2-button Arcade stick board

[astroguy]

Just finished putting together and playing with a prototype board to plug in arcade sticks and buttons.  Works with 2600+ and a real 7600 with two buttons.  I added an adjustable 555 timer through a transistor to enable turbo-fire on the left button.  There are two logic gates to control the turbo fire with the main button push. 

 

Next is to turn the prototype into a circuit board, but I'm very happy with it.  I installed the board in an 8-bitdo arcade stick and it's great fun on games like Asteroids and Asteroids Deluxe.  It's nice to tune in the auto-fire get a nice cadence for blasting those rocks!

[astroguy]

Attached is the schematic that was developed in parallel with the prototyping board.  Feedback and comments are welcome. 

 

I'll probably swap out the B50K variable resistor with something smaller as having a timer with a cadence longer than 1-sec is probably not necessary. 

 

The one part I don't like is I'm using a TTL logic hex-inverter that only seems to work with a ~2K pull down resistor that was larger than I expected based on the data-sheets.  I hoping to pick up some CMOS replacements that should remove uncertainty. 

 

I do not keep 620 ohm resistors in stock so I substituted with a 10K + 680 resister in parallel.

[astroguy]

oh.. and a typo.  The 0.1 pF capacitor on the 555 should be 10nF.

[astroguy]

Whipped up a board to hold the arcade board with a few buttons and an arcade stick.   Now I need to make some fun cover art and file down some corners for a nice flush finish.   I also ordered a new batch of LS logic chips so I can replace the NOR-HEX gates with a single AND gate.  Part of the fun is problem solving with whatever I have lying around.  I think 1/2 of the parts I used came from parts salved from a discarded automated espresso maker.