mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
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145 lines
3.9 KiB
C
145 lines
3.9 KiB
C
/***************************************************************************************
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* Genesis Plus
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* XE-A1P analog controller support
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*
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* Copyright Eke-Eke (2007-2011)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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****************************************************************************************/
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#include "shared.h"
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static struct
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{
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uint8 State;
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uint8 Counter;
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uint8 Latency;
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} xe_a1p;
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void xe_a1p_reset(void)
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{
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input.analog[0][0] = 128;
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input.analog[0][1] = 128;
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input.analog[1][0] = 128;
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xe_a1p.State = 0x40;
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xe_a1p.Counter = 0;
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xe_a1p.Latency = 0;
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}
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unsigned char xe_a1p_read()
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{
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unsigned int temp = 0x40;
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/* Left Stick X & Y analog values (bidirectional) */
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int x = input.analog[0][0];
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int y = input.analog[0][1];
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/* Right Stick X or Y value (unidirectional) */
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int z = input.analog[1][0];
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/* Buttons status (active low) */
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uint16 pad = ~input.pad[0];
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/* Current 4-bit data cycle */
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/* There are eight internal data cycle for each 5 acquisition sequence */
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/* First 4 return the same 4-bit data, next 4 return next 4-bit data */
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switch (xe_a1p.Counter >> 2)
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{
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case 0:
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temp |= ((pad >> 8) & 0x0F); /* E1 E2 Start Select */
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break;
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case 1:
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temp |= ((pad >> 4) & 0x0F); /* A B C D */
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break;
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case 2:
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temp |= ((x >> 4) & 0x0F);
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break;
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case 3:
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temp |= ((y >> 4) & 0x0F);
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break;
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case 4:
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break;
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case 5:
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temp |= ((z >> 4) & 0x0F);
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break;
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case 6:
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temp |= (x & 0x0F);
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break;
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case 7:
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temp |= (y & 0x0F);
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break;
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case 8:
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break;
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case 9:
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temp |= (z & 0x0F);
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break;
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}
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/* Get current internal cycle (0-7) */
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unsigned int cycle = xe_a1p.Counter & 7;
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/* TL indicates which part of data is returned (0=1st part, 1=2nd part) */
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temp |= ((cycle & 4) << 2);
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/* TR indicates if data is ready (0=ready, 1=not ready) */
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/* Fastest One input routine actually expects this bit to switch between 0 & 1 */
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/* so we make the first read of a data cycle return 1 then 0 for remaining reads */
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temp |= (!(cycle & 3) << 5);
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/* Automatically increment data cycle on each read (within current acquisition sequence) */
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cycle = (cycle + 1) & 7;
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/* Update internal cycle counter */
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xe_a1p.Counter = (xe_a1p.Counter & ~7) | cycle;
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/* Update internal latency on each read */
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xe_a1p.Latency++;
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return temp;
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}
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void xe_a1p_write(unsigned char data, unsigned char mask)
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{
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/* update bits set as output only */
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data = (xe_a1p.State & ~mask) | (data & mask);
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/* look for TH 1->0 transitions */
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if (!(data & 0x40) && (xe_a1p.State & 0x40))
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{
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/* reset acquisition cycle */
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xe_a1p.Latency = xe_a1p.Counter = 0;
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}
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else
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{
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/* some games immediately write new data to TH */
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/* so we make sure first sequence has actually been handled */
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if (xe_a1p.Latency > 2)
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{
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/* next acquisition sequence */
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xe_a1p.Counter = (xe_a1p.Counter & ~7) + 8;
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/* 5 sequence max with 8 cycles each */
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if (xe_a1p.Counter > 32)
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{
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xe_a1p.Counter = 32;
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}
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}
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}
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/* update internal state */
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xe_a1p.State = data;
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}
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