Bandai Hyper Shot grenade bug in Nestopia 1.40
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Author:  zeroone [ Sat Sep 24, 2016 3:37 pm ]
Post subject:  Bandai Hyper Shot grenade bug in Nestopia 1.40

There is no way to launch a grenade in Space Shadow using the Bandai Hyper Shot machine gun because Nestopia contains an incomplete implementation of the device. The port details can be found here. Bits 3 and 4 of port $4017 act like a Zapper and bit 1 of port $4016 acts like a third gamepad where the B button is the grenade launch button and the A button is unused. Although the Hyper Shot provides a full D-pad, Space Shadow--the only game designed for the Hyper Shot--is a rail shooter. The only direction required is Up, which advances the player to the next screen. Consequentially, Nestopia only supports the Up button, ignoring the rest including the B button. The snippet below, from NstInpBandaiHyperShot.cpp, contains a hack used to get most of the Hyper Shot working. First, the same data is provided to both ports instead of being split up as described above. And, second, instead of using a shift register for the gamepad bits, a single "move" bit is used for the Up button. This hack mostly works except that the player cannot launch grenades.

uint BandaiHyperShot::Peek(uint)
  uint data = (Poll() >= LIGHT_SENSOR ? 0x0 : 0x8);
  return data | fire | move;

Author:  koitsu [ Sat Sep 24, 2016 4:27 pm ]
Post subject:  Re: Bandai Hyper Shot grenade bug in Nestopia 1.40

Can you review the relevant NestopiaUE code and see if this still applies? If so, can you please file a GitHub Issues request that outlines this problem and/or include a patch or submit a pull req?

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