ws2812 v0.1.0

Encode RGB pixels into the GRB byte order used by WS2812 strips.

Application scenarios

• A single WS2812 status LED on a product.
• A short LED strip for state, battery, or progress.
• A Padauk/CA51 project that already has a bit-banged WS2812 example.

Contract

typedef struct {
    void *context;
    void (*write_byte)(void *context, uint8_t byte);
    void (*reset)(void *context);
} ws2812_port_t;

void ws2812_init(ws2812_t *strip, ws2812_port_t port);
void ws2812_send_rgb(ws2812_t *strip, const uint8_t *rgb, uint16_t count);
void ws2812_send_grb(ws2812_t *strip, const uint8_t *grb, uint16_t count);

• rgb is three bytes per pixel: red, green, blue.
• write_byte sends one byte MSB first with the WS2812 bit timing.
• reset holds the line low for at least 50 us.
• No allocation.

Parameters

• The port owns the bit timing and the CPU clock dependency.
• count is the number of pixels; the buffer is 3*count bytes.

Memory and timing

• 8 bytes of state; O(count) bytes.
• Bit timing is in the adapter; the core only orders GRB bytes.

Integration

const uint8_t red[3] = {255, 0, 0};
ws2812_t strip;
ws2812_init(&strip, board_ws2812_port());
ws2812_send_rgb(&strip, red, 1);

Adapters

• Keep the timer, GPIO, interrupt masking, and reset timing in the adapter.
• Reference example: Padauk Module_Sensor/WS2812B.
• Do not copy vendor delay loops into the core.

When not to use

• APA102 or other clocked strips; they need a different protocol.
• Very long strips where DMA is required; the port can still implement DMA,

but the core remains byte-oriented.

Verification

make test covers GRB ordering, multiple pixels, GRB passthrough, and reset.

void *context;
void (*write_byte)(void *context, uint8_t byte);
void (*reset)(void *context);