Need advice on tracing controller signals

[acharris]

HI all, I am teaching myself some electronic knowledge, so I can mess with projects and mods, and I have learned to solder and basic stuff, but one thing I would like some advice on is how to read controller input signals with a multi-meter. I am not 100% sure how you read the signals from the controller or the console port, if it ohms to measure or not. I assume the game must be running and the controller used to send a signal.

 

Any basic advice for me to try would be appreciated, as I am trying to learn and would rather advice from some knowledgable people, than every joe bloggs I know who claim to know about electronics, and they don't know that much, as I have more knowledge than a few people I know (which don't say much since I am learning and only have basic knowledge)

 

Thanks in advance.

 

Anthony

[A.J. Franzman]

It depends on what system and controller's signals you're trying to read. For a simple example, Atari 2600 joysticks merely ground one wire for each direction and the fire button. More recent systems, however, have digitally encoded controls so many different buttons and analog inputs can be carried on just a few wires. This type of signal can not be read with just a multimeter.

Edited August 17, 2007 by A.J. Franzman

[+Stephen Moss]

As A.J. Franzman stated some controllers such as basic joysticks rely on just a supply voltage and a simple logic state for outputs while others like the Jaguar work on row column addressing and use four control lines.

If you are interested in a specific controller you may be better off doing a forum search as someone may have enquired about it before or ask about it specifically, in general tems what I will say is this...

 

1) All Atari's appear to work on active low, in other words 0V is the active state for both inputs and outputs and +5V (high) is the inactive or default state.

2) You should measure voltage, however depending on the mark space ratio/pulse duty factor of the signals your DVM may provide and average voltage reading somewhere between 0V and 5V.

3) For more complicated controllers like the Jaguar or Playstation your really need a multichannel storage oscilloscope or ideally a logic analyzer if a web search does not yeild any information on how they operate.

4) As storage 'scopes and Logic Analysers are expensive and not available to everyone so you may want to think about simple logic probes which you can purchse or make youself as depending on how you do it you only need an led or two for each channel and two connections for power which you get from the system you are looking at, however as with the DVM rapidly changing signals only give a average reading in that the LED may be on but appear dimmer than those LEDs that are one in a constant state or change state briely with long constant periods and thus appear to be permanently in a constant state.

[acharris]

Thanks for the replies guys. Much appreciated.