Mouse right button

[OldAtarian]

Does anyone know how it works? How is the mouse port different from the joystick port to allow for 2 buttons independent of one another?

[Rybags]

Standard Atari ports have 4 directions, fire, 2 paddles, +5V, GND.

 

ST doesn't have Pot inputs on the 9-pin ports so they can use the spare line for second mouse button.

 

IIRC, there's a project around that allows modifying an ST mouse so you can also detect the right button on 8-bit computers.

[OldAtarian]

I found a diagram of the pins and it says that the second button is read through pin 9 of the connector, which is unused in a regular joystick port. If I were to do something like solder a jumper wire on the underside of an 8-bit motherboard from pin 9 on stick(0) to pin 6 on stick(1) (the fire button) and then write a short program that polls both joystick ports only looking for activation of pin 6 on the second one, then could I use the second button of the ST mouse?

[Rybags]

Mouse button 1 uses the joystick trigger line.

 

The ball x/y goes through the 4 joystick directional lines.

 

There aren't "unused" pins on the 8-bit controller ports, the unused ones with a joystick correspond to the 2 paddle inputs.

[OldAtarian]

Mouse button 1 uses the joystick trigger line.

 

The ball x/y goes through the 4 joystick directional lines.

 

There aren't "unused" pins on the 8-bit controller ports, the unused ones with a joystick correspond to the 2 paddle inputs.

 

Yes. Mouse button one uses the joystick trigger line on the port that it's plugged into. I'm talking about using the trigger line on the other joystick port for the second button, not the first one.

 

9 way DB9P plug

Port 0 is configured for mouse operation

Port 1 is the second joystick interface

Pin-----Joystick function--------Mouse / Joystick 0 function

1-------Up-------------------------XB/Up

2-------Down---------------------XA/Down

3-------Left------------------------YA/Left

4-------Right----------------------YB/Right

5-------reserved------------------n.c

6-------Fire------------------------left button/Fire

7-------Power--------------------+5V

8-------Gnd----------------------Ground

9-------n.c.-----------------------right button/Joystick 1 fire

 

This is what I found and it says pin 5 is normally reserved (presumably for paddles) but is not connected in the ST. It also says pin 9 is not connected in other Atari systems but is used for the right button in the ST mouse port and is connected to joystick 1 fire button.

 

The wiring diagram on this page even shows pin 9 as disconnected in the 2600 and used as the left button in the 7800, so if it's disconnected in the 2600 and is the left button in the 7800, how can it be used for paddles? It looks to me that Atari wired the mouse port the same way it's wired on the 7800 to take the second button into account. It is NOT wired the same way as a 2600/400/800 port. I've known it wasn't wired the same way as a 2600/400/800 joystick port since the ST first came out, but you're trying to tell me that it is which is wrong. I also see no mention in any diagram of any pin being reserved specifically for paddles unless it's pin 5. If you need a pin for paddles, you also need one for driving controllers because they send a completely different signal, so which pin would that be?

 

http://www.epanorama.net/documents/joystick/tvgames.html#2600

Edited October 24, 2010 by OldAtarian

[Rybags]

5/9 are the paddle inputs.

 

The 7800 routes the controller inputs slightly differently depending if in 2600 or 7800 mode.

 

I'm just about sure there's a mod around that just lets the computer read MB2 via a Pot input, and still work on the ST. It involves changing a resistor value.