The inputs are protected against overload and underload up to ± 24V. These inputs can also be used as digital inputs, where EX = bit9 and EY = bit11.

In7-0 - These are the digital inputs. An input connected to 0V or an open input means logical 0. An input connected to 5V or 12V means logical 1. The keys and switches are usually connected between one of the inputs and the 5V clamp. In0 is the lowest bit; In7 is the highest bit. Eight LEDs indicate the state of the inputs. The inputs are protected against overload and underload up to ± 24V. The inputs In4-In0 can also be used as analog inputs.

Out7-0 - These are the digital outputs. The outputs switch directly to 12V or 0V. Analog output values are generated by turning on the pulse width modulation, which are generated by the interface itself in the range of 500Hz to 15.6Hz and up to 128 steps. The maximum output current is 1.3A. The current is either coming out of the pin or is flowing into the pin. The outputs are protected against short circuit and are also temperature protected. The output power is coming from the internal 12V switching power supply. The correct function of the internal power supply is shown by one green LED „12V". This LED must be switched on, if the internal power supply is connected to the 115/230V power outlet and if there is no short circuit.

RX - This is the RS232 receiving data input in the range of 300-19200 baud. The RX input can also be used as digital input bit 12. An open pin or a voltage greater than +3V means logical 0 and an input voltage below -3V means logical 1. The maximum input voltage at this connector must not exceed ±24V.

TX - This is the RS232 data output in the range of 300-19200 baud. This connector has a voltage level of -9V for signal mark and +9V for signal space.

HSKo - This output indicates whether Service USB plus is ready to receive characters. ( Service USB not ready: -9V; Service USB ready: +9V.) This output can also be used as digital output bit 10. In this case a logical 1 corresponds -9V and a logical 0 corresponds to +9V

HSKi - This input indicates whether the receiver is ready to receive characters. ( Receiver not ready: -3V to -18V; Receiver ready: +3V to +18V. ) A disconnected input means that the receiver is not ready. If the receiver does not have a handshake line, or it is unknown whether the line is connected, this line should be connected to the handshake output. A bridge between pins 6+7 (HSKi+HSKo) means that the serial data are always sent. This input can also be used as digital input bit 8. In this case a voltage greater than -3V or an open input corresponds to logical 0 and a voltage less that -3V corresponds to logical 1.

Out8-9 - These are digital outputs with 0V/5V logic level. These outputs are short circuit proof and resistant against external voltage up to ±24V. They can support a current of 1mA an can be connected directly to TTL and CMOS logic or the base of a bipolar transistor without an additional resistor. In this case the internal 2kΩ resistor works as base series resistor.

GND - All voltage instructions refer to this connection. It is connected to 0V.

In10 - This digital input bit 10 has the same input data than input bits In7-In0. It is protected against over- and undervoltage up to ±24V. This input can also be used as analog input.


Usage of the cable clamp

The clamp can hold wires and cords between 0,08 and 2,5 mm2. Wires greater than 0.7 mm2 can be inserted directly, while you need to pull down the orange fitting with your finger nail or a screw driver to insert smaller wires or strands. The orange fitting must also be pressed down completely to loose the cable or strand.

Service USB plus

A row of cable clamps


Sub D25 pinout

The Sub D25 male connector is connected to the same signals as the cable clamps. You can connect at your choice either using the clamps or the Sub D25 connector.

PIN Function PIN Function
1 0V (reference point) 14 0V (reference point)
2 0V (reference point) 15 EY analog input 2 (digital input In11)
3 EX analog input 1 (digital in In9) 16 0V (reference point)
4 5V auxiliary voltage output 17 12V power supply output
5 12V power supply output 18 In0 digital input (analog input 3)
6 In1 digital input (analog input 4) 19 In2 digital input (analog input 5)
7 In3 digital input  (analog input 6) 20 In4 digital input (analog input 7)
8 In5 digital input 21 In6 digital input
9 In7 digital input 22 Out0 digital output
10 Out1 digital output 23 Out2 digital output
11 Out3 digital output 24 Out4 digital output
12 Out5 digital output 25 Out6 digital output
13 Out7 digital output  
pinout of the 25 pin connector


Service USB plus

Sub D 25 connector top view

The outer metal shell is connected to the case and earthed.


RS232 pinout

The pinout is similar to standard IBM-PC PS232. There are four signal lines for RS232 usage, a 5V auxiliary voltage output and some general purpose input and output lines. All lines are protected against over and undervoltage up to ±24V an against short circuit.

Pin Function
1 Out8, digital output, 5V logic
2 Rx, RS232 receive data input, In12 digital input
3 Tx, RS232 transmit data output
4 In10, digital input (analog input 1)
5 GND (reference point, connected to 0V)
6 HSKi, RS232 input, remote station ready to receive, In8 digital input
7 HSKo, RS232 output, Service USB ready to receive, Out10 digital output
8 Out9, digital output, 5V logic
9 5V auxiliary voltage output


Service USB plus

Sub D 9 top view at Service USB Plus

The outer metal shell is connected to the case and earthed.


