;
; ws2812.pio
;
; WS2812B waveform generator. One PIO state machine clocks the 1.25us bit
; cell directly, which is what PIO is for - unlike the Circle build, which
; has to fake the waveform by streaming 8 SPI bytes per data bit.
;
; Timing per bit (T1+T2+T3 = 10 cycles = 1.25us, so the SM runs at 8MHz):
;	'0' = 0.4us high, 0.85us low
;	'1' = 0.8us high, 0.45us low
;
.program ws2812
.side_set 1

.define public T1 3
.define public T2 3
.define public T3 4

.wrap_target
bitloop:
    out x, 1        side 0 [T3 - 1]
    jmp !x do_zero  side 1 [T1 - 1]
do_one:
    jmp bitloop     side 1 [T2 - 1]
do_zero:
    nop             side 0 [T2 - 1]
.wrap

% c-sdk {
#include "hardware/clocks.h"

static inline void ws2812_program_init (PIO pio, uint sm, uint offset, uint pin, float freq)
{
	pio_gpio_init (pio, pin);
	pio_sm_set_consecutive_pindirs (pio, sm, pin, 1, true);

	pio_sm_config c = ws2812_program_get_default_config (offset);
	sm_config_set_sideset_pins (&c, pin);

	// 24 bits per LED, shifted out MSB first, auto-pulled a byte-triple at a time.
	sm_config_set_out_shift (&c, false, true, 24);
	sm_config_set_fifo_join (&c, PIO_FIFO_JOIN_TX);

	int cycles_per_bit = ws2812_T1 + ws2812_T2 + ws2812_T3;
	float div = clock_get_hz (clk_sys) / (freq * cycles_per_bit);
	sm_config_set_clkdiv (&c, div);

	pio_sm_init (pio, sm, offset, &c);
	pio_sm_set_enabled (pio, sm, true);
}
%}