Just by adding a single jumper wire to the board and using an appropriate connector it makes possible to turn the AT is possible to turn the AT26-Chuck into a [S]NES to Atari converter with programmable auto fire support.

The code is mostly based on the #Digi:[S]NES project with some #defines to make the Arduino I/O functions compatible with CCS C:

#define uint16_t unsigned int16
#define uint8_t unsigned char
#define digitalWrite output_bit
#define digitalRead  input
#define HIGH 1
#define LOW 0

The auto fire is also borrowed from #Digi:[S]NES and it works on the contrary of the most common implementations either in software or in hardware: Instead of causing the actuation of the auto-fire button it causes the release of the button, thus simplifying the code to a single mask that causes the key to be released at a given rate. If the key is not pressed, then it makes no difference.

All of the buttons of the [S]NES controller are mapped to the single button in the Atari connector. To enable the auto fire for a given button just hold it down while the circuit is powered on. The auto-fire does not work for the directional buttons nor for Start and Select.

The connection to the SNES and NES controllers can be seen in the picture below. Notice that some wires are connected on the solder side of the board.