Thanks for the offer. I think I'll pass for now.

Or I can sell you one of these:

http://www.midisolutions.com/prodfsw.htm

Didnt really work in my setup. But tap tempo is one of its features.

...as they've done to so many in the past.

And just like that, Nordloef and Saskrotch crush my dreams...

tap A on tempo

Really? How do you access it? (I don't have my Game Boy on me at the moment.)

but lsdj's got a tap tempo function already

Interesting. Thanks for the link. It would be nice to retain the other midi functions (or at least some of them) and keep the in/out jacks. Do you think I'd need 2 Arduinos for that?

would you want to retain any of the midi functions? like, midi in and out jacks, or would you just want it to be a clock source?

i can see this being really easy to do.

No, but a quick google turned this up:

http://umlautllama.com/projects/arduino/s/TapTempo.pde

I think there are a few digital inputs left ona  stock arduinoboy right? So youd need to hack sync in mode to use this.

I'm building a new Arduinoboy box, and I'm thinking about modifying the Arduino code/schematic to support a tap tempo button. The general idea: Rather than using the box to midi sync the Game Boy with another device, simply send a midi signal to the Game Boy by tapping the tempo with button on the box.

Has anyone ever tried this?