Macintosh parallel input and output

USB digital I/O Cards

Easydaq sell USB relay cards (4, 8, and 24 relays) connected by wires and one connected by wireless
(USBXBeeTX Transceiver module and XBee8PRMx wireless relay card) with Macintosh software.

Chris Nelms has posted an article showing how to operate the relay card
from the Mac OSX Terminal Command Line.
You may need to download a Mac OSX driver from the FTDI site for the USB chip.
GigaTechnology developed a card with a USB interface and 24 parallel input/output ports. This card and a range of i/o accessory cards is available from Elexol electronic solutions, including a relay card, an opto isolator card, a switch card and a led display card
The USB I/O 24 card uses an FTDI USB to serial chip. The USBIO 24 Mk3 uses the FT245BM chip.

You can download a Mac OSX driver from the FTDI site for FT8U232AM, FT8U245AM, FT232BM and FT245BM devices.
Step 1 Install Driver
  • Download the driver from FDTI and install it
Step 2 Connections
  • Connect your external device using
  • a breadboard (right), or
  • an i/o card (right below)

Simple I/O card

We made a simple i/o card with

  • 8 connectors for output
  • 8switches for input, and
  • 8 leds for display

Elexol have released a range of i/o cards

  • 8 relay output board with 8 relays
  • 8 opto-isolated input board
  • 8 switch input board, and
  • 8connector board

Controlling an inexpensive R/C toy
Above: Radio controlled car with Swann spycam (includes radio link) on top Radio control handset connected to Macintosh with USB 24 I/0
  • left - hand controller
  • bottom - voltage change circuit
  • top - USB 24 I/O
  • bottom right - simple I/O card
Step 3 Wiring
  • Push buttons on controller typically pull a resister to 0 volts when depressed
  • The voltage may be different to the voltage on the USB 24 I/O card
  • The controller on the left ran on 9 volts
  • The USB 24 I/O card is 5 volts
  • To step from a 5v circuit to a 9v circuit we inserted a 2803 octal peripheral driver chip between the terminals of the simple i/o card and the switches on the r/c handset, such that the open collector transistors in the chip acted across the terminals of the switch to pull the voltage to 0. Voltage for the chip comes from the USB 24 I/O card via the simple i/o board
  • It would have been neater to have used a bread board.
  • It would have been much neater to have used an Elexol relay card, except that it requires q 12 volt supply.
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Page updated Tuesday 26th January 2009