feat: restore 3-bit SPI encoding at 3.0 MHz with zero-gap transmission to align with FCOB-2.7 clock rate

App/main.c

@@ -128,33 +128,29 @@ void UI_ShowSosPage(void);
  * WS2812B 幻彩 LED 单线驱动函数 (24MHz 1T 模式下精准时序控制)
  * ========================================================================= */
 
-void WS2812_EncodeByte5(u8 v, u8 *buf)
+const u16 code SPI_LUT[16] = {
-{
+    0x924, 0x926, 0x934, 0x936, 0x9A4, 0x9A6, 0x9B4, 0x9B6,
-    u8 p7 = (v & 0x80) ? 0x1C : 0x18;
+    0xD24, 0xD26, 0xD34, 0xD36, 0xDA4, 0xDA6, 0xDB4, 0xDB6
-    u8 p6 = (v & 0x40) ? 0x1C : 0x18;
+};
-    u8 p5 = (v & 0x20) ? 0x1C : 0x18;
-    u8 p4 = (v & 0x10) ? 0x1C : 0x18;
-    u8 p3 = (v & 0x08) ? 0x1C : 0x18;
-    u8 p2 = (v & 0x04) ? 0x1C : 0x18;
-    u8 p1 = (v & 0x02) ? 0x1C : 0x18;
-    u8 p0 = (v & 0x01) ? 0x1C : 0x18;
 
-    buf[0] = (p7 << 3) | (p6 >> 2);
+void WS2812_EncodeByte(u8 v, u8 *buf)
-    buf[1] = (p6 << 6) | (p5 << 1) | (p4 >> 4);
+{
-    buf[2] = (p4 << 4) | (p3 >> 1);
+    u16 p1 = SPI_LUT[v >> 4];
-    buf[3] = (p3 << 7) | (p2 << 2) | (p1 >> 3);
+    u16 p2 = SPI_LUT[v & 0x0F];
-    buf[4] = (p1 << 5) | p0;
+    buf[0] = p1 >> 4;
+    buf[1] = ((p1 & 0x0F) << 4) | (p2 >> 8);
+    buf[2] = p2;
 }
 
 void WS2812_Write24Bit(u8 g, u8 r, u8 b)
 {
-    u8 xdata buf[15];
+    u8 xdata buf[9];
     u8 i;
     u16 timeout;
     
-    WS2812_EncodeByte5(g, &buf[0]);
+    WS2812_EncodeByte(g, &buf[0]);
-    WS2812_EncodeByte5(r, &buf[5]);
+    WS2812_EncodeByte(r, &buf[3]);
-    WS2812_EncodeByte5(b, &buf[10]);
+    WS2812_EncodeByte(b, &buf[6]);
     
     EA = 0;
     
@@ -162,31 +158,31 @@ void WS2812_Write24Bit(u8 g, u8 r, u8 b)
     P2M1 &= ~((1 << 3) | (1 << 5));
     P2M0 |=  ((1 << 3) | (1 << 5));
     
-    SPCTL = 0xD0; // Enable SPI at SYSCLK/4 (6.0 MHz)
+    SPCTL = 0xD0; // Enable SPI at SYSCLK/4 (3.0 MHz actual clock on board)
     SPSTAT = 0xC0; // Clear flags
     
     SPDAT = buf[0]; // Goes to shift register immediately
-    // Wait about 20 system cycles (halfway through transmission) to avoid WCOL
+    // Wait about 20 system cycles to avoid WCOL
     _nop_(); _nop_(); _nop_(); _nop_(); _nop_(); 
     _nop_(); _nop_(); _nop_(); _nop_(); _nop_(); 
     _nop_(); _nop_(); _nop_(); _nop_(); _nop_(); 
     _nop_(); _nop_(); _nop_(); _nop_(); _nop_(); 
     SPDAT = buf[1]; // Goes to transmit buffer
     
-    for (i = 2; i < 15; i++)
+    for (i = 2; i < 9; i++)
     {
         timeout = 2000;
         while (!(SPSTAT & 0x80) && --timeout); // Wait with timeout
         SPSTAT = 0xC0;
-        SPDAT = buf[i];          // Write buf[i] to transmit buffer
+        SPDAT = buf[i];          // Write buf[i] to transmit buffer (zero gap!)
     }
     
     timeout = 2000;
-    while (!(SPSTAT & 0x80) && --timeout); // Wait for buf[13]
+    while (!(SPSTAT & 0x80) && --timeout); // Wait for buf[7]
     SPSTAT = 0xC0;
     
     timeout = 2000;
-    while (!(SPSTAT & 0x80) && --timeout); // Wait for buf[14]
+    while (!(SPSTAT & 0x80) && --timeout); // Wait for buf[8]
     SPSTAT = 0xC0;
     
     SPCTL = 0x90; // Disable SPI
@@ -1058,7 +1054,7 @@ void main(void)
             }
             else if (cmd == 't' || cmd == 'T')
             {
-                Uart_SendString("[UART SIM] SPI 6MHz Clock Test on P2.5 (SCLK) and P2.3 (MOSI) active. Press reset to exit.\r\n");
+                Uart_SendString("[UART SIM] SPI 3MHz Clock Test on P2.5 (SCLK) and P2.3 (MOSI) active. Press reset to exit.\r\n");
                 // Configure SCLK (P2.5) and MOSI (P2.3) as push-pull output
                 P2M1 &= ~((1 << 3) | (1 << 5));
                 P2M0 |=  ((1 << 3) | (1 << 5));