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feat: implement double-buffered glitch-free unrolled 3-bit SPI driver to guarantee continuous clock and zero glitches

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zouhaitao
2026-07-08 16:09:47 +08:00
parent fdbb165dc7
commit e6e81f48c0
1 changed files with 12 additions and 5 deletions
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17
App/main.c
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@@ -162,12 +162,17 @@ void WS2812_Write24Bit(u8 g, u8 r, u8 b)
P2M1 &= ~((1 << 3) | (1 << 5)); P2M1 &= ~((1 << 3) | (1 << 5));
P2M0 |= ((1 << 3) | (1 << 5)); P2M0 |= ((1 << 3) | (1 << 5));
SPSTAT = 0xC0; // Clear flags first SPSTAT = 0xC0; // Clear flags
SPCTL = 0xD0; // Enable SPI at SYSCLK/4 (3.0 MHz actual clock on board) SPCTL = 0xD0; // Enable SPI at SYSCLK/4 (3.0 MHz actual clock on board)
SPDAT = b0; // Send 0x00. MOSI remains low during startup delay!
// Unrolled 10-byte transmission with minimal gap (~300ns) SPDAT = b0; // Start transmitting dummy 0x00 (absorbs startup delay at MOSI=0)
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b1; // Wait at least 16 CPU cycles to ensure b0 has moved to the shifter
_nop_(); _nop_(); _nop_(); _nop_(); _nop_(); _nop_(); _nop_(); _nop_();
_nop_(); _nop_(); _nop_(); _nop_(); _nop_(); _nop_(); _nop_(); _nop_();
SPDAT = b1; // Buffer b1 (zero gap!)
// Transmission loop unrolled with double-buffering (zero gap SCLK)
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b2; while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b2;
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b3; while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b3;
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b4; while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b4;
@@ -176,7 +181,9 @@ void WS2812_Write24Bit(u8 g, u8 r, u8 b)
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b7; while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b7;
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b8; while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b8;
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b9; while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; SPDAT = b9;
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0;
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; // Wait for b8 to finish shifting, b9 moves to shifter
while (!(SPSTAT & 0x80)); SPSTAT = 0xC0; // Wait for b9 to finish shifting
SPCTL = 0x90; // Disable SPI SPCTL = 0x90; // Disable SPI
WS2812_DI = 0; WS2812_DI = 0;