Monday, November 05, 2007

(More) Synthcart control

Synthcart is a cartridge for the Atari 2600 written by Paul Slocum. The program uses the Atari 2600 keypad controllers as an interface for users to trigger notes and beats on the video game console.

Consider how the Atari keypad operates. The keypad itself has twelve buttons ordered in four rows of three columns. Seven pins of the nine pin connector are used as a means of gathering the current state of the twelve-button keypad. Each row and each column are assigned a pin. The row pins are acting as digital inputs and the column pins are acting as digital outputs.

The console effectively scans through each column by holding the column pin low and reading the digital state of the four row pins. If the state of a given row is read as being low, then that row is electrically connected to the column pin by the physical act of pressing the button. This process is repeated until all three columns are read. It is the combination of column pin and row pin that determines the key that is being read, as follows:
       pin 5   pin 9   pin 6
pin 1 key 1 key 2 key 3
pin 2 key 4 key 5 key 6
pin 3 key 7 key 8 key 9
pin 4 key * key 0 key #

It is possible to electrically emulate this pressing of buttons. The process involves the 4016 quad analog switch IC.

Example video:

I am sure that there is more of this to come.


MikMo said...

I think there's an example in the Arduino playground where two 4051 IC's are used to make a 8 by 8 matrix.

Found it:

Sebastian Tomczak said...

cool cool. yeah the 4051 is very useful. a shop around the corner from me recently had a bunch on special for AU$0.80! so this is very good news for me.