Genesis-Plus-GX/core/input_hw/paddle.c

120 lines
3.8 KiB
C

/***************************************************************************************
* Genesis Plus
* Sega Paddle Control support
*
* Copyright (C) 2007-2023 Eke-Eke (Genesis Plus GX)
*
* Redistribution and use of this code or any derivative works are permitted
* provided that the following conditions are met:
*
* - Redistributions may not be sold, nor may they be used in a commercial
* product or activity.
*
* - Redistributions that are modified from the original source must include the
* complete source code, including the source code for all components used by a
* binary built from the modified sources. However, as a special exception, the
* source code distributed need not include anything that is normally distributed
* (in either source or binary form) with the major components (compiler, kernel,
* and so on) of the operating system on which the executable runs, unless that
* component itself accompanies the executable.
*
* - Redistributions must reproduce the above copyright notice, this list of
* conditions and the following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************************/
#include "shared.h"
static struct
{
uint8 State;
uint8 Counter;
} paddle[2];
void paddle_reset(int port)
{
input.analog[port][0] = 128;
paddle[port>>2].State = 0x40;
paddle[port>>2].Counter = 0;
}
INLINE unsigned char paddle_read(int port)
{
/* FIRE button status (active low) */
unsigned char temp = ~(input.pad[port] & 0x10);
/* Pad index */
int index = port >> 2;
/* Clear low bits */
temp &= 0x70;
/* Japanese model: automatic flip-flop */
if (region_code < REGION_USA)
{
/* two I/O port reads are required to fully read paddles state on control ports 1 & 2 so using two read access latency for switching should be safe */
/* note: real paddle switching time is approx. 62.5 us period according to https://www.raphnet.net/electronique/sms_paddle/index_en.php#4 */
if (++paddle[index].Counter > 2)
{
paddle[index].Counter = 0;
paddle[index].State ^= 0x40;
}
}
if (paddle[index].State & 0x40)
{
/* return higher bits */
temp |= (input.analog[port][0] >> 4) & 0x0F;
}
else
{
/* return lower bits */
temp |= input.analog[port][0] & 0x0F;
/* set TR low */
temp &= ~0x20;
}
return temp;
}
INLINE void paddle_write(int index, unsigned char data, unsigned char mask)
{
/* update bits set as output only */
paddle[index].State = (paddle[index].State & ~mask) | (data & mask);
}
unsigned char paddle_1_read(void)
{
return paddle_read(0);
}
unsigned char paddle_2_read(void)
{
return paddle_read(4);
}
void paddle_1_write(unsigned char data, unsigned char mask)
{
paddle_write(0, data, mask);
}
void paddle_2_write(unsigned char data, unsigned char mask)
{
paddle_write(1, data, mask);
}