The Mule: Quickstart guide

This guide provides sufficient details for most uses to get The Mule up and running in the shortest possible time. For more detailed information including full technical specifications and advanced configuration details visit The Mule web site...

The Mule converts RS232 ASCII data into scancodes which the computer interprets as keystrokes. It can act as a 'virtual keyboard' by emulating a keyboard directly in hardware (KeyWedge Mode) or can utilise the USB port to achieve similar results utilising the Human Interface Driver (HID) provided with many modern operating systems.

The Mule can be used to simplify the interconnection of devices such as Barcode Scanners, Weighing Scales and other technical instrumentation to applications software even if the software authors had not anticipated the need for such interoperability.

The Mule can be used to allow one computer to control another. This has wide application in industrial, technical, scientific, manufacturing and testing environments.

Fitting the interface cable

Push the connector into the square hole in The Mule. Press firmly until the latch engages (listen for a slight click) and the cable cannot be pulled out again.

Removing the interface cable

Relieve the tension on the latch by pushing the cable firmly inward towards The Mule. To release the latch insert a straightened paper clip (or similar tool) into the small hole in the base of The Mule beneath the cable. The cable can then be easily withdrawn.

Green Lamp: Ready

The green lamp is lit when The Mule has powered up correctly and is waiting for RS232 data to arrive. The lamp is extinguished during the period it is unable to accept further data while it is transmitting to the KeyWedge or USB cables.

Red Lamp: Overload

The Mule continuously monitors the voltage of the power drawn from the PC. If The Mule is configured to power the RS232 device from the computer the Overload Lamp will light if the computer cannot provide sufficient power (a brief indication when the computer powers up is normal). If this happens you should reconfigure the links inside The Mule and the RS232 device to use an external power source. Further details about advanced configuration options for The Mule can be found on our web site.


Connecting The Mule

The Mule can be fitted with either of two cable types: KeyWedge and USB. KeyWedge works with any computer using a IBM compatible Keyboard. It does not need software drivers and can work with any operating system such as MSDOS which may not have USB drivers.

Some computers, particularly laptops, do not have an external connector for a keyboard. The USB option can be used provided the computer operating system supports the USB port with a HID (Human Interface Device) driver. Many recent operating systems provide this support- MS Windows, MAC, Linux, Sun, HP Unix for example.

Both KeyWedge and USB interfaces send data which the computer interprets as keystrokes.


  1. Switch the computer off
  2. Disconnect the keyboard from the rear of the computer taking note of which connector it was connected to. Some computers color code the connectors- the keyboard is purple. The green connector (Same size and shape) is for the mouse do not use this connector for The Mule. The keyboard on older computers may be fitted with a larger connector (5 pin DIN). If you have this type of connector you will need to purchase a keyboard adapter set.
  3. Connect the male connector on the KeyWedge cable to the socket previously occupied by the keyboard.
  4. Connect the keyboard to the free socket on the KeyWedge cable.
  5. Switch the computer on and check that the keyboard operates normally. The green Ready Indicator lamp on The Mule should be illuminated.


  1. It is not necessary to switch the computer off
  2. Fit the USB cable to any free USB port on the computer.
  3. After a few seconds the computer should detect the device and start to install the correct driver. The driver is part of the computer operating system it is not provided with The Mule. Some operating systems may need the original install disks to complete the installation. If you intend to use The Mule on more than one USB port some systems require you to install the driver on each port. Once the initial install process is completed you should not normally need to repeat the process. The next time The Mule is connected the computer will automatically reconnect.
  4. After installation completes check the keyboard operates normally. The green Ready Indicator on The Mule should be illuminated.

External Power connector

The Mule is usually powered from power drawn from the host computer. A connector is provided if it is necessary to use an external power supply unit to power a device connected to The Mule. For further details about this optional facility see the full technical details on our web site.


RS232 Interface

Connector and Pinout
  1. Not connected
  2. Receive data (The Mule input)
  3. Transmit data (The Mule output)
  4. Optional power out (see text)
  5. Ground
  6. Not connected
  7. RTS (The Mule output)
  8. CTS (The Mule input)
  9. Connected to pin 4 (see text)
The Mule connector

Device power source

Pins 4 and 9 are interconnected inside The Mule. Either may be used to source power to drive an external RS232 device. These pins have been chosen to be compatible with the normal DTR function of pin 4.

In its default configuration pins 4 and 9 are connected to a voltage regulator inside The Mule. If a unregulated voltage (9-12v) is applied to the External Power connector a regulated 5 volt source will appear at pins 4 and 9. 300mA can be drawn continuously and up to 1A for short intermittent periods.

If you intend to use this optional feature more technical detail can be found on the web site.

RS232 data format

The default data format is: 9600 baud, 8 data bits, no parity, 1 Stop bit.

RS232 handshake

It is recommended that The Mule be operated with a proper RTS/CTS handshake. This will ensure no data loss or transmission problems.

Missing characters, double characters, incorrect characters, unusual symbols appearing on the screen, computer lockup or beeping sounds from the computer all indicate a handshaking problem.

If the incoming data stream conforms to all of the constraints listed below The Mule may be operated successfully without a handshake.

  • A data burst of fewer than 50 characters.
  • The period between each character in the burst is less than 100mS
  • The period between each burst is more than 100ms and is sufficient to allow all the previous data burst characters to be sent to the computer.
...this is typical of the data structure emitted by a barcode scanner or similar.

Full details on RS232 handshaking options for The Mule can be found on the web site.


Help and Support

Detailed operations, up to date technical information, lists of scancodes and more can be found on our web site.

If you have a question not answered by the web site or you need help then please contact the support desk by emailing from the web site.

Keywedge and The Mule are trademarks owned by Altek Instruments Ltd UK.        © 2004

The Mule is a low powered digital device and in normal circumstances is unlikely to cause any significant radio (or any other) interference. The following statements are made in order to comply with legislation in relevant jurisdictions.

FCC Compliance Statement

The Mule is a low powered digital device and in normal circumstances is unlikely to cause any significant radio interference. However the The Federal Communications Commission (FCC) requires all digital devices and peripherals to carry an appropriate statement regarding its compliance under the FCC rules.

The Mule complies with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates and can radiate radio frequency energy and if not installed and used in accordance with the manufacturers instructions may cause harmful interference to radio communications.

If the equipment is to be used in a residential area and unacceptable interference to Radio and TV reception is caused (which can be determined by switching the equipment off and on) the user will be required to correct the interference at his own expense. The user is encouraged to try to correct interference by one or more of the following measures:

  1. Reorientate or relocate the receiving antenna or the digital device.
  2. Increase the separation between the digital device and receiver.
  3. Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
  4. Consult an experienced radio/TV technician for help.

EU Electromagnetic Compatibility Compliance Statement

EMC Compatibility Mark

The manufacturers of The Mule, Altek Instruments Ltd, Walton-on-Thames, UK declare The Mule computer interface to comply with all relevant European Community legislation and to conform to the maximum permitted levels for Electromagnetic Radiation defined in The Electromagnetic Compatibility (EMC) Directive 89/336/EEC, the amending Directive 92/31/EEC and the UK Electromagnetic Compatibility Regulations Statutory Instrument SI 1992/2372