128 lines
2.9 KiB
C
128 lines
2.9 KiB
C
//
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// Author: Jeremy Rand
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// Date: July 20, 2012
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//
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// This is the implementation for the Curta emulator UI.
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//
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#include <stdio.h>
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#include "joystick.h"
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#define PREAD 0xFB1E
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#define ROM_SWITCH 0xC082
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#define RAM_SWITCH 0xC080
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#define BTN0 0xC061
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#define BTN1 0xC062
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#define JOYSTICK_CENTER 127
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#define JOYSTICK_THRESHOLD 60
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#define LOWER_THRESHOLD (JOYSTICK_CENTER - JOYSTICK_THRESHOLD)
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#define UPPER_THRESHOLD (JOYSTICK_CENTER + JOYSTICK_THRESHOLD)
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static uint8_t joystickTemp;
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static bool isButtonPressed(int8_t buttonNum)
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{
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if (buttonNum) {
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__asm__ volatile("LDA %w", BTN1);
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__asm__ volatile("STA %v", joystickTemp);
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} else {
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__asm__ volatile("LDA %w", BTN0);
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__asm__ volatile("STA %v", joystickTemp);
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}
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return ((joystickTemp > 127) ? true : false);
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}
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static uint8_t joystickLeftRight(void)
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{
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__asm__ volatile("BIT %w", ROM_SWITCH);
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__asm__ volatile("LDX #0");
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__asm__ volatile("JSR %w", PREAD);
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__asm__ volatile("STY %v", joystickTemp);
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__asm__ volatile("BIT %w", RAM_SWITCH);
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return joystickTemp;
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}
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static uint8_t joystickUpDown(void)
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{
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__asm__ volatile("BIT %w", ROM_SWITCH);
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__asm__ volatile("LDX #1");
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__asm__ volatile("JSR %w", PREAD);
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__asm__ volatile("STY %v", joystickTemp);
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__asm__ volatile("BIT %w", RAM_SWITCH);
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return joystickTemp;
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}
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void getJoystickState(tJoyState *state)
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{
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static bool readLeftRight = true;
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static uint8_t axisLeftRight = 127;
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static uint8_t axisUpDown = 127;
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tJoyPos pos = JOY_POS_CENTER;
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if (readLeftRight) {
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int temp = joystickLeftRight(); // Get left/right position
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temp *= 3;
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temp /= 4;
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axisLeftRight /= 4;
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axisLeftRight += temp;
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readLeftRight = false;
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} else {
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int temp = joystickUpDown();
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temp *= 3;
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temp /= 4;
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axisUpDown /= 4;
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axisUpDown += temp;
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readLeftRight = true;
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}
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if (axisLeftRight < LOWER_THRESHOLD) {
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pos = JOY_POS_LEFT;
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} else if (axisLeftRight > UPPER_THRESHOLD) {
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pos = JOY_POS_RIGHT;
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}
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state->button0 = isButtonPressed(0);
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state->button1 = isButtonPressed(1);
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if (axisUpDown < LOWER_THRESHOLD) {
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switch (pos) {
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case JOY_POS_LEFT:
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pos = JOY_POS_UP_LEFT;
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break;
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case JOY_POS_RIGHT:
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pos = JOY_POS_UP_RIGHT;
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break;
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default:
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pos = JOY_POS_UP;
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break;
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}
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} else if (axisUpDown > UPPER_THRESHOLD) {
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switch (pos) {
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case JOY_POS_LEFT:
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pos = JOY_POS_DOWN_LEFT;
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break;
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case JOY_POS_RIGHT:
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pos = JOY_POS_DOWN_RIGHT;
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break;
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default:
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pos = JOY_POS_DOWN;
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break;
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}
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}
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state->position = pos;
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// Add in a bit of extra delay also
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for (pos = 0; pos < 100; pos++)
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;
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}
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