Port number for a Cedrus device?

[JEC]

Okay. We've spoken with Cedrus in the past, and they're very reluctant to share the communications protocol that their button boxes use. And unforunately, we don't have any of their equipment here in the shop to test for ourselves.

So here are a few suggestions.

1. Check your operating manual and see what baud rate the box is probably communicating at. I'd expect that you'd see either '9,600 or 19,200' as choices.

2. If the box has a setting for 'simple' communications, rather than a continuous stream of data, pick the simple mode.

3. Then, open a program called 'hyperterminal' on your computer, and plug in the box and power it up. Create a new connection in hyperterm which matches the settings your box needs to communicate.

4. Press some buttons on the box and watch to see if you see any characters appear on the terminal screen. If you do, great.

4.5 Disconnect the button box from your computer, but keep hyperterm running.

5. Then, open a tool called 'IOTest.' It comes free with every copy of MediaLab or DirectRT. It's buried in the tools folder.

6. In the 'port name' field, enter the decimal value of the com port you're using. COM1 is generally found at 1016 (3F8 hex). COM2 is 2F8, COM3 is 3E8. 2F8 converts to decimal 760. 3E8 is 1000.

*** Note that if you're using an external USB - Serial converter dongle, all bets are off. The addresses listed above refer to physical circuitry inside your computer. Since the USB device emulates a serial port, you won't be able to find an address this way. ***

7. Take a look at the port value box of IOTest. It will list a value, perhaps zero, for when the port is at rest.

8. Plug in the button box, press some buttons, and see if the port value changes. If it does, you're in luck. All you need to do is write your MediaLab script to accept *that particular value* as a valid answer. Check your manual for more details on how to do this.

* * * What we've been trying to do thus far is coax the button box to emit a single byte of data when a button is pressed. If we can get a single byte of data, we can work with it in DirectRT or MediaLab.

If you have access to an oscilloscope, this entire process can be vastly simplified, just by monitoring the box's serial transmissions to your computer. Serial port pins 2 and 3 would be especially interesting to probe, with reference to ground.

If, on the other hand, the box is emitting a constant stream of data which changes in a complex way for each button press, MediaLab and DirectRT likely won't be able to understand it.

Hope this helps.

John