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hacking Battletoads to read input from the Famicom Exp port
http://forums.nesdev.com/viewtopic.php?f=2&t=16727
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Author:  Pokun [ Thu Nov 23, 2017 2:27 pm ]
Post subject:  Re: hacking Battletoads to read input from the Famicom Exp p

Gilbert wrote:
it may even be possible that if you modify the console by changing the hardwired P2 pad to some other controllers the START button may work too.
Yeah probably it's just the shift register that spits out zeroes instead of the START and SELECT data in the hardwired controller II when reading it. If you somehow connect a controller I (or a NES controller) on the PCB connector START and SELECT will probably work like on an AV Famicom or NES. It would be interesting to add a microphone to a controller I and a PCB connector from a controller II to get a Famicom that has both a microphone and START/SELECT buttons.

Author:  rainwarrior [ Thu Nov 23, 2017 3:32 pm ]
Post subject:  Re: hacking Battletoads to read input from the Famicom Exp p

Yes the Famicom controller 2 has the same 4021 8-bit shift register as the others, it just has the pins for SELECT and START hard wired to 5V. You could relatively easily reconnect those to two new buttons.

I don't know what you mean about "add a microphone to controller 1", though. There's only 1 data line that's ever listened to for the mic (D2 on $4016), so having a second microphone won't be able to do anything. You'd also have to replace its cord with one that has more wires to accomodate the extra line. (The mic is a dedicated line, it's not part of the serial input from D0.)

Author:  Pokun [ Thu Nov 23, 2017 4:45 pm ]
Post subject:  Re: hacking Battletoads to read input from the Famicom Exp p

I don't mean add another microphone, the goal is to add START and SELECT buttons on the second controller while keeping the microphone.
I mean to use a spare controller I or NES controller and add a microphone to it and connect it instead of controller II, not instead of controller I. I figured it would be easier to add a microphone to a controller than to add good START and SELECT buttons to a controller II. You would need to steal the connector from a controller II in that case though (a controller I connector won't fit).

Author:  rainwarrior [ Thu Nov 23, 2017 5:05 pm ]
Post subject:  Re: hacking Battletoads to read input from the Famicom Exp p

Ah, yes that makes sense.

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