From 681bd85b0e3144e0dcc77a8cbe00747e8d4716de Mon Sep 17 00:00:00 2001
From: Väinö Kauppila <vaino@vke.fi>
Date: Mon, 20 Apr 2026 15:24:16 +0300
Subject: snake uart recv SM

---
 fw/snake.c | 41 +++++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 14 deletions(-)

(limited to 'fw')

diff --git a/fw/snake.c b/fw/snake.c
index 879acf0..c875b1e 100644
--- a/fw/snake.c
+++ b/fw/snake.c
@@ -24,6 +24,7 @@ static __near uint8_t food_x;
 static __near uint8_t food_y;
 static __near uint8_t score;
 static volatile __near uint8_t ovf_count;
+static __near uint8_t input_state;  /* 0=idle, 1=got ESC, 2=got ESC+[ */
 
 void isr(void) __interrupt(0) {
     if (INTCON & 0x04) {
@@ -47,20 +48,31 @@ static uint8_t uart_recv(void) {
     return UART_RX;
 }
 
-static uint8_t uart_getc(void) {
-    while (UART_STATUS & 0x02);
-    return UART_RX;
-}
-
+/* Non-blocking state machine — drains the whole FIFO each frame.
+ * Handles both ESC [ x (CSI) and ESC O x (SS3) cursor key modes.
+ * Never blocks, so a stray ESC can't freeze the game. */
 static void handle_input(void) {
-    uint8_t c = uart_recv();
-    if (c != 0x1B) return;
-    if (uart_getc() != '[') return;
-    switch (uart_getc()) {
-        case 'A': if (direction != DIR_DOWN)  direction = DIR_UP;    break;
-        case 'B': if (direction != DIR_UP)    direction = DIR_DOWN;  break;
-        case 'C': if (direction != DIR_LEFT)  direction = DIR_RIGHT; break;
-        case 'D': if (direction != DIR_RIGHT) direction = DIR_LEFT;  break;
+    uint8_t c;
+    while (1) {
+        c = uart_recv();
+        if (c == 0) return;
+        switch (input_state) {
+            case 0:
+                input_state = (c == 0x1B) ? 1 : 0;
+                break;
+            case 1:
+                input_state = (c == '[' || c == 'O') ? 2 : 0;
+                break;
+            case 2:
+                switch (c) {
+                    case 'A': if (direction != DIR_DOWN)  direction = DIR_UP;    break;
+                    case 'B': if (direction != DIR_UP)    direction = DIR_DOWN;  break;
+                    case 'C': if (direction != DIR_LEFT)  direction = DIR_RIGHT; break;
+                    case 'D': if (direction != DIR_RIGHT) direction = DIR_LEFT;  break;
+                }
+                input_state = 0;
+                break;
+        }
     }
 }
 
@@ -195,6 +207,7 @@ void main(void) {
         uart_puts("GAME OVER  score: ");
         print_uint8(score);
         uart_puts("\r\npress any key\r\n");
-        uart_getc();
+        while (uart_recv() == 0);  /* wait for any byte */
+        input_state = 0;
     }
 }
-- 
cgit v1.3