From 9ecd65467232071b18a7c6f782a22264046ebf45 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Sat, 22 Jul 2023 13:58:05 +0100
Subject: Joystick support

---
 src/joy.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 src/joy.c

(limited to 'src/joy.c')

diff --git a/src/joy.c b/src/joy.c
new file mode 100644
index 0000000..cda2fcf
--- /dev/null
+++ b/src/joy.c
@@ -0,0 +1,123 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <pc.h>
+#include <dos.h>
+
+#include "vga.h"
+#include "keyb.h"
+#include "control.h"
+
+#include "joy.h"
+
+#define PORT 0x201
+
+#define BUTTON1 0x10
+#define BUTTON2 0x20
+#define AXISX   1
+#define AXISY   2
+
+#define TIMEOUT 16000
+
+static uint16_t j_up, j_down, j_left, j_right;
+
+static uint16_t read_axis(uint8_t axis)
+{
+    uint16_t i;
+
+    disable();
+    outportb(PORT, 0xff);
+    for (i = 0; i < TIMEOUT; i++)
+        if (!(inportb(PORT) & axis))
+            break;
+    enable();
+
+    return i;
+}
+
+static uint8_t calibrate(uint16_t *v, uint16_t *h)
+{
+    while (1)
+    {
+        if (keys[KEY_ESC])
+        {
+            while (keys[KEY_ESC])
+                wait_vsync();
+            return 0;
+        }
+
+        *v = read_axis(AXISY);
+        *h = read_axis(AXISX);
+
+        if (!(inportb(PORT) & BUTTON1))
+        {
+            while (!(inportb(PORT) & BUTTON1))
+                wait_vsync();
+            return 1;
+        }
+
+        wait_vsync();
+    }
+}
+
+uint8_t joy_detect()
+{
+    if (read_axis(AXISX) == TIMEOUT)
+        return 0;
+
+    printf("Joystick detected!\n");
+
+    printf("Please move UP + LEFT and press BUTTON 1 (ESC to abort)\n");
+    if (!calibrate(&j_up, &j_left))
+        return 0;
+    printf("Please move DOWN + RIGHT and press BUTTON 1 (ESC to abort)\n");
+    if (!calibrate(&j_down, &j_right))
+        return 0;
+
+#ifdef DEBUG
+    printf("Joystick reads: up=%04d, down=%04d, left=%04d, right=%04d\n",
+           j_up, j_down, j_left, j_right);
+#endif
+
+    j_up += j_up >> 4;
+    j_down -= j_down >> 4;
+    j_left += j_left >> 4;
+    j_right -= j_right >> 4;
+
+#ifdef DEBUG
+    printf("      Adjusted: up=%04d, down=%04d, left=%04d, right=%04d\n",
+           j_up, j_down, j_left, j_right);
+
+    printf("(press X to continue)\n");
+    while (!keys[KEY_X])
+        wait_vsync();
+#endif
+
+    return 1;
+}
+
+uint8_t joy_read()
+{
+    uint8_t r = CTL_NONE;
+    uint8_t b;
+    uint16_t v;
+
+    b = inportb(PORT);
+    if (!(b & BUTTON1))
+        r |= CTL_FIRE1;
+    if (!(b & BUTTON2))
+        r |= CTL_FIRE2;
+
+    v = read_axis(AXISY);
+    if (v <= j_up)
+        r |= CTL_UP;
+    if (v >= j_down)
+        r |= CTL_DOWN;
+
+    v = read_axis(AXISX);
+    if (v <= j_left)
+        r |= CTL_LEFT;
+    if (v >= j_right)
+        r |= CTL_RIGHT;
+
+    return r;
+}
-- 
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