Digital outputs

The software supports 16 digital outputs for each connected interface, even though Service USB Plus hardware supports only 11 digital outputs. Service USB plus contains 8 power outputs which also can be used as pulse width modulated outputs. It contains two digital outputs with 5V logic level and one RS232 handshake output. Upon special instruction the lower 8 digital inputs can be switched as outputs so that there are 16 digital outputs. The outputs ( formerly the 8 lower input bits ) can switch to levels of 0V and 2,5V. They are best used for direct connected logic circuits or to drive the base of a bipolar transistor directly.


Digital inputs

The software supports 16 digital inputs for each connected interface, even though Service USB Plus hardware supports only 13 inputs. The lower eight inputs can be used with no restrictions and are lead through the cable clamps and the Sub D 25 connector. The upper eight bits share the pins with the analog inputs EX, EY and some signals at the Sub D 9 connector. Except RS232 input pins 2 and 6 at the Sub D 9 connector they all run on 0V/5V voltage level.

Bit Input Output
12 DB9 - 2 (RS232 level)  
11 DB25 - 15 + cable clamp  
10 DB9 - 4 DB9 - 7 (RS232 level)
9 DB25 - 3 + cable clamp DB9 - 8 (5V logic)
8 DB9 - 6 (RS232 level) DB9 - 1 (5V logic)
7 DB25 - 9 + cable clamp DB25 - 13 + cable clamp
6 DB25 - 21 + cable clamp DB25 - 25 + cable clamp
5 DB25 - 8 + cable clamp DB25 - 12 + cable clamp
4 DB25 - 20 + cable clamp DB25 - 24 + cable clamp
3 DB25 - 7 + cable clamp DB25 - 11 + cable clamp
2 DB25 - 19 + cable clamp DB25 - 23 + cable clamp
1 DB25 - 6 + cable clamp DB25 - 10 + cable clamp
0 DB25 - 18 + cable clamp DB25 - 22 + cable clamp

Allocation of the digital input- and output bits


Analog inputs

The software supports two inputs out of all eight analog inputs as fast inputs with no restrictions. These are the EX and EY inputs which can deliver 2000 values per second at 12 bit resolution. The other six analog inputs share the connectors with the digital inputs and can be mapped to the EX and EY channel.

Analog input Connector
7 DB25- 20, cable clamp In4 (shared with digital input bit 4)
6 DB25- 7, cable clamp In3 (shared with digital input bit 3)
5 DB25- 20, cable clamp In4 (shared with digital input bit 2)
4 DB25- 20, cable clamp In4 (shared with digital input bit 1)
3 DB25- 20, cable clamp In4 (shared with digital input bit 0)
2 DB25- 20, cable clamp In4 (shared with digital input bit 11)
1 DB9- 4 (together with digital input bit 10)
0 EX, DB25- 3, cable clamp EX (shared with digital input bit 9)


Mains supply

On the right side of the interface you will find a standard inlet connector for non-heating apparatus. The integrated wide range power supply can be supplied either by 115V or 230V (50 or 60Hz).

Service USB plus can be used the whole world over. Only the power cord is country specific. There are cables with EU, UK and US plugs available.



This connector complies to USB fullspeed with a data transfer rate of 12Mb/s. The maximal power consumption is 100mA. The 5V from USB is the power supply for the Service USB plus as well as the auxiliary voltage at the cable clamp and the Sub D connectors, which are protected with a resettable fuse.


The light emitting diodes

The twenty-four LEDs, which are corresponding to the input and output status, may flicker. Flickering only occurs, if your Macintosh is too busy to serve the USB. This does not affect the inputs and outputs, so you can ignore the flickering.
The LED „USB" is glowing at all times, if the Macintosh is connected correctly and 5V from USB connector appear on the cable clamp. The LED „12V" is connected to the 12V cable clamp and show the status of the built in power supply.


Technical Information

  • Dimensions: 175mm x 105mm x 45mm (width x depth x height)
  • Weight: 530g
  • Data transfer: USB full speed (12Mb/s)
  • USB current consumption: 100mA
  • Supply voltage: 115/230V main 50-60Hz 20W
  • Fuses: resettable
  • Digital inputs: 12
  • Digital input level: 0V / 5V
  • Digital input resistance: 4,7kΩ
  • Analog inputs: 8
  • Analog input level: 0 - 4,096V, 0-1mA, 0 - 200kΩ
  • Analog input resistance: 4,7kΩ
  • Analog resolution: 12 bit
  • Digital outputs: 8 power outputs + 8 logic outputs
  • Output voltage: 12V
  • Output current: 1.3A
  • Display: 26 LEDs
  • Cable clamps: 21 for wires and strands with cross selection 0,08-2,5 mm2
  • Maximum data rate: 2000 values per second for all digital and analog inputs simultaneously
  • Case protection category: IP30
  • Protection against reverse voltage, overloading and underloading up to ±24V as well as temperature protection.


Schematic diagrams


Service USB plus

Block diagram of Service USB Plus



Service USB plus

Circuit diagram of Service USB Plus